H-2 unrestricted cytotoxic T cell activity against antigens controlled by genes in the QA/TLA region.

The specificity of H-2 unrestricted cytotoxic T cells was analyzed in secondary CML responses. A/J strain effector cells, sensitized against A.Tlab lymphoid cells, lysed target cells from strains with differing H-2 haplotypes but all sharing Qa-1b/Tlab alleles; whereas, target cells from strains with Qa-1a/Tlaa were not. When B6.Tlaa animals were in vivo-primed and challenged in vitro with B6 stimulator cells, no cytotoxic effector cell activity was generated. However, if B6.Tlaa animals were primed in vivo with A.BY cells and then rechallenged in vitro with either A.BY or B6 stimulator cells, cytotoxic effector cells were generated that lysed target cells from strains with Qa-1b/Tlab alleles. This suggests that factors in addition to Qa/Tla may play a role in the generation of anti-Qa/Tla effector cell activity. It was also noted that targets from strains with Qa-1a/Tlaa alleles were killed, although to a much lesser extent than the Qa-1b/Tlab targets. SWR anti-DBA/1 efffector cells strongly lysed target cells frrom strains with Qa-1b/Tlab, lysed Qa-1a/Tlaa targets to a lesser extent, and produced no cytotoxic effect on B6.Tlaa target cells. These data suggest that in addition to a CML target antigen associated with Qa-1b/Tlab, there may be an additional specificity recognized by cytotoxic T cells controlled by a gene outside of Qa-1b/Tlab.     

Studies on the induction and expression of T cell-mediated immunity. IV. Non-overlapping populations of alloimmune cytotoxic lymphocytes with specificity for tumor-associated antigens and transplantation antigens.

Two non-overlapping populations of alloimmune cytotoxic T cells with specificity for tumor-associated antigens (TAA) and for histocompatibility antigens (H-2) were characterized by two independent methods. The heterogeneity of cytotoxic cells was demonstrated in spleen cells derived from BALB/c (H-2d) mice sensitized to EL-4 (H-2b) tumor and from C57BL/6 (H-2b) mice sensitized to G-35 (H-2d) tumor cells. Adsorption of immune lymphocytes on monolayers prepared with cells bearing the sensitizing H-2 antigens abrogated the in vitro cell-mediated cytotoxicity (CMC) directed against 51Cr-labeled normal target cells (spleen cells or ConA-activated spleen blasts), whereas significant cytolytic activity to the corresponding 51Cr-tumor cells was still retained. Likewise, in competitive inhibition assays, CMC to 51 Cr-tumor target cells was only partially inhibited by unlabeled normal cells, whereas CMC to 51Cr-normal target cells was completely abrogated. These results suggested that alloimmune cytotoxic lymphocytes are heterogeneous and can be subdivided into two independent populations of restricted specificity. Several experiments suggested that the effector cell population directed against TAA can no longer elicit a graft-vs-host (GVH) reaction in vivo. This was demonstrated by adoptive transfer into lethally-irradiated allogeneic recipients of cytotoxic or primed spleen cells fractionated on host target cell monolayers. Furthermore, these results demonstrated that both effector cells and memory cells possess high affinity binding receptors to corresponding H-2 antigens. The potential use of fractionated immune lymphocytes sensitized to tumor allografts in adoptive immunotherapy is discussed.     

Immunogenetic analysis ofH-2 mutations

Spleen cells carrying theH-2K ^b allele and sensitized against TNP-modified stimulator cells in vitro displayed a cytotoxic effect against TNP-modified target cells carrying a mutation in theH-2K ^b allele (haplotypesH-2 ^ba ,H-2 ^bd , andH-2 ^bf ). Similar crossreactivity in TNP-CML was observed in the reciprocal direction. Spleen cells carrying theH-2K ^k allele and sensitized against TNP-modified stimulators displayed a cytotoxic effect against TNP-modified target cells carrying a mutation in theH-2K ^k allele (haplotypeH-2 ^ka ) and vice versa. The effector cells in these assays were sensitive to anti-T cell serum in the presence of complement, and supernatants from immune cultures did not induce nonimmune cells to display a cytotoxic effect. Titration of effector cells from mutant and wild-type strains of theH-2 ^b haplotype indicated no detectable quantitative differences in their activities. These data demonstrate that crossreactivity in TNP-CML occurs in closely related allogeneic strains that have recently undergone mutation in theH-2 complex.     

