The lpr gene is associated with resistance to engraftment by lymphoid but not erythroid stem cells from normal mice

This study demonstrates cell lineage-specific resistance to engraftment involving lymphocytes but not erythrocytes by the spontaneously autoimmune MRL/lpr mouse strain. In these experiments, MRL/lpr mice were lethally irradiated (1000 R) and reconstituted with normal A-Thy bone marrow stem cells. Periodic analysis from 6 wk to 6 mo posttransplantation demonstrated that the T and B cells of these chimeras were derived from the MRL/lpr host. However, in the same A-Thy----MRL/lpr chimeras, erythrocyte repopulation was completely of A-Thy donor origin. In contrast, control MRL/+ (congenic mice that differ from MRL/lpr at the lpr locus and do not develop accelerated autoimmune disease) recipients were successfully repopulated in both the lymphoid and erythroid compartments by the A-Thy donor cells.     

Analyses of acute graft-versus-host-like reaction in [MRL/lpr----MRL/+] chimeric mice using MRL/lpr-Thy-1. 1 congenic mice.

When MRL/Mp(-)+/+(MRL/+) mice are lethally irradiated and then reconstituted with MRL/Mp-lpr/lpr (MRL/lpr) bone marrow and/or spleen cells, these MRL/+ mice develop "lpr-GVHD" which is similar to acute graft-versus-host disease (GVHD). Using a Thy-1 congenic strain of MRL/lpr mice (MRL/lpr-Thy-1.1), we analyzed T cell subpopulations in the thymus and spleen of MRL/+ mice suffering from lpr-GVHD. lpr-GVHD was induced in MRL/+ mice by transplantation of bone marrow cells (BMC) from MRL/lpr-Thy-1.1 mice; severe lymphocyte depletion associated with fibrosis was observed in the spleens after 7 weeks of bone marrow transplantation (BMT). Thymocytes of the host MRL/+ thymus were replaced with donor-derived cells from the early stage of lpr-GVHD, whereas in the spleen, a small number of host T cells (Thy-1.2+) (4-5%) were retained until the late stage of lpr-GVHD. Donor-type (Thy-1.1+) T cell subsets were not different from those of nontreated MRL/+ mice in the thymus, whereas in the spleen. CD8+ T cells (Thy-1.1+) reached a peak at 5 weeks after BMT, and CD4+ T cells (Thy-1.1+), a peak at 6 weeks. The elimination of T cells from MRL/lpr BMC had no evident effect on the prevention of lpr-GVHD. T cell subpopulations showed a similar pattern to GVHD elicited by MHC differences. Analyses of autoreactive T cells expressing V beta 5 or V beta 11 revealed that autoreactive T cells were deleted from the peripheral lymph nodes. Interestingly, the levels of IgG anti-ssDNA antibodies markedly increased, and both IgM and IgG rheumatoid factors slightly increased 5 to 7 weeks after BMT. These findings are discussed in relation to not only GVHD elicited by MHC differences but also autoimmune diseases.     

B lymphocytes from the autoimmune-prone mouse strain MLR/lpr manifest an intrinsic defect in tetraparental MRL/lpr in equilibrium DBA/2 chimeras

Data are presented showing that MRL/lpr in equilibrium DBA/2 tetraparental (allophenic) chimeras, unlike conventional lpr/lpr----+/lpr bone marrow chimeras, fail to develop graft-vs-host disease; instead they develop full-blown lymphoproliferation and autoantibody formation typical of unmanipulated MRL/lpr mice. The increase in the splenic and especially the lymph node mass is comprised predominantly of MRL/lpr-derived cells and all of the serum IgG2a is MRL/lpr derived. This dominance of MRL/lpr lymphoid activity occurred even in chimeras where greater than 90% of the skin and/or bone marrow cells were of the DBA/2 type. These results demonstrate the failure of the lpr environment to recruit normal B and T cells into the autoimmune process, the inability of normal cells to suppress MRL/lpr disease, and indicate further that the lpr mutation has an intrinsic effect on lymphocytes of both the B and T lineages.     

