Role of the thymus in control of autoreactivity or allotolerance in syngeneic and allogeneic bone marrow chimeras treated with bacterial adjuvants

Thy-1-bone marrow (BM) cells from C57BL/6 (B6) mice were transferred into thymectomized or non-thymectomized syngeneic B6----B6, allogeneic B6----C3H or semiallogeneic B6----(B6 X C3H)F1, irradiated mice, after which bacterial substances (bacillus Calmette Guérin [BCG] or Bordetella pertussis [Bp]) were administered within 3 days. The regulation of reactivity toward the host environment, i.e., autoresponsiveness in B6----B6 and allotolerance in B6---C3H, was investigated by monitoring a graft-vs-host (GvH)-like wasting syndrome, as well as the in vitro responsiveness of spleen cells from the reconstituted mice in a mixed leukocyte culture/cell-mediated lysis (MLC/CML) assay. The BCG-treated B6----B6 recipients developed a wasting syndrome and MLC/CML reactivity toward syngeneic target cells within 7 wk. This was never observed in BCG-treated but otherwise normal (i.e., nonreconstituted) mice, nor was it seen in any bone marrow chimeras that had been left without BCG treatment, irrespective of host/donor combination or thymectomy. The development of wasting syndrome as well as autoreactivity in BCG-treated B6----B6 mice could be prevented by thymectomizing the recipients before reconstitution or co-cultivating the donor BM cells with syngeneic spleen cells before reconstitution of nonthymectomized recipients. In the allogeneic or semiallogeneic combinations, the BCG treatment resulted in a wasting syndrome and CML/MLC reactivity toward C3H or (C3H X B6)F1 host-derived cells irrespective of thymic presence or absence. No breakdown of allotolerance, however, was retarded in the thymectomized mice, and it could be prevented by co-cultivation of donor BM cells with splenocytes of recipient genotype only if the cells were used to reconstitute thymectomized recipients. The breakdown of allotolerance in B6----C3H chimera was never accompanied by autoreactivity against B6 target cells. It is concluded that induction of autoreactivity and GvH in BCG-treated syngeneic BM chimeras, probably reflecting the breakdown of autotolerance, is strictly thymus dependent. In contrast, induction of anti-host reactivity in BCG-treated allogeneic chimeras may occur in the absence of a thymus and without concomitant autoreactivity, suggesting two independent levels of controls: one that is thymus dependent for the breakdown of auto- as well as allotolerance, and one that is thymus independent, unique for the breakdown of allotolerance.     

Transfection and expression of syngeneic H-2 genes does not reduce malignancy of H-2 negative teratocarcinoma cells in the autologous host

Rejection of the MHC class I negative 402AX teratocarcinoma is accompanied by induction of tumor cell-encoded H-2K and H-2D antigens by the genetically resistant host. To determine whether MHC antigen expression is required for 402AX rejection, we have prepared H-2Db-transfected 402AX cells (402AX/Db). Transfectants express high levels of H-2Db, most of which is not associated with beta 2-microglobulin. MHC syngeneic and allogeneic mice susceptible to 402AX are resistant to 402AX/Db, suggesting that MHC class I antigen expression is required for tumor rejection. Autologous 129 hosts, however, are susceptible to 402AX/Db. 402AX cells transfected with the H-2Kb gene (402AX/Kb) are also lethal in the autologous 129/J host, but rejected by MHC syngeneic and allogeneic mice. Non-129 strain 402AX-susceptible mice pre-immunized with 402AX/Db or simultaneously challenged with 402AX/Db plus 402AX are immune to 402AX. Mice immunized with 402AX/Db produce MHC class I induction factor. 402AX/Db and 402AX cells are lysed equally by natural killer cells, indicating that in 402AX cells the expression of class I antigens is unrelated to NK susceptibility. These studies confirm the requirement for class I expression in 402AX immunity, but demonstrate that in the autologous host immunity requires additional factors beyond class I antigen expression.     

