In vitro analysis of allogeneic lymphocyte interaction. III. Generation of a helper allogeneic effect factor (AEF) across an I-J subregion disparity.

Allogeneic effect factors (AEF) were produced across an I-J subregion incompatibility. The helper activity of these AEFs is H-2 restricted since they help B cells only of the stimulator haplotype and of other haplotypes that carry the same I-J subregion gene(s) as the stimulator haplotype. Immunoadsorption studies demonstrate that they consist of I-J determinants derived initially from the GVHR host and MLR stimulator cells and not the GVHR donor and MLR responder cells used to generate AEF. It is postulated that the genetic restriction of AEF helper activity is mediated in part by the ability of the GVHR activated donor T cells to acquire, in vivo, recipient T cell and/or macrophage derived I-J determinants. Cellular adsorption studies indicate that AEF helper activity may be adsorbed by B cells, but neither T cells nor macrophages, of the stimulator haplotype. The results suggest that an I-J-positive AEF interacts with an I-J subregion controlled complementary recognition structure on a target B cell and, after antigenic stimulation, activates that B cell to IgG antibody synthesis.     

Alloreactive lymphocytes from T cell receptor (beta-chain) transgenic mice do not mediate a graft-versus-host reaction.

The injection of mature T cells into a tolerant or immunocompromised allogeneic host animal produces a graft versus host response (GVHR) that can result in splenomegaly, immunosuppression and death of the host animal. We demonstrate here that lymphocytes from T cell receptor beta-chain (TCR-beta) transgenic mice, in which the expression of the transgene inhibits endogenous beta- and gamma-gene rearrangements and thus causes abnormal T cell development, are unable to mediate a GVHR. The GVHR was measured after the injection of lymphocytes from transgenic mice into normal F1 mice and also after transplantation of bone marrow and lymphocytes from transgenic mice into lethally irradiated F1 recipients. In both systems, cells from transgenic mice failed to produce a significant GVHR. Cells from the transgenic mice were able to recognize the foreign histocompatibility Ag of the host in vitro and in vivo although the transgenic mice rejected skin grafts more slowly than controls. Thus, lymphocytes from transgenic mice were unable to produce a GVHR despite the presence of alloreactive T cells. These results suggest that lymphocytes from TCR-beta transgenic mice fail to mediate a GVHR either because lymphocytes with a single transgenic TCR-beta chain have a limited ability to recognize allogeneic cells in vivo or because the transgenic mice lack lymphocyte subsets that are important for the mediation of a GVHR.     

Activation or suppression of bactericidal activity of macrophages during a graft-versus-host reaction against I-A and I-J-region differences, respectively

Systemic graft-versus-host reactions (GVHR) were induced in F1 heterozygous mice by injecting 10(8) parental lymphocytes. The Anti-Thy 1.2-sensitive, T-cell mediated activation of macrophages was assessed by their increased capacity to destroy a facultative intracellular bacterium Listeria monocytogenes. The difference in MHC regions causing a GVHR that induced high levels of macrophage activation mapped to I-A. In contrast, differences at K or D, in any of the other H-2 subregions or in the non-H-2 background, including Mls alone or in combination, did not induce a GVHR leading to macrophage activation, unless these differences were combined with a difference at I-A. The numbers of parental cells needed to activate macrophages via a GVHR caused by I-A vs. non-I-A differences, varied at least 30- to 100-fold. When parental cells were injected into F1 offspring of parents differing at I-J, growth of Listeria was enhanced significantly; this negative effect on macrophages was not seen when parental combinations differing at I-A alone were compared with those differing at I-A plus I-J or I-J plus other H-2 regions.     