The effect of thymectomy on lupus-prone mice

The effect of neonatal thymectomy on the induction and/or modification of murine SLE disease was examined in several representative groups of mice with early-life SLE (MRL/Mp-lpr/lpr females, BXSB males, (NZB X W)F1 females, (NZW X BXSB)F1 males and females), late-life SLE (MRL/Mp-+/+ and BXSB females), and normal strains (BALB/c and C57BL/6 females). Our results indicated that thymectomy prevented disease only in the MRL/Mp-lpr/lpr SLE mice, and that this effect diminished as thymectomy was delayed beyond 3 wk post-natally. In the other SLE mice studied, neonatal thymectomy did not modify disease symptoms to any significant degree. Moreover, depletion of mature T cells from donor BXSB male bone marrow did not affect the expression of early-life SLE in thymectomized BXSB female recipients. Neonatal thymectomy did not induce SLE in normal mice. Of note, neonatal thymectomy did not completely deplete the Thy-1.2+ cell population, i.e., 10 to 15% remained in the spleens of the thymectomized mice. This incomplete T cell depletion, together with the previously demonstrated dependence on and hyperresponsiveness of BXSB and (NZB X W)F1 B cells to T helper cell-derived accessory signals, cast doubts on earlier conclusions that B cells from some SLE mice can autonomously proliferate and differentiate to autoantibody-secreting cells. It seems more appropriate to conclude that B cells from the various SLE mice vary in their degree of response to, and production of, T cell-derived helper signals, and thus in their expression of B cell hyperactivity and disease.     

A correlation between conditioning and engraftment in recipients of MHC-mismatched T cell-depleted murine bone marrow transplants

We studied engraftment in a murine model of allogeneic bone marrow (BM) transplantation. Recipient C57BL/6 (H-2b) mice were conditioned with single-dose (9 or 7.5 Gy) total body irradiation (TBI), fractionated (4 X 3.3 Gy) TBI, hyperfractionated (8 X 1.65 Gy) TBI, 2 X 120 mg/kg cyclophosphamide (CY) followed by 7.5 Gy TBI, or 300 mg/kg CY followed by 9 Gy total lymphoid irradiation (TLI). Conditioned mice were transplanted with BALB/c (H-2d) BM supplemented with splenocytes (BMS) to facilitate graft-vs-host disease (GVHD). Ex vivo T cell depletion of the BMS with anti-Thy-1.2 antibody and complement protected recipients from lethal GVHD. Engraftment was measured in transplanted animals by serotyping peripheral blood mononuclear cells with anti-H-2-specific antibodies and complement. Mice that were given a T cell-depleted BMS transplant after conditioning with 9 Gy TBI, fractionated TBI, or CY plus TBI showed a 99 to 100% incidence of engraftment. However, if the T cell-depleted graft was given to mice conditioned with hyperfractionated TBI, 7.5 Gy TBI, or CY plus TLI, only 3 to 32% of the animals engrafted. BM which was not T cell-depleted engrafted in 63 to 100% of the mice regardless of the conditioning used. Nonengrafted mice tested with anti-host type antibody demonstrated autologous recovery. We conclude that engraftment or failure/rejection of BM in transplanted mice is determined in part by a dynamic equilibrium between T cells present in the donor graft and the surviving hemopoietic cells in the conditioned recipient. More intensive conditioning of the recipient allows engraftment of T cell-depleted, mismatched BMS. Such conditioning is not limited to a single modality, but can be achieved with single-dose TBI, fractionated TBI, or with TBI combined with CY. These findings have timely and important implications for the current understanding of engraftment in human allogeneic BM transplantation following T cell depletion.     

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)     

Autoreactive T cells in MRL/Mpr-lpr/lpr mice. Characterization of the lymphokines produced and analysis of antigen-presenting cells required