Altered donor and recipient Ly49+ NK cell subsets in allogeneic H-2d --> H-2b and H-2b --> H-2d bone marrow chimeras

NK cells reject non-self hematopoietic bone marrow (BM) grafts via Ly49 receptor-mediated MHC class I-specific recognition and calibration of receptor expression levels. In this paper we investigated how Ly49+ subset frequencies were regulated dependent on MHC class I expression. The development of donor and host Ly49A+ (recognizes H-2Dd and H-2Dk ligands) and Ly49C/I+ (Ly49CBALB/c recognizes H-2Kb, H-2Kd, and H-2Dd, and Ly49CB6 recognizes only H-2Kb) NK cell frequencies were monitored for 120 days in murine-mixed allogeneic BM chimeras. C57BL/6 (H-2b) BM was transplanted into BALB/c (H-2d) mice and vice versa. Peripheral NK cell populations were examined every 5 days. Chimerism was found to be stable with 80-90% donor NK cells. In contrast to syngeneic controls reexpressing pretransplant patterns, donor and host NK cells revealed new and mainly reduced subset frequencies 55 days after allogeneic transplantation. Recipient NK cells acquired these later than donor NK cells. In H-2d --> H-2b chimeras Ly49A+, Ly49C/I+, and Ly49A+/Ly49C/I+ proportions were mainly diminished upon interaction with cognate ligands. Also in H-2b --> H-2d chimeras, Ly49A+ and Ly49A+/Ly49C/I+ subsets were reduced, but there was a transient normalization of Ly49C/I+ proportions in the noncognate host. After 120 days all subsets were reduced. Therefore, down-regulation of developing Ly49A+ and Ly49C/I+ chimeric NK cell frequencies by cognate ligands within 7-8 wk after BM transplantation may be important for successful engraftment.     

Studies of H-2 restriction in cell-mediated cytotoxicity and transplantation immunity to Leukemia-associated antigens.

H-2 dependency of T cell-mediated cytotoxicity and transplantation immunity to leukemia-associated antigens has been investigated. Through the use of a 20-hr 125IUdR release assay, it was found that the induction of T cell-mediated cytotoxicity against Friend virus-induced leukemias of different H-2 haplotype orgins could be produced by immunization with both syngeneic and allogeneic tumor cells; the effector cells that were generated by syngeneic immunization could also provide effective killing of allogeneic tumor cells, although the killing of allogeneic targets might require a longer incubation time (20 to 40 hr). Furthermore, in vivo transplantation immunity against Friend virus-induced leukemias also was induced by immunization with both syngeneic and allogeneic tumors and syngeneic immunization could induce specific protection against the challenge with a-logeneic tumor in x-irradiated hosts. These findings clearly indicate that, both at the sensitizing phase and effector phase of the immune response, there is no strict H-2 dependency for T cell-mediated cytotoxicity or in in vivo transplantation imunity to leukemia-associated antigens.     

Induction of linked suppression in addition to the donor H-2 class I-specific unresponsiveness in recipient T cells by transfusing class I plus class II-disparate, but not class I alone-disparate, bone marrow cells

This study was undertaken to determine whether bone marrow (BM) cells contain a cell population with the capacity to induce an unresponsiveness of T cells specific to the BM self-H-2 class I antigens in vivo, i.e., veto cell population. Recombinant or congenic mice were infused intravenously with H-2-incompatible BM cells. One to several weeks later, donor H-2-and irrelevant H-2-specific responses in mixed lymphocyte reaction cultures of recipient T cells were assessed. Transfusion of H-2-incompatible BM of C57BL/10 (B10) recombinant strains caused a long-lasting cytotoxic T lymphocyte (CTL) unresponsiveness to the donor class I antigens in recipient lymph node cells. When class I plus class II-disparate BM cells were transfused, an anti-donor class I CTL response and a response against a third-party class I antigen, which was presented on the stimulator cells coexpressing the donor class I and class II, were significantly suppressed. This linked suppression lasted for less than 2 weeks after transfusion. Transfusion of class I-alone-disparate BM induced the donor class I-specific CTL unresponsiveness, but not the linked suppression. The induction of linked suppression was prevented considerably by transfusing nylon wool-nonadherent BM or by treating recipients with cyclophosphamide 2 days before transfusion. An anti-third-party class I CTL response, stimulated in vitro with fully allogeneic spleen cells, was not hampered by the BM transfusion. Coculturing the lymph node (LN) cells obtained from the class I plus class II-disparate BM recipient with normal LN cells interfered with the generation of both anti-donor class I and anti-linked third-party class I CTL, whereas, coculturing LN cells from the class I alone-disparate BM recipient inhibited neither specificity of CTL generation. Transfusion of class I plus class II-disparate BM resulted in a significant suppression of the donor class II-specific proliferative response. In contrast, transfusion of class I alone-disparate BM did not suppress any proliferative responses, including even a "linked" third-party class II-specific response. Transfusion of bm 1, (B6 X bm 1)F1, or (bm 1 X bm 12)F1 BM to B6 did not induce unresponsiveness in bm 1-specific CTL responses. However, the transfusion resulted in a significant suppression of bm 1-reactive proliferative response of recipient LN cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunogenetic analysis of tolerance induction in anti-alloantigen delayed type hypersensitivity responses by portal venous pre-inoculation with allogeneic cells