Role of L3T4+ and Lyt-2+ donor cells in graft-versus-host immune deficiency induced across a class I, class II, or whole H-2 difference

The i.v. injection of parental T cells into F1 hybrid mice can result in a graft-vs-host (GVH)-induced immune deficiency that is Ag nonspecific and of long duration. The effect of the GVH reaction (GVHR) on the host's immune system depends on the class of F1 MHC Ag recognized by the donor cells. To determine the role of different subsets of donor-derived T cells in the induction of GVHR, donor spleen cells were negatively selected by anti-T cell mAb and C, and the cells were injected into F1 mice that differed from the donor by both class I and II MHC Ag or by class I or class II MHC only. The induction of GVHR across class I + II differences was found to require both L3T4+ and Lyt-2+ parental cells. Induction of GVHR across a class II difference required only L3T4+ parental T cells in the combination tested [B6-into-(B6 x bm12)F1]. In contrast, B6 Lyt-2+ cells were sufficient to induce GVHR across a class I difference in (B6 x bm1)F1 recipients. In addition, a direct correlation was observed between the cell types required for GVH induction and the parental T cell phenotypes detected in the spleens of the GVH mice. The number of parental cells detected in the unirradiated F1 hosts was dependent upon the H-2 differences involved in the GVHR. Induction of a class I + class II GVHR resulted in abrogation of both TNP-self and allogeneic CTL responses. In contrast, induction of a class II GVHR resulted in only a selective loss of TNP-self but not of allogeneic CTL function. Unexpectedly, the induction of a class I GVHR also resulted in the selective loss of the TNP-self CTL response. Thus, these class I and class II examples of GVH both result in the selective abrogation of L3T4+ Th cell function. The data are discussed in terms of respective roles of killer cells and/or suppressor cells in the induction of host immune deficiency by a GVHR, and of the selective deficiency in host Th cell function induced by different classes of GVHR.     

Impaired cellular immunecompetence in infectious mononucleosis as assessed by a local graft-versus-host reaction in rats and restoration of the immunecompetence by trypsin.

Lymphocytes from 11 patients with acute infectious mononucleosis were tested for functional capacity by means of a local graft-versus-host reaction (GVHR) and for T lymphocyte markers by the spontaneous rosette-formation test (E rosette). All of the patients showed an increased percentage (49–75%) and high absolute numbers (2078–8736/mm³) of E rosette-forming cells but no functional activity, i.e., a negative GVHR. Repeated examinations performed in four patients at intervals up to 6 months after the initial test showed a significant drop in the number of E rosette-forming cells although the GVHR remained negative. Trypsinization of lymphocytes performed in nine of the 11 patients resulted in recovery of immunecompetence of the T lymphocytes in five; in contrast, trypsinization of normal control lymphocyte abolished their ability to mount a normal GVHR. In view of the number of cases in which infectious mononucleosis has been followed by lymphoproliferative diseases, the importance of long-term follow-up in patients who have undergone an episode of infectious mononucleosis is stressed.     

Differences in thymus dependency among the alloreactive T-cell subpopulations in their development

Effects of thymectomy at various times after birth (Tx-1, Tx-3, Tx-7, Tx-14) on mixed lymphocyte reaction (MLR), cell-mediated cytotoxicity (CMC), and graft-versus-host reaction (GVHR) were examined by experiments with spleen cells obtained at 8 weeks of age. All of MLR, CMC, and GVHR were detected in spleen cells of Tx-14 mice. However, the ability of spleen cells to induce GVHR was abolished by thymectomy at 7 days after birth. On the other hand, MLR and CMC were not affected in such mice. In Tx-1 or Tx-3 mice, only MLR was detected in spleen cells. These results suggest that thymus dependency of T cells responsible for MLR are lower in their maturation than those for CMC and that thymus dependency of T cells responsible for GVHR are the highest among these T-cell subpopulations.     