Lymph node cells from 4-wk-old MRL/Mp-lpr/lpr mice, but not from MRL/Mp-+/+ mice, when cultured in vitro for 5 to 7 days, will spontaneously proliferate and produce IL-2. We examined the expression of several cell surface Ag on lymph node cells from MRL/Mp-lpr/lpr mice before and after in vitro culture. There is an increase in the expression of Thy-1, L3T4, IL-2R, T cell activating protein, T cell receptor, and T3 complex on the surface of cultured cells. Cultured cells produced IL-3, IFN-gamma, and small but detectable amounts of IL-1 in addition to IL-2. Gamma irradiation of APC from young MRL/Mp-lpr/lpr mice or treatment of APC with a mAb (J11D) and C, completely abrogated their stimulatory capacity. These experiments suggest that B cells are the predominant APC responsible in the activation of autoreactive T cells in MRL/Mp-lpr/lpr mice. Lymph node cells from C57BL/6-lpr/lpr or C3H-lpr/lpr mice were unable to spontaneously proliferate or produce IL-2. Lymph node cells from (MRL/Mp-lpr/lpr x C57BL/6-lpr/lpr) F1 mice or (C3H-lpr/lpr x MRL/Mp-lpr/lpr) F1 mice did proliferate and produced IL-2 after in vitro culture. Using T cells from these F1 animals and APC from each parental haplotype, we found that APC from MRL/Mp-lpr/lpr mice induced more proliferation and greater amounts of IL-2, when compared to APC from F1 animals. APC from C57BL6-lpr/lpr mice or C3H-lpr/lpr were unable to induce spontaneous proliferation and IL-2 production. Therefore, B cells from MRL/Mp-lpr/lpr mice appear to possess unique features that enable them to activate autoreactive T cells more effectively than B cells from other mice bearing the lpr/lpr gene.     

Autoimmune CD4+ T cells interfere with immune tolerance to a thymic-independent antigen

The ability of autoimmune T cell subsets to interfere with tolerization of B cells can be studied by using thymic-independent Ag. We have defined an abnormality within the CD4+ T cell compartment in young NZB and MRL-lpr/lpr mice by studying tolerance of spleen and B cells to the thymic independent Ag, fluorescein-Brucella abortus. Tolerization of spleen cells is defective in MRL-lpr/lpr mice, but not MRL-+/+ or C3H.lpr mice, suggesting that the defect requires both the autosomal MRL background and the lpr gene to be present. T enriched cells from NZB mice and from MRL-lpr/lpr mice (but not MRL-+/+ or C3H.lpr mice) reverse tolerance in spleen cells from [NZB X DBA/2]F1 and C3H/HeJ mice, respectively. This interference is removed by treatment with anti-CD4 antibody and C. Supernatants from cultured T cells of NZB and MRL-lpr/lpr mice also prevent tolerance in spleen cells of [NZB X DBA/2]F1 and MRL-+/+ mice, respectively, unless CD4+ cells are removed prior to T cell culture. Removal of T cells from NZB and MRL-lpr/lpr spleen cells allows normal tolerization of B cells, which is abrogated by the addition of syngeneic T cells or cultured T cell supernatants. This effect also depends on the presence of CD4+ T cells. These studies show that in MRL-lpr/lpr mice, through interaction of the lpr and MRL background genes in a T cell subset, and in NZB mice, CD4+ T cells interfere with B cell tolerance to a thymic-independent Ag.     

B cells are required for lupus nephritis in the polygenic, Fas-intact MRL model of systemic autoimmunity.

B cells are required for both the expression of lupus nephritis and spontaneous T cell activation/memory cell accumulation in MRL-Faslpr mice (MRL/lpr). Autoimmunity in the MRL/lpr strain is the result of Fas-deficiency and multiple background genes; however, the precise roles of background genes vs Fas-deficiency have not been fully defined. Fas-deficiency (i.e., the lpr defect) is required in B cells for optimal autoantibody expression, raising the possibility that the central role for B cells in MRL/lpr mice may not extend to MRL/+ mice and, thus, to lupus models that do not depend on Fas-deficiency ("polygenic lupus"). To address this issue, B cell-deficient, Fas-intact MRL/+ mice (JHd-MRL/) were created; and disease was evaluated in aged animals (>9 mo). The JHd-MRL/+ animals did not develop nephritis or vasculitis at a time when the B cell-intact littermates had severe disease. In addition, while activated/memory CD4+ and CD8+ T cells accumulated in B cell-intact mice, such accumulation was substantially inhibited in the absence of B cells. This effect appeared to be restricted to the MRL strain because it was not seen in B cell-deficient BALB/c mice (JHd-BALB) of similar ages. The results indicate that B cells are essential in promoting systemic autoimmunity in a Fas-independent model. Therefore, B cells have an important role in pathogenesis, generalizable to lupus models that depend on multiple genes even when Fas expression is intact. The results provide further rationale for B cell suppression as therapy for systemic lupus erythematosus.     

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.     