The present study investigates some of the immunogenetic bases for tolerance of anti-allo-delayed type hypersensitivity (DTH) responses as induced by pre-inoculating allogeneic cells via portal venous (p.v.) route. BALB/c mice were injected with totally allogeneic C57BL/6 or H-2 incompatible BALB.B spleen cells via p.v. route. These mice not only failed to exhibit anti-H-2b DTH responses, but also abrogated the potential to generate H-2b-specific DTH responses as induced by the subsequent immunization with H-2b spleen cells via subcutaneous (s.c.) route. The p.v. presensitization with allogeneic spleen cells differing at either class I or class II of major histocompatibility complex (MHC) resulted in the tolerance induction of DTH responses to the respective allogeneic class I or class II MHC antigens. Moreover, the p.v. administration of the class I-positive allogeneic cell fraction depleted of class II-positive component into recipients differing at both class I and class II was capable of inducing anti-class I DTH tolerance. These results indicate that anti-allo-class I or class II DTH tolerance can be induced independently and that the existence of class II antigens on p.v.-presensitized cells is not necessarily required for the tolerance induction of anti-allo-class I DTH response.     

Implantation of cultured thymic fragments in congenitally athymic nude rats: ignorance of thymic epithelial haplotype in generation of alloreactivity

We studied the development of thymus-dependent immunity in congenitally athymic nude rats after implantation of cultured thymic fragments (CTF), particularly the development of in vitro alloreactivity in allogeneic combinations. CTF of DA (RT1a), PVG (RT1c), and RP (RT1p(u,1] origin were implanted in nude rats of WAG (RT1u) origin. In analysis 14 to 18 wk later, all recipients exhibited thymus-dependent immunocompetence assessed by (immuno)-histology of lymphoid organs and responsiveness to in vitro concanavalin A stimulation and in vivo ovalbumin immunization. Control nude animals were unresponsive. Also, in vitro alloreactivity was observed, measured by mixed lymphocyte reaction and cell-mediated lympholysis. The alloresponse to the allogeneic CTF donor haplotype was as to a third party, but that to the recipient was negative. The CTF before implantation were devoid of lymphoid elements and revealed epithelial-like cells as the major component. Cells in CTF showed expression of RT1 class I and class II antigens. CTF at autopsy had the architecture of a normal thymus. In immunohistochemistry using haplotype-specific antibodies, lymphocytes showed RT1u class I expression as in the normal WAG thymus. In the cortex-like area of CTF, stromal cells revealed class I and class II haplotype expression of the donor thymus, but in the medulla-like area, class II haplotype expression was that of the recipient WAG rat. These data indicate that after implantation in nude rats, CTF become populated not only with lymphoid elements, but also with stromal components from the recipient. In induction of thymus-dependent immunity, these acceptor-derived stromal (dendritic) cells may be involved in generation of allospecificity; class I and class II haplotype expression by the donor cortex (epithelial) compartment is ignored in this process.     