Functional state of the thyroid gland during systemic graft vs host reaction

Triiodothyronine (T3), thyroxine (T4) and thyroid stimulating hormone (TSH) serum content was measured in mice during systemic "graft-versus-host" reaction (GVHR), using radioimmunoassay. It was demonstrated that on the 3rd day after GVHR induction the levels of these hormones did not differ from the control values. T3 and T4 concentrations and 125I absorption by thyroid gland diminished by day 10. At the same time TSH level remained unchanged. On day 24 after GVHR induction T3 and T4 content was significantly reduced, although TSH concentration exceeded the control value. 125I absorption was enhanced as compared to the value observed on day 10. The data obtained show the vigorous inhibition of thyroid gland function during systemic GVHR.     

GVHR elicited by products of class I or class II loci of the MHC: analysis of the response of mouse T lymphocytes to products of class I and class II loci of the MHC in correlation with GVHR-induced mortality, medullary aplasia, and enteropathy

A lethal graft-vs-host reaction (GVHR) was elicited by the injection into irradiated (700 rad) mice, reconstituted with T-depleted bone marrow cells (BM), of T lymphocytes incompatible for different loci of the major histocompatibility complex (MHC). The number of T cells needed to kill more than 50% of the recipients by day 40 was about 10(6) for GVHR elicited across the product of the K, D, or E locus, but about 10(5)--10--fold less-when the A locus was involved. The mortality was associated with a medullary aplasia in all strain combinations, but enteropathy was observed only in GVHR elicited by the products of class II, and not class I, loci. Mortality and medullary aplasia were diminished or absent in recipients reconstituted with BM cells from T cell donors instead of cells of the host genotype, which suggests a direct (cytolytic) T-hematopoietic cell interaction. Lymphoproliferation was evident within the host spleen and lymph node 5 days after injection of T lymphocytes incompatible for class II but not class I loci. Spleens from mice suffering from a lethal GVHR were examined by culture in limiting dilution to evaluate the frequency of anti-host T cells and to derive anti-host T cell clones and lines, whose properties were explored. In the GVHR elicited across the A or E region of the MHC, examined between days 7 and 19, a high frequency (10(-2] of anti-host cells was observed. The polyclonal cell lines isolated (16) all displayed MLR responsiveness, antigen-driven IL 2 production, and cytolysis for LPS blasts of the host genotype. However, among 13 clones isolated, two categories were observed: Lyt-2-, which were MLR responders and IL 2 producers (four of 13), and Lyt-2+, which were cytolytic but neither MLR responders nor IL 2 producers (nine of 13). In the GVHR elicited by the K or D region, examined between days 7 and 90, the frequency of anti-host cells was low (10(3) to 10(4], with a tendency to decrease during the progression of the disease. The lines (11) or clones (26) isolated from different mice were all Lyt-2+ and strongly cytolytic but proliferated poorly and produced no IL 2 in MLR. These findings suggest that the Lyt-2+ lymphocytes, recognizing the products of the class I loci, function in vivo without proliferation and without requiring helper T cells. Cell lines specific for class I or class II loci of the MHC produced interferon and colony-stimulating factors.     

Mlsa generated suppressor cells. I. Suppression is mediated by double-negative (CD3+CD5+CD4-CD8-) alpha/beta T cell receptor-bearing cells.

Grafting of cells from B10.D2 (H-2d) donors into H-2 compatible lethally irradiated (DBA/2 x B10.D2)F1 hosts results in a severe graft-vs-host reaction (GVHR), developed against DBA/2 non-H-2 Ag, with only 0 to 10% of animals surviving. This GVHR mortality rate is dramatically reduced (90 to 100% of animals survive) by donor preimmunization against Mlsa determinants. The protection against GVHR correlates with a decreased B10.D2 anti-DBA/2 proliferative response in vitro. Both in vivo and in vitro phenomena are associated with activation of CD5+ suppressor T cells in the spleens of immunized mice. The present work was designed to study the origin of these suppressor cells and to further characterize their phenotype. The results show that significant suppression is not inducible in "B" mice. In contrast, in mice that were only thymectomized or else pretreated in vivo with anti-CD4 or anti-CD8 mAb, the suppressor cells are activated as efficiently as in normal mice. The suppression of GVHR mortality and proliferative responses in vitro is lost after depletion from preimmunized splenocytes of CD5+ T cells and remains unaltered after depletion of CD4+ or CD8+ T cells or both. Depletion of asialo GM1+ cells removes all NK activity, whereas the suppression is decreased only slightly. FACS analysis showed that double-negative (DN) cells from normal and immunized mice contain both CD3+ and CD3- cells; the vast majority of the CD3+ DN T cells express the alpha/beta T cell receptor. Suppression of GVHR and of proliferative responses in vitro are abrogated after elimination of CD3+ cells. These results suggest that Mlsa generated suppressor cells: 1) are derived from post-thymic long-lived T cell precursors; 2) are low asialo GM-1+ but do not exhibit NK activity; 3) belong to a subset of peripheral CD5+ DN T cells bearing a CD3-associated alpha/beta-heterodimer.     

