Reactivation of allergic encephalomyelitis by means of allogeneic confrontation

Lewis rats recovered from experimental allergic encephalomyelitis (EAE) are resistant to active reinduction of disease. (DA X Lewis)F1 hybrids behave in an identical fashion. The induction of a graft versus host (GVH) reaction in EAE convalescent (DA X Lewis)F1 rats, by injection of normal parental (Lewis) lymphocytes, precipitates a second episode of EAE in a proportion of rats. This secondary episode of EAE can be induced by injection of parental cells either systemically (intravenously) or locally (subcutaneously in the foot). A host versus graft (HVG) reaction does not reactivate EAE in the convalescent host. The observed effect is probably due to reactivation of EAE effector cells following the extensive nonspecific proliferation of host lymphoid cells which is a feature of GVH reactivity.     

Specific selection of cytotoxic effector cells: the generation of cytotoxic T cells in rat thoracic duct lymphocyte populations positively or negatively selected for reactivity to specific strong histocompatibility alloantigens.

These studies consider the generation of cytotoxic T lymphocytes (CTL) from precursors (CTLP) present in rat thoracic duct lymphocytes after stimulation with strong alloantigens. Also, they explore the relationship between CTLP and "initiator" (I) lymphocytes responsible for specific GVH and MLI reactions. Positively selected TDL populations prepared in bulk MLI cultures show enriched GVH and MLI reactivity for the selecting major histocompatibility complex (MHC) haplotype, but no cytotoxic activity, raising the possibility that I and CTLP may belong to different subpopulations, and the latter failed to differentiate or to survive under these culture conditions. Restimulation of these cells in Marbrook culture vessels with the original priming haplotype under conditions suitable for generating killer cells in vitro resulted in greatly increased specific CTL activity with accelerated kinetics soon after priming and normal kinetics later. These findings indicate that "memory" killer cells can be generated in a previously stimulated lymphocyte population that had no overt cytotoxic activity. Restimulation with third party haplotypes failed to give CTL activity either to specific or to third party targets. Negatively selected TDL populations prepared by "filtration" through x-irradiated F1 rats, depleted of specific GVH and MLI responses, were also depleted of the ability to generate CTL in Marbrook cultures stimulated with the selecting haplotype. Stimulation with third party haplotypes, or with both third party and specific haplotypes together, gave CTL effective only against the third party target.     

SPECIFIC positive and negative selection of rat lymphocytes reactive to strong histocompatibility antigens: activation with alloantigens in vitro and in vivo.

This study compares the functional properties of rat thoracic duct lymphocytes (TDL) after stimulation with strong alloantigens of the major histocompatibility complex (MHC) either in vitro in preparative mixed lymphocyte interactions (MLI) or in vivo in systemic graft-vs-host (GVH) reactions. Comparisons were made of PHA responses and reactivity to the specific priming haplotypes or to third party haplotypes in analytical MLI and in GVH reactions either before or after the activated populations were "parked" in syngenetic T cell-deprived (B) rats. These comparisons can be summarized as follows: 1) TDL populations primed in bulk MLI cultures (MLI-TDL) slowed some evidence of specific positive selection when tested immediately; MLI responses to specific alloantigens were both relatively large and accelerated in tempo, whereas responses to third party alloantigens were diminished but also accelerated in tempo. Specific GVH responses were more marked than in third party recipients but they were also decreased relative to normal, and displayed an abberant dose/response slope. MLI-TDL populations tested after they had been stored in syngeneic B rats showed clear evidence of stable-specific positive selection; specific MLI and GVH responses were enriched relative to third party responses and also in comparison to normal, unselected TDL populations. This finding indicates that GVH and MLI reactivity are probably both functional capacities of the same lymphocyte subpopulation since positive selection by one function (MLI) also enriched for a second (GVH). 2) Parental strain TDL activated in vivo in the systemic GVH reaction in irradiated F1 animals and recovered from the thoracic duct 3 to 4 days later (late GVH-TDL) consisted mainly of blast cells, however, in contrast to MLI-TDL these populations showed no evidence of positive selection when tested before or after parking in B rats. MLI responses to specific alloantigens were minimal, and greatly reduced in magnitude compared to normal. GVH responses to specific haplotypes could be detected, but these were not enriched compared to normal, despite the content in the late GVH-TDL populations of a significant proportion of blast cells presumably activated by host alloantigens. 3) Early collections (less than 40 hr) of parental strain GVH-TDL collected from F1 recipients contained no blast cells and showed impressive degrees of negative selection; they were markedly depleted of both GVH and MLI activity to specific alloantigens but displayed normal reactivity to third party alloantigens. Moreover, specific negative selection was persistent in these populations parked for several weeks in B rats, and indication that a specific subpopulation of reactive cells had been physically eliminated. 4) PHA responses of both MLI- and GVH-activated TDL populations tested either before or after parking in B rats were approximately normal on a per T cell basis...     