Functional heterogeneity in allospecific cytotoxic T lymphocyte clones. II. Development of syngeneic cytotoxicity in the absence of specific antigenic stimulation

Two out of four long-term murine allospecific cytotoxic T lymphocyte (CTL) clones tested could develop high levels of cytotoxicity against syngeneic target cells when cultured under appropriate conditions. All CTL clones maintained strict allospecificity so long as they were cultured with both appropriate allogeneic stimulator cells and growth factor (supernatant from secondary mixed lymphocyte cultures). In two of the clones, syngeneic reactivity rapidly developed when the allogeneic stimulator cells were replaced with syngeneic or third party stimulator cells, and when the supernatant from EL4 thymoma cells stimulated with phorbol ester was used as growth factor. In addition to killing the appropriate allogeneic target, clones with syngeneic reactivity could kill both syngeneic C57BL/6 targets and H-2-congenic BALB.B targets but not third party unrelated targets, suggesting that the self structure recognized was coded for within the major histocompatibility complex. Such clones did not kill the natural killer (NK) target YAC. The results obtained from cold target inhibition and from subcloning at limiting dilution of clones with syngeneic reactivity suggested that both allogeneic and syngeneic reactivity could be expressed by the same individual cell in the CTL clone. The specificity for syngeneic H-2 as opposed to third party H-2 and NK-sensitive target cells, and the observation that both allospecific and syngeneic killing could be partially blocked by anti-Lyt-2 antibody treatment of the CTL, strongly suggested that different recognition structures are involved in CTL-mediated syngeneic cytotoxicity and NK cytotoxicity.     

Specific T-cell-mediated killing of autologous lung tumour cells

The phenomenon that strong syngeneic T-cell-mediated cytotoxicity is observed if killer, stimulator, and target cells share H-2 histocompatibility antigens is called H-2 restriction. Here a syngeneic model system making use of hapten-coupled stimulator and target cells is used to explore whether H-2 restriction is absolute or not. Using TNP-coupled spleen or tumor cells as stimulator or target cells in syngeneic and allogeneic situations, it is shown that neither the induction step nor the effector step of TNP-dependent killing is H-2 restricted. By varying the experimental assay conditions more or less H-2-restricted, TNP-dependent killing can be observed. For instance, suboptimal coupling of TNP to targets may result in H-2-restricted killing. Similarly, the use of spleen cell targets as opposed to spleen blast cells or tumor cells may result in H-2-restricted lysis. In contrast optimal coupling of TNP to sensitive target cells and coupling of TNP to cells with certain H-2 haplotypes may lead to significant TNP-dependent killing which is not H-2 restricted. Since hapten-coupled cells lacking H-2 are neither stimulators nor targets these results suggest that the T-cell receptor recognizes TNP-modified H-2 antigens simply as nonself-H-2. Thus hapten coupling of syngeneic cells appears to lead to a histocompatibility antigen change similar to the situation in an allogeneic cytotoxic reaction. Experiments are presented which support this view showing that TNP-coupled and uncoupled syngeneic or allogeneic stimulator and target cells cross-react. For instance allogeneic sensitization may lead to killing on TNP-coupled targets syngeneic to the effector cells and TNP-coupled stimulator cells syngeneic to the effector cells may induce killing on uncoupled syngeneic targets. TNP-dependent cytotoxicity can therefore be envisaged as a kind of allogeneic reactivity due to modification of H-2 antigens by the TNP coupling. This conclusion may have bearing on other model systems in which syngeneic killing appears to be H-2 restricted. In support of this possibility it is shown that allogeneic sensitization may lead to priming of memory cells able to respond to minor histocompatibility antigens.     

Effect of selective T cell depletion of host and/or donor bone marrow on lymphopoietic repopulation, tolerance, and graft-vs-host disease in mixed allogeneic chimeras (B10 + B10.D2----B10)