Inhibition of tumor growth mediated by lymphocytes sensitized in vitro to a syngeneic murine teratocarcinoma 402AX

TerC, a cell line derived from a strain 129 teratocarcinoma 402AX, was used to sensitize syngeneic 129 (H-2bc) splenic lymphocytes in vitro. The effector cells generated inhibited in vitro growth of TerC as measured by an 125I-IUDR ost-labeling technique. It was also shown, with a modified Winn assay, that the sensitized cells were effective in preventing TerC growth in vivo. The effector lymphocyte was nonadherent to nylon wool was sensitive to anti-Thy-1.2 + C, and was phenotypically Ly 1-2+. The anti-TerC effector T lymphocytes were not functional in a 51Cr-release assay. However, this failure to lyse appears not to be due to some intrinsic membrane resistance since both BCG and ConA-activated killers were able to lyse TerC. The TerC-sensitized lymphocytes displayed no H-2 restriction and were able to growth inhibit in vitro a wide range of tumorigenic cell lines, e.g., P815 (H-2d), EL-4 (H-2b),Sal (H-2a), and BALB/c (H-2d) 3T12. Mouse blastocyst cell lines were also inhibited. BALB/c 3T3 and mouse fibroblast cell strains were not growth inhibited. Thus, it appears that oncofetal antigens expressed on TerC are capable of initiating a cell-mediated response and that these antigenic specificities are shared by many transformed cell lines.     

Priming for a cytotoxic response to minor histocompatibility antigens: antigen specificity and failure to demonstrate a carrier effect.

Spleen cells from normal mice do not give a detectable in vitro cytotoxic T cell (CTL) response to minor H antigens. Spleen cells from animals primed in vivo with minor H antigens give a strong CTL response when boosted in culture with the appropriate stimulating cells. Here I have studied the requirements for priming a CTL response to minor H antigens. It is shown that priming is just as antigen specific as is cytolytic effector function. That is, priming cells have to carry the same minor antigens as the challenge cells. Inducing a graft-vs-host reaction in vivo does not nonspecifically allow spleen cells to respond to minor H antigens in vitro. Using minor H congenic mice (congenic for H-Y and/or H-7) I have also tried, and failed, to demonstrate a carrier effect in priming. Female mice primed to H-Y were challenged in culture with cells bearing H-Y and H-7 antigens in the hope that a helper response to H-Y would augment a CTL response to H-7. This did not happen, however. Such primed and boosted cells gave a strong secondary CTL response to H-Y but none to H-7. It is concluded that in order to prime for a detectable in vitro response to minor antigens it is necessary to expose the CTL precursors to antigen in vivo. This either expands the size of the pool of precursors by cell division or changes them in some qualitative way.     

Graft-versus-host disease in experimental allogeneic bone marrow transplantation

Considerable progress has been made in defining the relative contributions of CD4+ and CD8+ cells to GVHD. Studies in mice have shown that, in isolation, each T cell subset is able to induce lethal GVHD in irradiated hosts. For hosts differing at the MHC (H-2), CD4+ cells cause GVHD directed to H-2 class II antigens whereas CD8+ cells produce GVHD to H-2 class I antigens. With H-2-matched hosts expressing multiple minor H antigens, induction of lethal GVHD is largely under the control of CD8+ cells. Which particular minor H antigens provide the targets for GVHD in mice is still unclear. Clarifying this question is complicated by the finding that the target antigens for GVHD do not necessarily correlate with the targets for cytotoxicity measured in vitro; moreover, immunodominance occurs when T cells are exposed to multiple minor H antigens in vivo. In terms of clinical application, there is a need to devise animal models for improving the success of HLA-matched bone marrow transplantation. Selectively depleting the marrow inoculum of CD8+ cells and preimmunizing the donor against viral pathogens are two procedures which are currently under study.     