Semisyngeneic transplantation of hematopoietic cells of native and cultured embryonic liver

The protective ability and graft-versus-host (GVH) activity in parental strain hematopoietic fetal liver cells (FLC) transplanted to irradiated F1 hybrids were evaluated quantitatively. A 21-day survival of more than 80% of semi-syngeneic mouse recipients required the injection of 2-5 X 10(6) nucleated fetal liver cells (FLC). The same effect could be obtained with FLC cultivated for 4-15 days. 5 to 25 X 10(6) parental FLC were necessary to induce a considerable GVH mortality within 2-3 months after transplantation. Thus, the minimal cell doses of both native and cultivated FLC enough for the maximal protective effect have proved ineffective for the provocation of the fetal GVH disease. Hematopoietic cells from long-term FLC cultures had a low protective potential though they could contain high CFUs concentration. This discrepancy shows clearly that such polypotent precursors as CFUs have no ability to restore hematopoiesis, in other words they cannot be totipotent stem cells.     

Interleukin-1 induced gene expression of neutrophil activating protein (interleukin-8) and monocyte chemotactic peptide in human synovial cells

We report here that human synovial cells stimulated by interleukin-1 alpha and interleukin-1 beta express mRNA for both IL-8 (neutrophil chemotactic peptide) and monocyte chemotactic protein. IL-1 stimulated synovial cells from both osteoarthritis and rheumatoid arthritis patients exhibited similar mRNA expression of interleukin-8 and monocyte chemotactic protein. A capacity to produce factors selectively chemotactic for neutrophils, lymphocytes and monocytes provides a mechanism whereby synovial cells can facilitate inflammatory arthritis.     

Inhibition of mouse bone marrow granulocyte-macrophage colony formation by factors derived from natural killer cells: an in vitro model for hybrid resistance

Investigations were performed to study whether soluble factors produced by NK-cells could mediate "hybrid resistance" in vitro. NK-cells enriched from spleens of B6D2F1 hybrid mice were incubated with parental B6 bone marrow, and the effect of the derived supernatants on the development of granulocyte-macrophage colony forming cells (GM-CFC) was assessed. Cell free supernatants obtained from low density cells (LDC) of B6D2F1 hybrids stimulated with bone marrow cells (BMC) from B6 mice inhibited GM-CFC formation. The inhibition was similar using B6, D2 or B6D2F1 bone marrow cells as the targets for GM-CFC growth. Our findings suggest that NK cells from F1 hybrid mice when stimulated with BMC from B6 mice release inhibitory factors, different from IFN-gamma and that this production may represent a mechanism of natural resistance to parental H-2b bone marrow grafts.     

Altered N-glycosylation in macrophage x melanoma fusion hybrids.

It was recently reported that a majority of hybrids generated in vitro between weakly metastatic mouse Cloudman S91 melanoma cells and human or mouse macrophages showed enhanced metastatic potential (Rachkovsky et al., 1998). With few exceptions, hybrids with enhanced metastatic potential also had elevated basal melanin content, enhanced chemotactic responses to fibroblast-conditioned media, and stronger responsiveness to MSH compared to parental cells. Analyses revealed that altered N-glycosylation in metastatic hybrids could explain the multiple phenotypic changes. Tyrosinase, TRP-2 and LAMP-1 from hybrids migrated more slowly on gels compared to the same proteins from parental melanoma cells, consistent with increased glycosylation. Migration of LAMP-1 from hybrids was similar to that from peritoneal macrophages which also appeared to be more heavily glycosylated than LAMP-1 from Cloudman cells. The incorporation of 3H-glucosamine, as a marker of N-glycosylation, into tyrosinase and LAMP-1 was found to be elevated in hybrids, suppressed by N-glycosylation inhibitors and stimulated by MSH to a greater degree in hybrids compared to parental cells. These results indicate N-glycosylation as an important regulatory pathway for MSH-induced melanogenesis, and further suggest that altered N-linked glycosylation may be an underlying mechanism for regulation of both melanogenesis and metastasis in macrophage x melanoma hybrids.     