Mls-1a-induced peripheral tolerance to host minor histocompatibility antigens in radiation bone marrow chimeras. Modification of T cell repertoire associated with active suppression and permanent presentation of host antigens.

Minor histocompatibility Ag (mHAg) can be responsible for the development of graft vs host reaction (GVHR) after bone marrow transplantation. In a mouse model, B10.D2 donor immunization against Mls-1a prevents lethal GVHR developed by CD4+ T cells against DBA mHAg in irradiated (DBA/2 x B10.D2)F1 hosts. Such F1 hosts become 100% chimeric and show long term survival (LS mice). The cellular mechanisms underlying the tolerance in LS mice was investigated. It was found that a state of tolerance can be induced in thymectomized F1 hosts. Although spleen cells from LS mice are able to initiate lethal GVHR in third-party H-2k-incompatible hosts, no GVHR is observed in secondary hosts incompatible for specific DBA/2 mHAg. Mixed lymphocyte experiments in vitro confirm that T cells from LS mice are unresponsive toward specific DBA/2 mHAg, although they are able to proliferate in response to H-2 or Mls-1a Ag. The responsiveness to Mls-1a correlates with the presence of V beta 6+ cells in LS mice, probably derived from mature T cells present in the donor inoculum. The tolerance in LS mice is not due to the lack of DBA/2 mHAg presentation; instead, permanent presentation of Ag (Ag I and Ag II) previously described as being responsible for lethal GVHR is consistently observed. A significant protection against GVHR is obtained by transferring normal B10.D2 cells together with spleen cells from LS mice, clearly indicating the contribution of active suppression in the state of tolerance; this is further confirmed by in vitro results obtained in limiting dilution assays. It is concluded that tolerance in chimeric LS mice 1) is due to a peripheral (thymus-independent) mechanism; 2) is specific for mHAg; 3) correlates with unresponsiveness of the repertoire to host mHAg, without alteration of the repertoire for H-2 and Mls-1a Ag; and 4) is associated with an active suppression and with a permanent presentation of at least two mHAg responsible for GVHR mortality.     

The Lyb-3+5+ subset of B cells is not required for lupus-like autoantibody formation caused by graft-vs-host reaction

We asked the question whether or not the Lyb-3+5+ B cell subset, which is lacking in CBA/N immune defective mice, is required for the lupus-like autoantibody formation caused by graft-vs-host reaction (GVHR). (CBA/N X DBA/2)F1 male defective mice injected with DBA/2 T cells produced IgG autoantibodies to the same extent as did nondefective F1 mice suffering from GVHR. Although a very small number of DBA/2 B cells might have contaminated the T cell inocula, it was shown that these were B cells of the defective F1 mice that produced autoantibodies during the GVHR. This was demonstrated by detecting autoantibodies carrying an immunoglobulin allotype of the F1 recipient. Furthermore, the defective F1 male mice injected with CBA/N lymphoid cells, which were lacking Lyb-3+5+ B cells, also produced autoantibodies. Isotype analysis of antinuclear antibodies revealed that some of them belonged to IgG3 isotype. It was concluded that the ontogenically late-appearing B cell subset is not required for GVH autoimmunity.     