Modulation of natural cytotoxicity by alloantibodies: III. Augmentation of natural killer activity by alloantisera directed against K,D, and I regions of the murine H-2 complex

Natural killer activity of mouse spleen cells toward a human myeloid leukemia cell line, K562, can be enhanced by alloantisera directed against individual antigens in the H-2 region. By using a panel of 13 antisera (8 directed against antigens in the K and D regions and 5 directed against antigens in the I region) and four strains of mice (C57BL/6J, CBA, DBA/2, and A/J) it was found that certain antisera would stimulate target cell lysis by spleen cells only if the antisera had specificity for antigens which were a part of the haplotype represented on the spleen NK effector cells. Anti Ia antisera could stimulate the anti K562 NK activity of nude mouse spleen cells which lack mature T cells. Depletion of B cells and macrophages from nude spleen cells, by passing through a nylon-wool column also did not abolish the effect of anti-Ia antiserum. It appears likely therefore that the anti-Ia antibodies exert this effect directly on NK cells and that Ia antigens may be expressed on NK cells. Since the antisera directed against different antigens in H-2 complex irrespective of subregion specificity (K, D, or I) stimulated the NK activity of mouse spleen cells, the phenomenon offered an interesting method for testing the presence of a given alloantigen on mouse spleen cells. Log-dose response curves for the augmentation of lysis induced by appropriate alloantisera were linear over a dilution range of 1:320 to 1:5120. By using the dose-response curves, potency ratios of two preparations of antisera (directed against antigen 33 of the K region) could be successfully determined. Besides the K562 cell line, many human lymphoblastoid cell lines could also be used as target cells in this assay system.     

Spleen cells from animals neonatally tolerant to H-2Kk antigens recognize trinitrophenyl-modified H-2Kk spleen cells

A.TL mice injected with (A.AL × A.TL)F₁ cells within 24 hours after birth were rendered tolerant to H-2K^k antigens, as evidenced by acceptance of A.TL skin grafts. When spleen cells from these tolerant animals were cocultured with A.AL stimulator cells, no cytotoxic effector cells were generated in a cell-mediated lympholysis assay. However, when the A.AL stimulator cells were derivatized with trinitrophenol, effector cells that displayed a cytotoxic effect against trinitrophenyl-modified H-2K^k target cells were generated. These data indicate that animals tolerant to H-2 determinants but chimeric to only a minor extent possess cytotoxic precursor cells in sufficient frequency to mount a primary in vitro response against trinitrophenol in the context of an allogeneicH-2K region.     

Immunogenetic analysis ofH-2 mutations

A.BY, B10.LPa, and B10.129(5M) mice were presensitized in vivo against B10.A(5R) cells and then restimulated in vitro by the same cells in the standard CML assay. The effector cells thus generated lysed not only B10.A(5R), but also C57BL/6 targets, indicating that, in addition to anti-H-2D_d response [measured on the B10.A(5R) targets], response to minor histocompatibility (H) antigens (measured on the C57BL/6 targets) also occurred. The latter response was directed against multiple minor H antigens in the case of the A.BY effectors, and against H-1 and H-3 antigens in the case of B10.129(5M) and B10.LPa effectors, respectively. The sensitization against minor H antigens occurred in the context of H-2K^b H-2D^d antigens, but by testing the response on C57BL/6 targets, only cells reacting with minor H antigens in the context of H-2K^b were assayed. The same effector cells were then tested against H-2^b mutant strains, in which theH-2K ^b allele was replaced by a mutant one. All three effector types [A.BY, B10.LPa, and B10.129(5M)] behaved in a similar way: they all reacted with theH-2 ^bg1 mutant to the same degree as withH-2 ^b, they did not react at all or reacted only weakly with theH-2 ^bd andH-2 ^bh mutants, and they reacted moderately or strongly with theH-2 ^ba mutant. The degree of crossreactivity with the mutants reflects, with one exception, the degree of relatedness of these mutants toH-2 ^b, as established by other methods. The one exception is theH-2 ^ba mutant, which is the most unrelated toH-2 ^b, and yet it crossreacted strongly. Further testing, however, suggested that in this instance the crossreactivity was probably directed against H-2 antigens: the anti-H-2D^d effectors apparently crossreacted with the H-2K^ba antigens. This finding is an example of cell-mediated crossreactivity between the products of two differentH-2 genes (H-2K andH-2D). It is also an example of anH-2 mutation generating an antigenic determinant known to be present in another strain.     