Reconstitution of lethally irradiated mice with a mixture of T cell-depleted syngeneic plus T cell-depleted allogeneic bone marrow (B10 + B10.D2----B10) leads to the induction of mixed lymphopoietic chimerism, excellent survivals, specific in vivo transplantation tolerance to subsequent donor strain skin grafts, and specific in vitro unresponsiveness to allogeneic donor lymphoid elements as assessed by mixed lymphocyte reaction (MLR) proliferative and cell-mediated lympholysis (CML) cytotoxicity assays. When B10 recipient mice received mixed marrow inocula in which the syngeneic component had not been T cell depleted, whether or not the allogeneic donor marrow was treated, they repopulated exclusively with host-type cells, promptly rejected donor-type skin allografts, and were reactive in vitro to the allogeneic donor by CML and MLR assays. In contrast, T cell depletion of the syngeneic component of the mixed marrow inocula resulted in specific acceptance of allogeneic donor strain skin grafts, whether or not the allogeneic bone marrow was T cell depleted. Such animals were specifically unreactive to allogeneic donor lymphoid elements in vitro by CML and MLR, but were reactive to third party. When both the syngeneic and allogeneic marrow were T cell depleted, variable percentages of host- and donor-type lymphoid elements were detected in the mixed reconstituted host. When only the syngeneic bone marrow was T cell depleted, animals repopulated exclusively with donor-type cells. Although these animals had detectable in vitro anti-host (B10) reactivity by CML and MLR and reconstituted as fully allogeneic chimeras, they exhibited excellent survival and had no in vivo evidence for graft-vs-host disease. In addition, experiments in which untreated donor spleen cells were added to the inocula in this last group suggest that the presence of T cell-depleted syngeneic bone marrow cells diminishes graft-vs-host disease and the mortality from it. This system may be helpful as a model for the study of alloresistance and for the identification of syngeneic cell phenotypes, which when present prevent engraftment of allogeneic marrow.     

Driving adenovirus type 12-transformed BALB/c mouse cells to express high levels of class I major histocompatibility complex proteins enhances, rather than abrogates, their tumorigenicity.

The tumorigenicity of adenovirus type 12 (Ad12)-transformed cells has been attributed to the low levels of class I major histocompatibility complex (MHC) protein expression by these cells. These levels of class I proteins are thought to be below the threshold critical for cytotoxic T-lymphocyte recognition, a process that may be involved in tumor cell immunosurveillance. We have used gene transfer experiments to investigate the role played by class I protein expression in the tumorigenicity of Ad12-transformed BALB/c mouse cells in naive, syngeneic adult mice. Our Ad12-transformed mouse cells were tumorigenic in adult mice and were similar to other Ad12-transformed mammalian cells in that they expressed low levels of class I MHC mRNA and cell surface proteins. Despite these low levels of expression, the cells were highly immunogenic in syngeneic mice and were rejected as allografts by allogeneic mice. Transfection of genomic H-2Dd or H-2Ld fragments into these cells produced a variety of cell clones that expressed increased levels of cell surface class I proteins. These cells expressing high levels of class I protein were up to 16-fold more tumorigenic than the parental cells in syngeneic adult mice. Thus, by quantitative assays, the tumorigenicity of Ad12-transformed BALB/c mouse cells is not functionally related to the low levels of class I MHC proteins they express. The increased tumorigenicity expressed by H-2Dd- and H-2Ld-transfected cells was not detected in BALB/c nu/nu mice, suggesting that a thymus-dependent mechanism that is not mediated by evasion of cytotoxic T-lymphocyte recognition could contribute to the difference in tumorigenicity of Ad12-transformed BALB/c mouse cells that express low and high levels of class I MHC proteins.     