Graft-vs-host reactions in F1 mice induced by parental lymphoid cells: nature of recruited F1 cells.

Graft versus host (GVH) reactivity of parental lymph node (LN) cells was assayed by measurements of 3H-thymidine incorporation in vivo. Mitomycin (Mit.) treatment of parental cells abolished their proliferative activity but the combination of such Mit.-treated parental cells with F1 LN cells resulted in much higher proliferation than either one population alone. This recruitment into proliferation of F1 cells was prominent on days 3 and 4 after cell injection and amounted to 35 to 51% of the total activity seen after injection of untreated parental cells alone. The F1 cell sensitive to recruitment was resistant to anti-Thy 1.2 treatment, was not removed by carbonyl iron-magnet separation; and was not present in thymus. The parental cell inducing recruitment was, however, sensitive to anti-Thy 1.2. When spleen cells from hapten immune F1 donors were injected together with Mit.-treated parental LN cells and boosted with hapten on another carrier, a typical "allogeneic effect" was observed in the anti-hapten immune response. It was concluded that Mit.-treated parental T cells exerted a mitogenic effect on F1 B cells resulting in extensive recruitment similar to that seen in murine mixed lymphocyte reactions.     

The role of B lymphocytes in cell-mediated immunity II. Delayed hypersensitivity induced by dinitrophenyl-ficoll in dinitrophenyl-keyhole limpet hemocyanin-immunized guinea pigs.

Dinitrophenyl (DNP)-Ficoll will elicit typical delayed hypersensitivity skin reactions in guinea pigs immunized with DNP-keyhole limpet hemocyanin (KLH). We observed that lymph node cells (LNC) from these animals produced the lymphokine, monocyte chemotactic factor (MNL CTX) when stimulated by DNP-Ficoll in vitro. This response was antigen and hapten specific since LNC from nonimmune guinea pigs or those immunized with nonDNP containing antigens were not stimulated by DNP-Ficoll. Lymph node cells were fractionated into T- and B-cell-enriched populations to determine the nature of the DNP-Ficoll-responsive cell. Only the B-lymphocyte-enriched population produced MNL CTX in response to DNP-Ficoll. The purity of the B-cell population was demonstrated by its failure to respond to PHA and by the fact that B cells derived from DNP-although they could no longer respond without T-cell help to the T-dependent antigen, DNP-OVA. These findings suggest that the hapten-specific response of guinea pigs to DNP-Ficoll may be a form of B-cell-mediated delayed hypersensitivity.     

Graft-vs-host reactions (GVHR) across minor murine histocompatibility barriers. I. Impairment of mitogen responses and suppressor phenomena

In our laboratory, we have developed a murine model to examine GVHD across minor histocompatibility antigens. In our model, GVHD is induced by injecting B10.D2 spleen cells into irradiated BALB/c recipients. Seven to 10 days after irradiation and injection of cells, there are significant changes in cell function in the recipient spleens. In the B10.D2----BALB/c (600 rad) model, recipient spleen cells are profoundly unresponsive to Con A and LPS stimulation but show increased B cell activity measured by Staphylococcus aureus protein A plaque-forming activity. Spleen cells from such GVH mice profoundly suppress the mitogenic responses of normal BALB/c or B10.D2 spleen cells to Con A and LPS. The degree of impairment of the mitogenic response and the ability to suppress normal cells is proportional to the dose of cells used to induce GVH reactions. Both the inability to respond to mitogens and the capacity to suppress are also related to the dose of irradiation given to the recipients. In addition, immunosuppression across minor histocompatibility antigens shows an unevenhandedness. If we inject parental B10.D2 or BALB/c cells into F1 recipients (P----F1), there is greater inhibition of mitogenic responses when B10.D2 parental cells are given than when BALB/c cells are given to the irradiated F1 recipients. These experiments show that significant immunosuppression occurs during GVH reactions across minor histocompatibility barriers. The degree of suppression varies according to the dose of cells used to induce GVH, the dose of irradiation to the recipient and the "strength" of the GVH recognition system. Such experiments provide models for GVH disease seen in humans who receive treatment for leukemia or other diseases that involves recipient irradiation and infusion of HLA-identical bone marrow.     

