Semiallogeneic Spleen Cells Research Articles

Th2 alloimmunity counteracts Th17-type response in the neonatal establishment of lymphoid chimerism

The neonatal period of life is described as particularly susceptible to develop tolerance. This status of neonatal tolerance has been studied for decades since the discovery that semiallogeneic spleen cells inoculated at birth can induce donor-type graft acceptance. The host neonatal T‑cell compartment that may account for this propensity to develop tolerance is mostly characterized by a Th2-type polarized response and a default in the cytotoxic T lymphocyte (CTL) functions that allow the establishment of lymphoid chimerism and promote donor-type graft survival. We highlighted a new role of alloreactive Th17 cells as a critical barrier to neonatal tolerance that prevents this lymphoid chimerism and further demonstrated that the Th2 immune deviation is essential to control this Th17-type response. We discuss here the potential impact of breaking the tolerizing effects of exposure of the developing offspring to alloantigens in the induction of Th17-type immunity.

Expansion of regulatory CD8+CD25+ T cells after neonatal alloimmunization

Transplantation tolerance induced by neonatal injection of semi-allogeneic spleen cells is associated with a pathological syndrome caused by T helper type 2 (Th2) differentiation of donor-specific CD4(+) T lymphocytes. We have shown previously that this Th2-biased response is inhibited by host CD8(+) T cells. Herein, we demonstrate that upon neonatal immunization with (A/J × BALB/c)F(1) spleen cells, BALB/c mice expand a population of CD8(+) T cells expressing both CD25 and forkhead box P3 (FoxP3) markers. In this setting, CD8(+) CD25(+) T cells predominantly produce interferon (IFN)-γ and interleukin (IL)-10 and are efficient in controlling IL-4, IL-5 and IL-13 production by donor-specific CD4(+) T cells in vitro. CD8(+) FoxP3(-) T cells are single producers of IFN-γ or IL-10, whereas CD8(+) FoxP3(+) T cells are double producers of IFN-γ and IL-10. We further demonstrate that IFN-γ and IL-10 are two major cytokines produced by CD8(+) T cells involved in the in vivo regulation of Th2-type pathology. In this setting, we conclude that neonatal alloimmunization induces the expansion of several regulatory CD8(+) T cells which may control Th2 activities via IFN-γ and IL-10.

366: Novel Lung Preservation with Custodiol N in an Experimental Lung Transplantation Model

semi-allogeneic BALBxC3H spleen (F1/SP, H-2d/k) cells or fully allogeneic BALB fetal liver cells (FLC). The cellular mechanisms responsible for tolerance differ: the former involves alloreactive T-cell deletion and the latter involves induction of non-specific regulatory T-cells. Previous studies suggested that persistent chimerism is important to preserve neonatally-induced tolerance into adulthood. Cellular chimerism can be detected in the F1/SP cell model 3-100 days post-treatment, but only up to 10 days in the FLC model suggesting either that molecular chimerism is responsible for FLC-induced tolerance or that persistent chimerism is not required. This study assessed whether molecular chimerism persists in FLC-treated mice. Methods and Materials: Female C3H neonatal mice were treated with either male F1/SP cells or FLC. Genomic DNA was isolated from various tissues of treated mice at 3 days and 6-8 weeks post-treatment. PCR for the SRY gene was used to detect molecular chimerism. Results: Molecular chimerism was detected in mice treated with F1/SP cells 3 days and 6-8 weeks post-treatment. While molecular chimerism was detected in FLC-treated mice 3 days post-treatment, molecular chimerism could not be detected in any tissues 6-8 weeks post-treatment. Conclusions: These results demonstrate that molecular chimerism is lost prior to adulthood after neonatal FLC treatment, in contrast to F1/SP treatment. Chimerism at molecular and cellular level is thus not required for regulatory neonatal tolerance to donor-specific or thirdparty cardiac allografts. This suggests that induction of non-specific regulatory T-cells occurs early post-injection, and these cells then suppress cardiac rejection and maintain tolerance in adulthood.