Detection of shared H-2Kk and H-2Dk antigens that function as self determinants for cell-mediated lympholysis to trinitrophenyl-self

Spleen cells from C3H/He mice immunized in vivo to trinitrophenyl (TNP)-self were sensitized in vitro to TNP-self. These spleen cells displayed strong lysis on TNP-modified H-2D end-matched (Kd-Dk) targets as well as enhanced cytotoxicity against H-2 matched (Kk-Dk) or H-2K end-matched (Kk-Dd) target cells. Cold target-blocking studies showed that the lysis of TNP-Kd-Dk targets could be blocked by the addition of TNP-modified Kk-Dk, Kk-Dd Kk-Db, or Kd-Dk, but not by TNP-modified Kd-Dd, Kb-Db and Kq-Kq spleen cells. These results demonstrate that the lysis of TNP-Kd-Dk targets is not due to cross-reactive clones against TNP-Kd-Dd, Kb-Db or Kq-Dq antigens. Inhibition of the TNP-Kd-Dk target lysis by TNP-Kk-matched (Kk-Dd or Kk-Db) as well as TNP-Dk-matched (Kd-Dk) blockers also reveals that this target is lysed by clones directed against shared antigens between Kk-TNP and Dk-TNP, indicating that no cytotoxic response restricted for Dk-TNP only could be detected even after in vivo priming.     

Immune recognition by cytotoxic T lymphocytes of minor histocompatibility antigens expressed on a murine colon carcinoma line

We have characterized in vivo and in vitro responses of mice to the BALB/c-derived carcinoma, C26. BALB/c mice were highly susceptible, in a dose-dependent fashion, to local tumor development following subcutaneous injection of C26. Other strains of mice, including allogeneic strains and major histocompatibility complex compatible strains of different minor histocompatibility (H) backgrounds, were resistant to C26-induced tumors. The basis for resistance of mice to C26 was studied using an in vitro-derived C26 line as target cells in microcytotoxicity assays, and as a source of antigen for in vivo priming. An H-2d-specific alloreactive cytotoxic T lymphocyte (CTL) line was isolated from C57BL/6 mice primed with C26, demonstrating the expression, and immune recognition, of MHC class I antigens on C26. C26 also expressed minor H antigens of BALB background as demonstrated by the ability of CTL specific for BALB minor H antigens to selectively lyse C26. Conversely, minor H antigens on C26 were immunogenic across a minor H barrier as demonstrated by the ability to raise anti-minor H CTL to C26 from minor H disparate strains. Collectively, those experiments indicate that C26 may be useful for immunologic and biochemical studies of murine minor H antigens, and for in vivo and in vitro studies of local immunity.     

Differential expression of the repertoire in in vitro and in vivo responses to minor alloantigens

The response to multiple minor alloantigens in the secondary mixed lymphocyte culture (MLC) between mouse strains that are identical at the major histocompatibility complex (MHC) generally yields effector cytotoxic T lymphocytes (CTL) which show cross-reactive killing of most or all third-party mouse strains which also share MHC haplotypes. We have investigated the clonal diversity of CTL responses in vivo versus in vitro by examination of such cross-reactions, using CTL effector cells derived from a primary response, an in vivo secondary response, and an in vitro secondary MLC. CTL from these three responses were assayed on a panel of H-2' targets. Restimulation of antigen-primed spleen cells in vitro yielded CTL which were strongly cross-reactive on all targets, whereas the in vivo responses were much less so. We conclude that the set of clones which become cytotoxic effectors in vivo is much less diverse than the set which is primed on a first encounter with antigen and that powerful constraints must therefore operate on the specificity of in vivo responses to non-MHC antigens.     