Unresponsiveness of MRL/MP-lpr/lpr mice to antigen given subcutaneously in adjuvant: partial restoration of response after local injection of B cells

MRL/lpr mice were used as a model for seeking information on the role of B cells as antigen-presenting cells in vivo. In confirmation of the finding of other workers, MRL/lpr mice with pronounced lymphadenopathy failed to undergo T cell priming in lymph nodes (LN) after s.c. injection of keyhole limpet hemocyanin (KLH) in complete Freund's adjuvant (CFA): thus, in contrast to normal mice or young MRL/lpr mice, the LN cells from older MRL/lpr mice failed to give secondary T proliferative responses to the injected antigen in vitro. Because previous work from this laboratory has shown that B cells play a major role in priming T cells in LN of normal mice, we tested the possibility that the lack of T cell priming to KLH seen in older MRL/lpr LN reflected the relative paucity of B cells. To test this idea, MRL/LPR mice were injected s.c. with B cells taken from normal or young MRL/lpr mice 1 day before priming with KLH/CFA. In the case of old (20 to 24 wk) MRL/lpr mice with massive lymphadenopathy, prior injection of B cells had virtually no effect in promoting LN priming. In marked contrast, injection of B cells into mice exhibiting less-pronounced LN enlargement (mice tested at 14 to 16 wk) was highly effective in restoring LN priming; before B cell injection, the LN of these mice contained only 2 to 5% B cells. These findings add to the evidence that T cell priming in LN is heavily dependent on the presence of B cells.     

CD4+ T cells generated de novo from donor hemopoietic stem cells mediate the evolution from acute to chronic graft-versus-host disease

Acute and chronic graft-versus-host disease (GVHD) remain the major complications limiting the efficacy of allogeneic hemopoietic stem cell transplantation. Chronic GVHD can evolve from acute GVHD, or in some cases may overlap with acute GVHD, but how acute GVHD evolves to chronic GVHD is unknown. In this study, in a classical CD8+ T cell-dependent mouse model, we found that pathogenic donor CD4+ T cells developed from engrafted hemopoietic stem cells (HSCs) in C57BL/6SJL(B6/SJL, H-2(b)) mice suffering from acute GVHD after receiving donor CD8+ T cells and HSCs from C3H.SW mice (H-2(b)). These CD4+ T cells were activated, infiltrated into GVHD target tissues, and produced high levels of IFN-gamma. These in vivo-generated CD4+ T cells caused lesions characteristic of chronic GVHD when adoptively transferred into secondary allogeneic recipients and also caused GVHD when administered into autologous C3H.SW recipients. The in vivo generation of pathogenic CD4+ T cells from engrafted donor HSCs was thymopoiesis dependent. Keratinocyte growth factor treatment improved the reconstitution of recipient thymic dendritic cells in CD8+ T cell-repleted allogeneic hemopoietic stem cell transplantation and prevented the development of pathogenic donor CD4+ T cells. These results suggest that de novo-generated donor CD4+ T cells, arising during acute graft-versus-host reactions, are key contributors to the evolution from acute to chronic GVHD. Preventing or limiting thymic damage may directly ameliorate chronic GVHD.     

The Igh-V locus of MRL mice: restriction fragment length polymorphism in eleven strains of mice as determined with VH and D gene probes

The MRL strain of mice is a model system that closely parallels the human autoimmune disease systemic lupus erythematosus. Our analysis of the variable region genes of MRL mice showed that the MRL/lpr D genes were similar to those of the C3H mouse (Igh-C allotype j). This result was unexpected, because previous studies of the MRL/lpr and MRL/+ substrains suggested that they are allotype a at the Igh-1 (gamma 2a) locus of the constant region. The Igh-V (heavy chain variable region) locus of the MRL/lpr and MRL/+ strains of mice and their parents were therefore examined by restriction fragment length polymorphism with probes for the DSP2 and DFL16 gene families and with two cloned VH probes. Five other strains of mice were also included because the heavy chain locus of the LG mouse, which is the major progenitor of the MRL strains, has not been studied. The MRL substrains and the LG and C3H parents were indistinguishable at all the Igh-V loci studied. These results suggest that the MRL substrains and their LG parent are haplotype j at the Igh-V locus. The results obtained with D gene probes show that the DSP2 gene family is more polymorphic than the DFL16 gene family, which is relatively conserved. We have assigned Igh-V haplotypes for the four VH loci to the 11 strains of mice studied.     