Cell-mediated suppression of the fifth component of complement in mice.

Suppression of levels of circulating C5 in (C5- C5+)F1 hybrids by administration of (C5- C5-) parental lymphoid cells in the neonatal period has been accomplished with the three strain combinations tested ((SWR X RIII)F1, (A/He x RIII)F1, and (SWR X DBA/1)F1). Suppression was shown to be specific for C5 and not accompanied by reductions of C1, C2, C6, or other major groups of blood proteins. This demonstrated that the C5 reduction was not due to activation of complement (C) with resultant hypercatabolism of C components. When there was a concurrent chronic GVH reaction induced by lymphoid cells administered to offspring of H-2 incompatible parents, there was usually a resultant hypergammaglobulinemia that was also unrelated to the presence or absence of C5 suppression. Effective suppression required preimmunization of either the cell donor, the mother of the F1 hybrids, or both. This suggests that either two cell types or a single cell plus a humoral factor are required for suppression in this system.     

Fate of H2-activated T lymphocytes in syngeneic hosts. III. Differentiation into long-lived recirculating memory cells.

Memory to H2 determinants was studied with an adoptive transfer system using a population of H2-activated blast T cells (T.TDL) obtained from thoracic duct lymph of irradiated F₁ hybrid mice injected with parental strain T cells. CBA T.TDL activated either to DBA/2 or C57BL determinants were transferred to syngeneic “B” mice. Thoracic duct lymphocytes (TDL) were obtained from the recipients 4–6 weeks later and tested for their capacity to produce (a) a graft-versus-host (GVH) reaction, (b) a mixed lymphocyte reaction (MLR) (measured by an in vivo technique) and (c) allograft rejection (suppression of the growth of allogeneic tumour cells in vivo). Control experiments involved testing the function of TDL obtained from “B” mice preinjected with TDL or no cells.TDL from “B” mice injected with TDL (passaged TDL) gave strong MLR and GVH reactions to both DBA/2 and C57BL determinants. Passaged T.TDL activated to C57BL antigens gave intermediate MLR and GVH reactions to the specific (C57BL) determinants but only very low responses to third-party (DBA/2) determinants; reciprocal results were obtained with passaged T.TDL activated to DBA/2 determinants. TDL from “B” mice given no cells failed to respond to either set of determinants.Since the responses by the passaged T.TDL did not exceed those by passaged TDL there was no evidence that adoptive transfer of T.TDL had conferred to the recipients a state of memory to either MLR or GVH determinants. Adoptive transfer did, however, lead to qualitative changes in the properties of T.TDL since, before transfer, they were unable to evoke GVH reactions or produce an MLR of normal kinetics.Passaged T.TDL were far superior to passaged TDL at suppressing the growth of allogeneic tumour cells. The protection was specific since protection against DBA/2 tumour cells was, cell for cell, 5–10 fold more effective with passaged T.TDL activated to DBA/2 determinants than with cells activated to C57BL determinants. No protection was observed with cells treated with anti-θ serum. The protective cells appeared to be precursors of effector cells rather than effector cells per se since they failed to lyse the tumour cells in vitro. These data suggest therefore that the descendants of T.TDL which survived after transfer to “B” mice were highly enriched in long-lived recirculating T lymphocytes reactive to determinants expressed by specific tumour allografts.     