Allo-I-J determinants participate in maintenance of neonatal H-2 tolerance

To evaluate the role of IJ antigens in maintenance of the tolerant state in adult H-2 tolerant mice, we have attempted to abolish tolerance by injecting monoclonal antibodies (mab) specific for host, donor, or third party IJ antigens into adult H-2 tolerant mice. Abolition of tolerance was evidenced by the rejection of fresh test skin grafts bearing the tolerated antigens. Whole H-2 tolerant mice treated with anti-IJ mab specific for donor (allo) IJ antigens rejected their test skin grafts, indicating that tolerance had been abolished. When two other types of tolerant mice were tested, we found that mice tolerant of class II antigens alone, but not mice tolerant of an IJ thru D disparity, were susceptible to the anti-donor IJ mab treatment. In addition, adult tolerant mice were unaffected by treatment with either anti-host or anti-third party IJ mab. When tested in vitro, lymphoid cells from tolerant mice, the tolerance of which was abolished by anti-IJ mab, remained unresponsive to the tolerogen, just as untreated (control) tolerant mice, in several in vitro assays (e.g., mixed lymphocyte reaction, cytotoxic T cell precursor frequency and bulk cell-mediated lysis without growth factor). Mice treated with antidonor IJ mab, however, unlike mice treated with anti-host or third party IJ mab, were capable of generating tolerogen-specific T cells in the absence of exogenous growth factor. Thus in the strain combinations we used, adult mice tolerant of either the entire H-2 region or of the class II major histocompatibility complex region alone are susceptible to abolition of the tolerant state by treatment with anti-donor IJ mab. Coincidentally, lymphoid cells from these mice generate sufficient endogenous T helper activity to activate the tolerogen-specific cytotoxic T cells. We suspect that these latter cells may be responsible for rejection of grafts bearing the tolerated antigens.     

The cellular mechanism of maintenance of neonatally induced tolerance to H-2 class I antigens

We used limiting dilution analysis protocols to investigate the mechanism by which in vitro cytotoxic T lymphocyte (CTL) hyporeactivity is maintained in adult mice that had been neonatally tolerized to major histocompatibility complex-encoded antigens. Class I molecules, presented on donor cells having an H-2 K or D region haplotype difference from recipients, readily induce tolerogen-specific CTL hyporeactivity. All attempts to identify any in vitro effects of active suppressive cells operative in the maintenance of this hyporeactivity have been unsuccessful. We conclude that this cytotoxic deficiency is the consequence of in vivo mediated clonal inactivation of the precursors of tolerogen-specific CTL. A presentation and evaluation of the assumptions inherent in this conclusion are made. In contrast to class I molecules, class II molecules, presented on donor cells having an H-2 I region haplotype difference from recipients, are unable to induce tolerogen-specific CTL hyporeactivity, even when injected neonatally at high doses. This inability of class II molecules to induce CTL tolerance parallels the considerable difficulty of inducing helper T lymphocyte tolerance to class II molecules.     

Specific and nonspecific infiltration of sponge matrix allografts by specifically sensitized cytotoxic lymphocytes

Urethane sponges coated with allogeneic or syngeneic cells were implanted subcutaneously into mice and the cytotoxicity of infiltrating host cells was assessed in vitro. First-set allogeneic sponges attracted a population of lymphocytes enriched in cytotoxic T cells directed against the alloantigens in the sponge. If two sponges bearing cells of different H-2 specificity were grafted simultaneously to a single recipient, specifically sensitized cytotoxic cells (SSCL) were found in both sponges directed against both sets of alloantigens, although specific infiltration predominated. If a syngeneic and allogeneic sponge were transplanted, SSCL were found in both the syngeneic sponge and allogeneic sponge. These data are interpreted to suggest that chemotactic substances are elaborated at graft sites which can attract circulating SSCL into sites of inflammation and that those released at the specific site are more attractive for SSCL than are those elaborated at sites of nonspecific rejection or healing. In recipients who had previously been sensitized to alloantigens, second-set grafts were rapidly infiltrated by SSCL directed against the sensitizing antigen. First-set indifferent allografts in sensitized recipients were infiltrated by SSCL directed against the previous alloantigens as well as SSCL directed against its own alloantigens. Syngeneic grafts were not infiltrated by SSCL in presensitized recipients. These data suggest that any alloantigenic stimulus can induce the mobilization from lymphoid depots of preformed SSCL directed against another set of antigens; syngeneic grafts cannot. Once mobilized, however, circulating SSCL can respond to specific and nonspecific chemotactic factors elaborated by either healing or rejecting grafts.     