Evidence for an intrinsic B cell defect in lpr/lpr mice apparent in neonatal chimeras

Stem cells from a lpr/lpr mouse do not cause the lpr syndrome characteristic of unmanipulated MRL/lpr mice when injected into nonautoimmune neonatal mice. Instead, these neonatal chimeras gradually become markedly lymphopenic. As adults, only limited donor cell engraftment (approximately 5%) was evident as assessed by cell surface staining of H-2D or Thy-1 allelic markers. However, the relatively low number of lpr/lpr-derived B cells produced greater than 90% of the circulating IgG2a antibody and all detectable IgG2a anti-ssDNA autoantibody, indicating that lpr/lpr B cells express an intrinsic genetic defect resulting in hyper-IgG and autoantibody secretion.     

Influence of the Ig H chain locus on autoantibody production in autoimmune mice.

Autoimmune disease is influenced by multiple genes. In this study, we investigated the role of one genetic locus, Ig H chain. IgG2a antichromatin, anti-ssDNA, and antihistone autoantibodies (autoAb) from (MRL/Mp-lpr/lpr x C57BL/6-lpr/lpr), (Ighj/b); (C57BL/6-lpr/lpr x C57BL/6-lpr/lpr-Igha), (Ighb/a); and (MRL/Mp-lpr/lpr x MRL/Mp-lpr/lpr-Ighb), (Ighj/b) mice were determined using allotype-specific ELISA. Strikingly, antichromatin and antihistone antibodies (Ab) were comprised of significantly more b allotype than either a or j allotype in all cohorts of F1 mice examined. In mice that produced anti-Sm Ab, the b allotype was used preferentially for these autoAb as well. However, no allotype skewing was observed in IgG2a Ab directed against TNP or DNA, or for total IgG2a. An Igh recombinant locus was utilized to examine the genetic control of b allotype skewing in lpr mice and in chronic graft vs host disease. In both models, the VH region did not appear to be responsible for the preferential use of b allotype. These results indicate a contribution to autoimmunity by the Igh locus and raise the possibility that Ig allotype may influence autoimmune disease by its effect on the production of certain autoAb.     

Bone marrow transplantation across major histocompatability barriers in mice. III. Treatment of donor grafts with monoclonal antibodies directed against Lyt determinants

We studied the effect of eliminating T cells from donor grafts of mice in a system in which bone marrow was transplanted across major histocompatibility barriers. BALB/c bone marrow (added as a source of hematopoietic stem cells) combined with equal volumes of spleen cells (added as a source of GVHD-promoting cells) was pretreated in vitro with monoclonal anti-Lyt-1.2 or Lyt-2.2 plus absorbed rabbit complement before injection into C57BL/6 total-body-irradiated recipients. Functional activity of anti-Lyt monoclonal antibodies was determined in CML assay. Treatment with anti Lyt-1.2 plus C did not have any anti-stem cell activity, as measured by CFU-S assay, and protected recipients from the onset of lethal GVHD. Treatment with Lyt-2.2 plus C also did not reduce CFU-S; however, mice receiving treated marrow did develop GVHD and were all dead by 2 mo, as were untreated control mice. Surviving "anti-Lyt-1.2 + C chimeras" demonstrated a high percentage of donor mononuclear cells in their peripheral blood. Similar results were obtained when C3H/HeN donor BMS was treated with monoclonal anti-Lyt-1.1 plus C and injected into C57BL/6 recipients. These findings show that monoclonal antibodies directed against determinants unrelated to Thy-1 can eliminate T cells in the presence of C and successfully protect transplanted mice from lethal GVHD. They also suggest that these anti-Lyt antibodies may be useful tools in determining subpopulations of T cells that contribute to the development of GVHD.     

Gammadelta T cells promote a Th1 response during coxsackievirus B3 infection in vivo: role of Fas and Fas ligand

Fas/Fas ligand (FasL) interactions regulate disease outcome in coxsackievirus B3 (CVB3)-induced myocarditis. MRL(+/+) mice infected with CVB3 develop severe myocarditis, a dominant CD4(+) Th1 (gamma interferon [IFN-gamma(+)]) response to the virus, and a predominance of gammadelta T cells in the myocardial infiltrates. MRL lpr/lpr and MRL gld/gld mice, which lack normal expression of Fas and express a mutated FasL, respectively, have minimal myocarditis and show a dominant CD4(+) Th2 (interleukin-4 [IL-4(+)]) phenotype to CVB3. Spleen cells from virus-infected wild-type, lpr, and gld animals proliferate equally to virus in vitro. Adoptive transfer of gammadelta T cells from hearts of CVB3-infected MRL(+/+) mice (FasL(+)) into infected MRL gld/gld recipients (FasL(-)/Fas(+)) restores both disease susceptibility and Th1 cell phenotype. However, transfer of these cells into MRL lpr/lpr recipients (FasL(+)/Fas(-)) did not promote myocarditis and the viral response remained Th2 biased. This paralleled the expression of very high surface levels of FasL by myocardial gammadelta T cells, as well as their propensity to selectively lyse Th2 virus-specific CD4(+) T cells. These results demonstrate that Fas/FasL interactions conferred by gammadelta T cells on lymphocyte subpopulations may regulate the cytokine response to CVB3 infection and pathogenicity.     