Interleukin 2 receptor dysfunction in mice undergoing a graft-vs-host reaction

Mice of the (C57BL/10 X B10.A)F1 combination were given a single i.v. inoculation of 3 to 4 X 10(7) B10.A spleen cells, which induces a graft-vs-host (GVH)-associated immune deficiency in F1 mice. Between 1 and 4 wk later, spleen cells from the F1 mice were tested for the expression of IL 2 receptors by flow microfluorometry, using the 7D4 rat monoclonal antibody directed against an epitope murine IL 2 receptor. A reduction in intensity of spleen cell staining with 7D4 was detected as early as 8 days after parental cell inoculation, and no IL 2 receptors were detected by 28 days after initiation of GVH. Furthermore, the loss of IL 2 receptors was correlated with abrogation of proliferative responses to concanavalin A and lipopolysaccharide, of IL 2 production, and of cytotoxic T lymphocyte responses. These observations may be relevant for our understanding of GVH reactions, of immune disorders associated with GVH, and possibly of primary and acquired immunodeficiencies in general.     

Immunosuppression of normal lymphoid cells by serum from mice undergoing chronic graft-vs-host disease.

Spleen cells from F1 mice undergoing chronic graft-vs-host (GVH) reaction, induced by injection of parental cells, were shown to be immunosuppressed since their in vitro responses to the mitogens concanavalin A (Con A) and bacterial lipopolysaccharide (LPS) were substantially lower than control animals. Serum, from mice undergoing GVH, when cultured in vitro with normal spleen cells was immunosuppressive. The proliferation response to Con A and allogeneic cells of normal syngeneic, allogeneic, and parental spleen cells was 90% suppressed when serum from mice undergoing chronic GVH was added in comparison to the addition of serum from untreated F1 mice. Similarly, the in vitro antibody response to a T-dependent antigen was impaired; however, the antibody response to a T-independent antigen was not impaired. These results indicate that T cell functions are more sensitive than are B cell functions to immunosuppressive factors in the serum of mice undergoing GVH.     

Metallic tin-induced lymphadenopathy in rat strains and hybrids

Metallic tin powder, injected into Lewis rats obtained from three different sources, caused enlargement of the regional draining lymph nodes. The histopathology featured epithelioid cell granulomas around phagocytosed particles of tin and an intense hyperplasia of plasma cells. The same material injected into August rats enlarged the lymph nodes but the enlargement was caused by granulomas without a major concomitant plasma cell response. In most other strains, tin produced less lymph node enlargement and the plasma cell response was minimal. However, F1 hybrids of Lewis rats with either the August, Brown-Norway (BN), or Dark Agouti (DA) strains developed plasma cell hyperplasia similar to that seen in the parental Lewis strain. The response to tin was the same whether the tin was injected into the feet or into the peritoneal cavity. Thus, the lymph node response to metallic tin varied from a slight, banal response to insoluble foreign particles, to an exuberant granulomatous hyperplasia, to an intense plasmacellular hyperplasia, depending on the genetic characteristics of the subjects.     

Effect of allogeneic cell interaction and graft-versus-host reaction on the antibody response to Escherichia coli 0127 antigen.

The influence of allogeneic cell interaction and GVH reaction on the immune response to Escherichia coli antigen was investigated. Addition of CBA/J spleen cells to cultures of nu/nu spleen cells stimulated a significant increase in the nude PFC response to SRBC but had no significant effect on the immune response to E. coli antigen. Similarly, the induction of a GVH reaction in F₁ mice by the injection of parental spleen cells also had no significant effect on the immune response to the bacterial antigen. These results suggest that the immune response to E. coli is not affected by products of thymus-derived cells.     

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.     

Autoimmunization in murine graft-vs-host disease. I. Selective production of antibodies to histones and DNA