Co-expression of immunogenic determinants by the same cellular immunogen is required for the optimum immunotherapeutic benefit in mice with melanoma

 Tumor-associated T cell epitopes are recognized by T cells in the context of determinants specified by class I loci. Since the rejection of foreign histocompatibility antigens is known to enhance tumor immunity, immunization with a cellular vaccine that combined the expression of both syngeneic and allogeneic class I determinants could have important immunological advantages over a vaccine that expressed either syngeneic or allogeneic determinants alone. To investigate this question in a mouse melanoma model system, we tested the immunotherapeutic properties of B16 melanoma × LM fibroblast hybrid cells in C57BL/6J mice with melanoma. Like C57BL/6J mice, B16 cells expressed H-2K^b class I determinants and (antibody-defined) melanoma-associated antigens. LM cells, of C3H mouse origin, formed H-2K^k determinants along with B7.1, a co-stimulatory molecule that can activate T cells. The B16 × LM hybrid cells co-expressed H-2K^b and H-2K^k class I determinants, B7.1 and the melanoma-associated antigens. C57BL/6J mice with melanoma, immunized with the semi-allogeneic hybrid cells, developed CD8-mediated melanoma immunity and survived significantly (P<0.005) longer than mice with melanoma immunized with a mixture of the parental cell types. The failure of melanoma immunity to develop in mice injected with the mixture of parental cells indicated that co-expression of the immunogenic determinants by the same cellular immunogen was necessary for an optimum immunotherapeutic effect. Augmented immunity to melanoma in mice immunized with the semi-allogeneic hybrid cells points toward an analogous form of therapy for patients with melanoma. Received: 19 May 1997 / Accepted: 23 July 1997     

Anti-bacterial immunity to Listeria monocytogenes in allogeneic bone marrow chimera in mice

Protection and delayed-type hypersensitivity (DTH) to the facultative intracellular bacterium Listeria monocytogenes (L.m.) were studied in allogeneic and syngeneic bone marrow chimeras. Lethally irradiated AKR (H-2k) mice were successfully reconstituted with marrow cells from C57BL/10 (B10) (H-2b), B10 H-2-recombinant strains or syngeneic mice. Irradiated AKR mice reconstituted with marrow cells from H-2-compatible B10.BR mice, [BR----AKR], as well as syngeneic marrow cells, [AKR----AKR], showed a normal level of responsiveness to the challenge stimulation with the listeria antigens when DTH was evaluated by footpad reactions. These mice also showed vigorous activities in acquired resistance to the L.m. By contrast, chimeric mice that had total or partial histoincompatibility at the H-2 determinants between donor and recipient, [B10----AKR], [B10.AQR----AKR], [B10.A(4R)----AKR], or [B10.A(5R)----AKR], were almost completely unresponsive in DTH and antibacterial immunity. However, when [B10----AKR] H-2-incompatible chimeras had been immunized with killed L.m. before challenge with live L.m., these mice manifested considerable DTH and resistance to L.m. These observations suggest that compatibility at the entire MHC between donor and recipient is required for bone marrow chimeras to be able to manifest DTH and protection against L.m. after a short-term immunization schedule. However, this requirement is overcome by a preceding or more prolonged period of immunization with L.m. antigens. These antigens, together with marrow-derived antigen-presenting cells, can then stimulate and expand cell populations that are restricted to the MHC (H-2) products of the donor type.     

Characterization of a CD4-positive T-cell line derived from an athymic (nu/nu) mouse.

We have isolated a Thy-1+, CD3+, CD4+ T-cell line from the spleen of a 12-week-old nu/nu (nude) BALB/c mouse. The cell line is clonal, and it expresses an alpha beta T-cell antigen receptor. Upon activation, these cells secrete IL-2 but not IL-4, putting them in the Th1 category. The cells can be triggered to proliferate and secrete lymphokines in the presence of irradiated syngeneic or allogeneic splenic feeder cells that express a variety of MHC haplotypes. This response is MHC class II-specific, because it can be blocked by either anti-Ia or anti-CD4 antibodies. From the response pattern of this T-cell line, we conclude that it recognizes a common determinant on class II MHC antigens. This nude mouse T-lymphocyte presumably has not undergone thymic selection. Therefore its unique specificity may reflect both the bias of T-cell antigen receptor genes for encoding receptors that recognize MHC molecules and the requirement for functional thymic epithelial cells for the efficient education of a self-MHC-restricted repertoire.     