Activation or suppression of bactericidal activity of macrophages during a graft-versus-host reaction againstI-A andI-J-region differences,respectively

Systemic graft-versus-host reactions (GVHR) were induced in F₁ heterozygous mice by injecting 10⁸ parental lymphocytes. The Anti-Thy 1.2-sensitive, T-cell mediated activation of macrophages was assessed by their increased capacity to destroy a facultative intracellular bacteriumListeria monocytogenes. The difference inMHC regions causing a GVHR that induced high levels of macrophage activation mapped toI-A. In contrast, differences atK orD, in any of the otherH-2 subregions or in the non-H-2 background, includingMls alone or in combination, did not induce a GVHR leading to macrophage activation, unless these differences were combined with a difference atI-A. The numbers of parental cells needed to activate macrophages via a GVHR caused byI-A vs. non-I-A differences, varied at least 30- to 100-fold. When parental cells were injected into F₁ offspring of parents differing atI-J, growth ofListeria was enhanced significantly; this negative effect on macrophages was not seen when parental combinations differing atI-A alone were compared with those differing atI-A plusI-J orI-J plus otherH-2 regions.     

Frequency analysis of lymphokine-secreting CD4+ and CD8+ T cells activated in a graft-versus-host reaction

Lymphokine secretion by in vivo-activated T cells was analyzed at the population and single-cell levels in lymphocytes from mice undergoing an acute allogeneic graft-vs-host reaction (GVHR). Three observations were made. First, constitutive lymphokine production by these cells was very low but could be dramatically up-regulated by TCR ligation. Thus, even when harvested at the peak of the GVHR, fewer than 0.1% of lymphocytes secreted detectable granulocyte-macrophage (GM)-CSF, IFN-gamma, or IL-3 in the first 24 h in vitro, and average production of these lymphokines in bulk cultures was less than 10(-5) U/cell. However, when cultured for 24 h with anti-CD3 antibody under conditions which activated less than 0.1% of normal cells, about 30% of GVHR T cells secreted GM-CSF, IFN-gamma, and/or IL-3, and average production levels were increased by 10(3)- to 10(4)-fold. Together with evidence that host alloantigen-induced lymphokine secretion was 10 to 100 times lower than the anti-CD3 response, these data suggest that physiologic lymphokine synthesis by most T cells is low (less than 10(-18) mol of IL-3 per cell) but can be raised above the threshold of detection by TCR cross-linking. Second, individual GVHR lymphocytes varied markedly in their total and relative production of different lymphokines in response to anti-CD3 stimulation, with some cells secreting IL-3 alone, some secreting IL-3 accompanied by other lymphokines (GM-CSF and/or IFN-gamma), and some secreting other lymphokines without detectable IL-3. Finally, both CD4+ and CD8+ T cells from GVHR mice responded to anti-CD3 antibody by secreting IL-3 and other lymphokines: purified CD4+ cells contained an average of 16% and CD8+ cells an average of 10% anti-CD3-inducible lymphokine-secreting cells. By contrast, only 2 to 3% of cells of either subset formed clones in cultures with host allogeneic cells and IL-2, suggesting that clonogenic alloreactive cells were a minority of the T cells activated in the GVHR.     

Transplantation immunology of the anterior chamber of the eye. I. An intra-ocular graft-vs-host reaction (immunogenic anterior uveitis).

A graft-vs-host reaction (GVHR) expressed as an anterior uveitis was elicited within the anterior chambers of the eyes of F1 hybrid rats by the inoculation of suspensions of allogeneic, parental lymph node cells. This response resembled local GVHRs induced in other sites, except for the failure of refractoriness to appear following resolution of the acute phase. Because lymphoid cells within the anterior chamber have been shown to leave and make an impact on the systemic immunologic apparatus of the recipient, rather than remain isolated within the eye, it was suggested that the vascular route by which these cells disseminate is an important determinant of whether refractoriness will ensue from a local GVHR.     