The role of HLA antigens in the control of the cytotoxic T-cell response to Epstein-Barr virus: a family study

Epstein-Barr (EB) virus-specific, HLA-restricted cytotoxic T-cell populations have been generated in vitro from each member of a family by cocultivating peripheral blood mononuclear cells with autologous EB virus-transformed B cells, the resulting effector cells being expanded as interleukin 2-dependent T-cell lines. The cytotoxicity of each of these effector populations was tested on a large panel of EB virus-transformed target cells of known HLA type, so that the particular HLA antigens which acted as restricting elements for each cytotoxic population could be identified. There was a consistent pattern within the family of preference for certain HLA class I antigens as restricting elements of the virus-specific T-cell response. Extensive functional analysis showed that, in addition to the virus-specific lysis, each effector population mediated a cross-reactive lysis against target cells prepared from certain HLA-mismatched individuals. This cross-reactivity appeared to be directed against HLA class I alloantigens and occurred irrespective of the EB virus genome status of the target cells. Effector T-cell lines derived from different family members but with virus-specific lysis predominantly restricted through the same HLA antigen showed similar patterns of concomitant allo-cross-reactivity. This suggests that antigenic mimicry of virally altered self by alloantigens is a genuine phenomenon which may be important in channelling the human cytotoxic T-cell response to a virus through preferred self-HLA determinants.     

Suppressor T cell recognition of major and minor histocompatibility alloantigens: selected suppression of MHC-directed responses by minor alloantigen Ts

The induction of suppression by i.v. administered alloantigens in the murine host was analyzed as a model of the possible effects of blood transfusion on transplant survival. The results indicated that suppressor T cells (Ts) specific for minor histocompatibility alloantigens could be readily induced by the i.v. presentation of minor alloantigen-disparate spleen cells. In contrast, similar priming with cells differing solely at the H-2 major histocompatibility complex stimulated only positive T cell immunity, with no evidence of suppression. The induction of H-2 directed Ts activity could be accomplished only by i.v. priming with major plus minor incompatible donor cells, suggesting that suppressor cell recognition of minor alloantigens may have facilitated the generation of Ts against H-2-encoded major transplantation antigens. A role for minor histocompatibility antigens in the regulation of H-2-specific immunity at the effector level was also indicated. Ts induced by i.v. pretreatment with minor antigen-disparate donor cells not only suppressed the delayed-type hypersensitivity (DTH) response to the relevant minor alloantigens, but also inhibited DTH against unrelated H-2 alloantigens introduced during subsequent intradermal immunization. Suppression of H-2-directed T cell reactivity was specific in that the presence of the Ts-inducing minor alloantigens was also required and occurred only when the minor and unrelated major alloantigens were presented within the same inoculum, if not on the same cell surface. The capacity of Lyt-2+Ts or Ts-derived suppressive factors specific for one set of cell surface molecules to modulate responses to an unrelated group of surface antigens does not appear to represent a general phenomenon, because similar suppression of immunity to unrelated tumor-specific transplantation antigens by minor-specific Ts was not observed. These results are discussed with respect to the possible mechanism of H-2-directed suppression and the role of the I region in Ts recognition of antigen.     

Anti-recipient cytotoxic T lymphocyte precursors are present in the spleens of mice with acute graft versus host disease due to minor histocompatibility antigens

A model for bone marrow transplantation across minor histocompatibility barriers was developed by using mouse strains that were H-2 identical and mutually non-reactive in MLC. Acute graft-vs-host disease was induced only when donor lymphoid cells were included in the marrow inoculum, in both C57BL/6 recipients of LP cells and BALB/c recipients of B10.D2/nSN cells. GVHD was prevented by treating the lymphoid cells with anti-Thy 1.2 and C before transplantation. Spleen cells from mice with acute GVHD were not directly cytotoxic to recipient strain target cells. However, when spleen cells from mice with GVHD were boosted in vitro to recipient strain stimulator cells they generated a specific anti-recipient cytotoxic response. Spleen cells from mice without GVHD did not generate a cytotoxic response in vitro. The cytotoxic effector cells and their precursors were shown to be T lymphocytes. This model and the in vitro method described may be useful in further studies of the immunobiology of GVHD due to minor histocompatibility antigens and of transplantation tolerance.     