Split tolerance in nude mice transplanted with 2'-deoxyguanosine-treated allogeneic thymus lobes

To elucidate the acquisition of self tolerance in the thymus, full-allogeneic thymic chimeras were constructed. Athymic C3H and BALB/c nude mice were reconstituted with the thymic lobes of BALB/c and B10.BR fetuses, respectively, that were organ cultured for 5 days in the presence of 2'-deoxyguanosine. T cells in these chimeras were tolerized to the host MHC in both MLR and CTL assays. In contrast, T cells in the chimeras exhibited split tolerance for the thymic MHC haplotype. CTL specific for class I MHC of the thymic haplotype were generated not only from the peripheral T cells of the chimeras but also from thymocytes re-populated in the engrafted thymic lobes. However, T cells in these chimeras responded poorly to the class II MHC of the thymic haplotype in a standard MLR assay. In a syngeneic MLR culture upon stimulation with enriched APC of the thymic haplotype, only 22 to 48% of the responses were mediated by CD4+ cells, and proliferations of CD4- cells were prominent. There were no haplotype-specific suppressor cells detected which would cause the unresponsiveness to the thymic class II MHC. These results indicated that the thymic lobes treated with 2'-deoxyguanosine were defective in the ability to induce the transplantation tolerance for the class I MHC expressed on the thymus, although the same thymic lobes were able to induce the transplantation tolerance for the thymic class II MHC.     

Genetic control of the immune response to collagen. III. Coordinate restriction of cellular cooperation and antigen responsiveness by thymus-directed maturation

The H-2 restriction of T helper cells from thymus-reconstituted nude mice was examined. Hybrid athymic mice were bred from BALB/c.nu and C57BL/6.nu parental strains and reconstituted with fetal thymus tissue from either parental strain. T helper cells from these mice, immunized to SRBC, were restricted to cooperation with B cells of the thymic H-2 haplotype. These T helper cells were shown to have originated from the F1 host by functional sensitivity to antisera and complement. The H-2 restriction of thymus-reconstituted F1 nude mice was further investigated by examining expression of the Ir-collagen phenotype. Results showed that the level of antibody produced in response to type I calf collagen in thymus chimeras correlates with the H-2 haplotype (high responder or low responder) of the reconstituting thymus. These experiments indicate that the thymus environment of T cell maturation influences both the H-2 restriction and Ir-phenotype of a responding immune system.     

Stimulation of genetic resistance to marrow grafts in mice by interferon-alpha/beta

Lethally irradiated mice were infused with syngeneic, H-2 allogeneic, parental strain, or H-2 heterozygous bone marrow cells. They were injected daily with rabbit anti-mouse interferons (IFN)-alpha/beta or gamma or with IFN-alpha/beta. The growth of donor-derived cells was judged 5 days later by measuring splenic incorporation of 5-iodo-2'-deoxyuridine-125I into DNA. Antibodies to IFN-alpha/beta, but not to IFN-gamma, weakened genetic (both hybrid and allogeneic) resistance to marrow cell grafts. IFN-alpha/beta stimulated hybrid and allogeneic resistance, the latter even in genetically "poor responder" mice. Mice pretreated with silica, which weakens genetic resistance, were stimulated by IFN-alpha/beta to resist incompatible marrow cell grafts; however, IFN-alpha/beta failed to reverse the effects of antiasialo GM1 serum on marrow graft rejection. IFN-alpha/beta did not inhibit the growth of syngeneic marrow cells and did not stimulate resistance to H-2 heterozygous bone marrow cells. We propose that genetic resistance occurs in two discrete steps. In the first step, hemopoietic histocompatibility (Hh) antigens are recognized by one host cell type, and this recognition leads to IFN-alpha/beta secretion by a silica-sensitive cell. In the second step, asialo GM1-positive natural killer cells stimulated by IFN-alpha/beta recognize Hh antigens on marrow stem cells and cause rejection. The defects in resistance observed in genetically poor responder mice and in mice treated with silica appear to involve the first step in recognition. The lack of rejection of H-2 heterozygous (Hh-) marrow cells by parental strain mice injected with IFN-alpha/beta indicated that specific Hh recognition is critical in the second step of genetic resistance.