Depletion of CD8+ cells exacerbates organ-specific autoimmune diseases induced by CD4+ T cells in semiallogeneic hosts with MHC class II disparity

Autoimmune diseases are known to be induced in some donor-recipient combinations of mice undergoing the graft-vs-host reaction (GVHR). In this paper, we report on the development of primary biliary cirrhosis (PBC)-like hepatic lesions and also on pancreatic insulitis in (B6 x bm12)F1 mice injected with B6 CD4+ T cells. At the sites of these lesions, cellular infiltration around ductal structure was observed. Immunohistochemical studies revealed that both CD4+ and CD8+ T cells were present in the lesions of the liver and pancreas. To clarify the role of the CD8+ T cells, which were probably of host origin, we used a mAb against the Lyt-2 molecule. Both the PBC-like hepatic lesions and pancreatic insulitis were exacerbated by eliminating CD8+ T cells from mice with MHC class II GVHR. Also, autoantibodies against the pyruvate dehydrogenase-E2 component, which has been recently found to contain an immunodominant site (autoepitope) for B cell reactivity in patients with PBC, were detected in the sera of these mice by ELISA and their presence was confirmed by immunoblotting procedures. Our findings suggest that similar mechanisms as in GVHR caused by MHC class II disparity are active in the development of PBC. It should also be noted that, in addition to the hepatic lesions, insulitis closely resembling that seen in the nonobese diabetic mouse was induced in our experimental system. The results suggest that our model provides a unique opportunity to study organ-specific autoimmune diseases. Because the effector in our experimental system was defined to be CD4+ T cells responding to Iabm12 Ag, our findings support the hypothesis that an excessive immune response directed against Ia Ag can produce autoimmune disease.     

Early intestinal Th1 inflammation and mucosal T cell recruitment during acute graft-versus-host reaction

Little is understood about the earliest cytokine responses and the role(s) of donor CD4 T cells in the intestine during the induced graft-vs-host reaction (GVHR). We investigated the activation and mucosal homing phenotype of the donor CD4 cells and the kinetics of cytokine responses within the intestine and associated lymphoid tissues during early GVHR. Significant frequencies of donor CD4 cells accumulated within recipient Peyer's patches (PP), mesenteric lymph nodes (MLN), lamina propria (LP), and spleen (SP), during the first 9 days of GVHR. Many donor CD4 cells in SP, MLN, and LP expressed CD44 and also expressed de novo the mucosal homing integrin alpha(4)beta(7) (LPAM-1). A large IFN-gamma response occurred by day 3 in cells from PP and MLN, but much later (day 9) in SP and LP cells. IL-10 production by SP and MLN cells was elevated initially but declined substantially by day 9. IL-4 production by SP, MLN, and PP cells was low on day 3 and showed gradual decline in LP by day 9. IL-5 production by LP cells gradually increased in direct contrast to IL-5 production by MLN cells. The MLN CD4 cells showed the most dynamic changes, with high numbers of activated/effector donor CD4 cells and altered cytokine production consistent with a developing Th1 response. The IFN-gamma responses in PP and MLN preceded that of the SP, suggesting an intestinal origin for some Th1 effector cells in GVHR. Donor CD4 T cells apparently acquire the ability to home to the LP during early GVHR.     

Effects of the chromatographic fractions of the pig placental trophoblast on graft-versus-host reaction