Generation of cytotoxic lymphocytes in mixed lymphocyte reactions II. Importance of private and publicH-2 alloantigens on the expression of cytotoxicity

MLC were established to test for the generation of specific cytotoxic effector cells in CML. The target cell used to assay for CML in the five combinations tested was of a differentH-2 haplotype from the stimulating cell population. Cytotoxicity was observed against this target only when it shared private alloantigens (antigens that are specific for theH-2D andH-2K region of differentH-2 haplotypes) with the stimulating cell population. Very weak or no Cytotoxicity was found when such alloantigens were not shared, although cross-reactive publicH-2 specificities were. These findings indicate that T cells display a cytotoxic potential against privateH-2 antigens in a primary response in vitro and are not capable of responding to publicH-2 specificities to the same level.BSS balanced salt solution - CML cell-mediated lympholysis - GPC guinea pig complement - ¹²⁵IUdR ¹²⁵I-iodo-deoxyuridine - MLC mixed lymphocyte culture - SE standard error     

H2Kk can influence whether cytotoxic T lymphocytes recognize trinitrophenyl in association with H2Dk unique or H-2Kk and H-2Dk shared self determinants

The present study investigates the effect of trinitrophenyl- (TNP) modified H-2Kk (TNP-Kk) antigens on the generation of anti-TNP-Dk restricted cytotoxic T lymphocyte (CTL) responses. C3H.OH mice were primed to TNP-self by skin-painting with trinitrochlorobenzene, and spleen cells from these primed mice were subsequently stimulated in vitro with TNP-self. The effector cells generated exhibited appreciable lysis of TNP-modified C3H.OH blast target cells. Cold target inhibition studies demonstrated the generation of two effector cell populations: one that recognizes TNP in association with unique Dk self determinants, and one that recognizes TNP in association with self determinants shared between TNP-Kk and TNP-Dk. This was in contrast to primed C3H/He spleen cells, which did not generate CTL that recognized TNP in association with unique Dk self determinants. When spleen cells from (C3H/He x C3H.OH)F1 mice primed to TNP were stimulated in vitro with TNP-C3H.OH cells, unique Dk self determinants were recognized in association with TNP. However, in vitro stimulation of the same F1 responding cells with TNP-C3H/He or TNP-F1 cells failed to elicit CTL that utilized these Dk-unique self determinants. The findings of this study demonstrate that unique or shared H-2Dk determinants can be differentially utilized by CTL populations, depending on the H-2 alleles expressed by the stimulator cells.     

Specificity of H-2-linked Ir gene control in mice: demonstration of T helper cells recognizing branched synthetic polypeptides in low responder mice

This report provides evidence for the presence of T helper cells capable of recognizing the polypeptide antigens T6-A--L and (H,G)-A--L in low responder mice of H-2k and H-2b haplotypes, respectively. Mice were primed in vivo with the T6-A--L-avidin-(H,G)-A--L complex or, in the case of T6-A--L in H-2k mice, with the cross-reactive and permissive antigen T6-S--L. T helper cells cooperating with DNP-primed B cells could be rechallenged in vitro with the DNP-conjugates of T6--A--L or (H,G)-A--L, although the cells were of low responder type with respect to these antigens. This implies that T cell-macrophage interaction required for restimulation is apparently not defective in these low responders. The implications of these results for the concept of Ir gene control are discussed.     

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.     

Synergism of T lymphocyte subsets in the response to Mls-locus coded antigens during graft-versus-host reaction

After transplantation of lymphoid cells into lethally irradiated (semi)allogeneic mice specific anti-host directed effector T cells are generated. This can be demonstrated using a delayed type hypersensitivity (DTH) assay. In H-2 compatible combinations, Mls-locus antigens, but no other minor histocompatibility antigens, can induce the generation of such effector T cells. This paper shows that maximal anti-host DTH responses are obtained when the lymphoid cells transplanted constitute of a mixture of long-lived, recirculating T2 cells and short-lived, sessile T1 cells. It was demonstrated that anti-Mls locus-directed DTH effector T cells are the progeny of T2 cells, and that T1 cells amplify this response. The latter, however, are by themselves incapable of displaying anti-Mls DTH reactivity. The T1 cells were found to be of the Lyt-1+2+ phenotype, and the T2 cells of the Lyt-1+2- phenotype. The same Lyt phenotypes were found for T1 and T2 cells synergizing in the GvH reaction against H-2 alloantigens.