Bone marrow-derived cells are essential for intrathymic deletion of self-reactive T cells in both the host- and donor-derived thymocytes of fully allogeneic bone marrow chimeras

The fate of self-reactive T cells was examined in both the host- and donor-derived thymocytes of fully allogeneic bone marrow (BM) chimeras of two strain combinations of AKR/J (H-2k, IE+, Thy-1.1, Mls-1a2b) and C57BL/6 (H-2b, IE-, Thy-1.2, Mls-1b2b). Sequential appearance of host- and donor-derived T cells occurred in the thymus of both AKR----B6 and B6----AKR chimeras in which 5 x 10(6) of T cell-depleted BM cells were used to reconstitute recipients lethally irradiated with 950 rad. Thymocytes bearing V beta 6 high, which recognize MHC class II IE-binding Ag encoded by Mls-1a allele, were detected in neither host- nor donor-derived thymocytes of AKR-B6 chimeras in which Mls-1a and IE were expressed only by the BM-derived cells. Thymocytes bearing V beta 11high capable of recognizing IE were also deleted in the host- and donor-derived thymocytes of the AKR----B6 chimeras. One million of BM cells were inadequate to deletion of the B beta 6high and V beta 11high T cells in the host-derived thymocytes of these chimeras. On the other hand, significant number of V beta 6high and V beta 11high thymocytes were detected in both the host- and donor-derived thymocytes in B6----AKR chimeras where sufficient dose of IE- stem cells were used to reconstitute irradiated Mls-1aIE+ recipients. These results suggest that clonal deletion of the host- and donor-reactive T cells in both the host- and donor-derived thymocytes is an important mechanism for the induction of transplantation tolerance in allogeneic BM chimeras and that BM-derived APC may be essential for the intrathymic elimination of both the host- and donor-reactive T cells in the BM chimeras.     

Effect of graft-versus-host disease on anti-tumor immunity

BCL1, a spontaneous B cell leukemia of BALB/c origin, is rejected by C.B-20 (Ighb, H-40b) but not BALB/c (Igha, H-40a) mice. Adoptive transfer of C.B-20 anti-BCL1 effector cells specific for the minor histocompatibility Ag H-40a protects irradiated C.B-20 but not BALB/c recipients. Because C.B-20 donor cells could potentially generate graft-vs-host disease (GVHD) in BALB/c recipients, we investigated the possibility that GVHD prevents the anti-tumor effect. GVHD was induced in (C.B-20 X B10.D2)F1 [H-2d, H-40b X H-2d,H-40b] recipients after injection of B10.D2-primed C.B-20 donor cells. GVHD was indicated by the histologic appearance of tissue sections from C.B-20----F1 livers, target organs of GVHD, which showed a marked mononuclear cell infiltrate around the portal tracts and central veins. In addition, splenic lymphocytes from these mice had altered CD4/CD8 ratios and were unable to respond to the polyclonal activators Con A and LPS. The mitogen unresponsiveness was at least partially due to the presence of a suppressor cell, because proliferation of normal spleen cells to Con A and LPS was suppressed upon addition of C.B-20----F1 spleen cells. Further immune dysfunction was evident by the inability of T cells from mice with GVHD to generate a CTL response to H-2 alloantigens. Addition of C.B-20----F1 spleen cells to F1 responder cells at the induction of culture did not prevent generation of CTL, indicating that a suppressor cell was not responsible for the lack of CTL activity. In this setting of GVHD, F1 recipients were able to reject BCL1 upon adoptive transfer of C.B-20 anti-BCL1 effector cells. These data indicate that GVHD-induced immune dysfunction does not inhibit the activity of antileukemia T cells.