A lupus-like disease characterized by a severe immune complex glomerulonephritis and IgG autoantibody production was induced in (C57BL/6 X DBA/2)F1 mice by injection of parental DBA/2 lymphoid cells. The ensuing graft-vs-host (GVH) reaction resulted in a 10- and a 100-fold increase in serum IgG antibody levels to denatured DNA and total histones, respectively, compared with that in F1----F1 control mice. The level of anti-DNA antibodies peaked 2 wk after injection of DBA/2 cells and preceded peak anti-histone levels by approximately 2 wk. Anti-histone antibodies were generated predominantly to histones H1, H2A, and H2B, a profile different from that observed in NZB/NZW and MRL-lpr/lpr mice. The marked increase in IgG antinuclear antibodies did not correlate with increases in total IgG serum levels and was not associated with comparable increases in antibodies to transferrin, hemoglobin, fibrinogen, or thyroglobulin. Selective autoantibody production was also observed in vitro, wherein GVH spleen cells produced high levels of IgG antibodies to total histones and denatured DNA but not to these non-nuclear protein antigens. In contrast, spleen cells stimulated in vitro with lipopolysaccharide produced equivalent amounts of antibodies to all antigens tested. Our results are in agreement with those of other investigators and collectively suggest that IgG autoantibodies in GVH disease, and possibly in spontaneous lupus-like disease, are not secondary to a generalized B cell activation, but may be selectively generated in response to self antigens with unique configurational properties.     

Production of chemotactic factor for lymphocytes by neutral SH-dependent protease of rabbit PMN leukocytes from immunoglobulins,especially IgM

In inflammation, PMN leukocyte emigration is followed by lymphocyte emigration. Two neutral proteases were isolated from lysosomal fraction of rabbit PMN leukocytes and purified by chromatography. The SH-dependent protease converted in vitro a naturally occurring IgM and specific antibody IgM to a chemotactic factor for lymphocytes; its molecular size was assumed to be around 14,000. Lymphocytes were collected from the thoracic duct lymph of rats. The chemotactic generation was induced by a short treatment with small amount of the enzyme, but the chemotactic factor produced was inactivated by a prolonged digestion with the enzyme. The chemotactic generation by the enzyme of rabbit IgG was apparently less marked. On the other hand, the SH-independent protease was ineffective for such chemotactic generation, suggesting different enzymatic characteristics of these proteases.     

Role of cytotoxic T lymphocytes in the prevention of lupus-like disease occurring in a murine model of graft-vs-host disease

The inoculation of B6D2F1 mice with T lymphocytes from the C57BL/6 parental strain induces an "immunosuppressive" graft-vs-host reaction (B6 GVH), whereas inoculation of T cells from the other, DBA/2 parental strain induces an "immunostimulatory" GVH reaction and a lupus-like disease (DBA GVH). The present study compares cytotoxic T lymphocyte (CTL) function in the spleens of these GVH mice as well as differences in the donor inoculum that could account for these different types of GVH. We observed that the B6 GVH induces an immunodeficiency that encompasses CTL precursors (and possibly T helper cells) and results in suppressor cells that abrogate responses to both trinitrophenyl (TNP)-modified self and third party alloantigens. In contrast, the DBA GVH induces only a T helper cell immunodeficiency and results in suppressor cells selective for class II restricted L3T4+ T helper cells. Chimeric T cells were detected in both types of GVH. In the B6 GVH both L3T4+ and Lyt-2+ donor cells were observed, although Lyt-2+ cells predominated. In the DBA GVH, donor T cells were almost exclusively of the L3T4+ phenotype. The lack of appreciable donor Lyt-2+ cells in the DBA GVH can be explained by a defect in the DBA donor inoculum manifested by a naturally occurring two-fold reduction in Lyt-2+ cell numbers as well as a nine-fold reduction in CTL precursors with anti-F1 specificity. T cells in the DBA inoculum, therefore, are predominantly L3T4+. A similar defect induced in B6 donor cells by anti-Lyt2 antibody and complement not only converted the suppressive GVH to a stimulatory GVH, as measured by anti-DNA antibodies, but also resulted in a T cell immune deficiency characteristic of the DBA GVH, i.e., a selective loss of the TNP-self CTL response. Thus the presence or absence of adequate numbers of functioning Lyt-2+ cells in the donor inoculum is correlated with the development of either a suppressive or stimulatory GVH, respectively. That donor Lyt-2+ cells mediate a suppressive GVH through cytolytic mechanisms is evidenced by greater than 70% reduction in B6 GVH spleen cell numbers and readily demonstrable anti-F1 CTL activity by these spleen cells despite an inability to generate anti-allogeneic or anti-TNP self CTL activity even in the presence of added T helper factors.(ABSTRACT TRUNCATED AT 400 WORDS)