The trophoblast has a significant role in regulation of immune reactions at the materno-fetal interface by producing biologically active substances. In our previous studies five fractions with immunomodulatory activities were isolated by gel chromatography from trophoblast of pig placentas. To confirm the immunomodulatory effect of these trophoblast fractions on allogeneic in vivo systems and to obtain more evidence for the relevance of their activity on the maternofetal interface, their effect was studied on graft-versus-host reaction (GVHR). To assess the GVHR, the primary and secondary popliteal lymph nodes assay was used in mice. In the primary GVHR, 100 microg protein of Fraction 2-5, mixed with 5 x 10(6) allogeneic spleen cells (C57BL/6), were injected into one of the foot pads of recipient (BALB/c) mice. The secondary GVHR was induced in F1 (BALB/c x C57BL/6) mice by injection of spleen cells of BALB/c mice intraperitoneally preimmunized with allogeneic cells. The GVHR was measured by the weight of lymph nodes and by the lymphocyte proliferation. Flow cytometric analyses of the cells in the nodes with GVHR and under the influence of Fraction 4 or 5 were performed using monoclonal antibodies. In the primary GVHR, Fraction 4 or 5, injected simultaneously with allogeneic spleen cells, significantly suppressed the lymph nodes reactivity. Fractions 4 and 5 inhibited the ability of the spleen cells of mice intraperitoneally preimmunized with allogeneic cells to induce secondary GVHR in F1 mice. The Fraction 2 and 3 had no effect on GVHR. The results revealed that a group of proteins with Mr 37-7 kDa, isolated from trophoblast of pig placenta, strongly suppressed popliteal lymph node reactivity in the primary and secondary GVHR. The data provide convincing evidence for these fractions in vivo activity, for their effect across the species barrier and suggest the relevance of the same reactions on the materno-fetal interface.     

IgM-mediated, T cell-independent suppression of humoral immunity.

The immunological unreactive state occurring in (T,G)-A-L nonresponder mice after secondary antigen challenge was investigated. Syngeneic IgM anti-(T,G)-A-L antibody-containing plasma, transferred at the time of the time of primary challenge, induced persistent suppression of autologous specific antibody production. Removal of plasma IgM with goat anti-mu antisera removed the ability of the plasma to supress. The induction and maintenance of the suppressed state were not different in thymectomized or sham-thymectomized animals. Primed animals subjected to graft-vs-host reaction (GVHR) at the time of secondary challenge switched over to IgG production. Animals suppressed by passive antibody transfer reacted to GVHR, at the time of secondary challenge, with specific IgM but not IgG antibody production. Transfused normal spleen cells partially abrogated suppression only when (suppressed) hosts had been lethally irradiated. Spleen cells from antigen-plus-antibody suppressed donors, upon transfer to previously normal, syngeneic hosts, were less immunocompetent than spleen cells from untreated donors. These data are consistent with a model of IgM mediated, T cell-independent persistent suppression of humoral immunity.     

Epidermal lesions of the GVHR: evaluation of the role of different MHC and non MHC loci and of the Ly-2+ and L3T4+ T lymphocytes

Irradiated mice (750 rad) were injected with T-depleted bone marrow cells (BMC) and T lymphocytes in various combinations of T/host incompatibility. The epidermis was examined histologically and the incidence of two basic epidermal lesions of graft-vs-host disease (GVHD), the epidermal cell necrosis (ECN) and the lichenoid hyperplastic reaction (LR), were evaluated by a semi-quantitative evaluation. During the acute phase of GVH reaction (GVHR) (days 15 to 25), there was an obvious increase in ECN in reactions elicited by minor loci, whole major histocompatability complex (MHC) differences, or a MHC class I or II difference only. Allogeneic effect without T lymphocyte/epidermis incompatibility did not induce a significant incidence of ECN. Neither depletion of the Ly-2+ nor that of the L3T4+ T lymphocyte subset by treatment with monoclonal antibody (performed in vitro, before injection or also by treatment of the recipient) did prevent the occurrence of ECN, indicating that both T lymphocyte subsets are capable of initiating the epidermal cell damage. The LR was due mainly to the T lymphocytes of the L3T4+, Ly-2- helper phenotype. During chronic GVHR (after 35 days) elicited by either Ly-2+ or L3T4+ lymphocytes, ECN and LR were no longer evident, but the number of epidermal cells and especially the number of replicating cells among the epidermal cells were markedly reduced.