Donor bone marrow cells play a role in the prevention of accelerated graft rejection induced by semi-allogeneic spleen cells in transplantation

Spleen or spleen plus bone marrow cells from (BALB/c×C57Bl/6)F1 donors were transferred into BALB/c recipients 21 days before skin or cardiac transplantation. Prolonged graft survival was observed on recipients treated with the mixture of donor-derived cells as compared to those treated with spleen cells alone. We evaluated the expression of CD45RB and CD44 by splenic CD4+ and CD8+ T cells 7 and 21 days after donor cell transfer. The populations of CD8+CD45RBlow and CD8+CD44high cells were significantly decreased in mice pre-treated with donor spleen and bone marrow cells as compared to animals treated with spleen cells only, although these cells expanded in both groups when compared to an earlier time-point. No differences were observed regarding CD4+ T cell population when recipients of donor-derived cells were compared. An enhanced production of IL-10 was observed seven days after transplantation in the supernatants of spleen cell cultures of mice treated with spleen and bone marrow cells. Taken together these data suggest that donor-derived bone marrow cells modulate the sensitization of the recipient by semi-allogeneic spleen cells in part by delaying the generation of activated/memory CD8+ T cells leading to enhanced graft survival.

Deletion of alloreactive cells in neonatal induction of cardiac allograft acceptance by splenocytes VS fetal liver cells

We previously showed that neonatal injection of allogeneic fetal liver cells (FLC) or semi-allogeneic spleen cells (F1SC) induced long-term acceptance of both donor-type and third-party cardiac grafts, however the mechanism remains unclear. In this study, we used as recipients 2C transgenic mice expressing a T cell receptor (TCR) specific for Ld class I MHC antigen to monitor the effects of neonatal treatment with FLC or F1SC.

Neonatal tolerance revisited again: specific CTL priming in mouse neonates exposed to small numbers of semi- or fully allogeneic spleen cells.

Neonatal and adult mice mount distinct responses to allogeneic cells. Injection of neonates with fully allogeneic cells results in lethal graft-vs.-host disease (GVHD), whereas injection of semi-allogeneic (F1) cells leads to lifelong tolerance to the alloantigens, often marked by specific CTL non-responsiveness. In contrast, adults injected with the same number of either cell type become primed and develop vigorous anti-donor CTL activity. One possibility for this differential responsiveness may be developmental immaturity in the CTL arm of the immune system. Recent studies have shown that neonates are capable of mounting mature CTL responses, but only in the presence of strong Th1-promoting agents. Here, we demonstrate that neonates are competent to develop vigorous MHC class I-restricted CTL activity in vivo upon exposure to either fully or semi-allogeneic spleen cells. Specific CTL activity was generated using doses of cells approximately tenfold lower than levels used for the induction of GVHD or tolerance. Thus, the present studies demonstrate that mouse neonates are fully mature in their capacity to develop alloreactive CTL activity, as long as the dose of donor cells is low enough. These results have important implications for the known exposure of human fetuses and infants to small numbers of maternal cells.

CD8+ T lymphocytes regulating Th2 pathology escape neonatal tolerization.

Transplantation tolerance induced by neonatal injection of semiallogeneic spleen cells is associated in several strain combinations with a pathological syndrome caused by Th2 differentiation of donor-specific CD4(+) T lymphocytes. We investigated the role of host CD8(+) T cells in the regulation of this Th2 pathology. IgE serum levels and eosinophilia significantly increased in BALB/c mice neonatally injected with (A/J x BALB/c)F(1) spleen cells when CD8(+) T cells were depleted by administration of anti-CD8 mAb or when beta(2)-microglobulin-deficient mice were used as recipients. In parallel, increased serum levels of IL-5 and IL-13 were measured in blood of tolerant CD8(+) T cell-deficient mice. Whereas neonatally injected mice were unable to generate anti-donor cytotoxic effectors, their CD8(+) T cells were as efficient as control CD8(+) T cells in reducing the severity of Th2 pathology and in restoring donor-specific cytotoxicity in vitro after in vivo transfer in beta(2)-microglobulin-deficient mice. Likewise, CD8(+) T cells from control and tolerant mice equally down-regulated the production of Th2 cytokines by donor-specific CD4(+) T cells in vitro. The regulatory activity of CD8(+) T cells depended on their secretion of IFN-gamma for the control of IL-5 production but not for IL-4 or IL-13. Finally, we found that CD8(+) T cells from 3-day-old mice were already able to down-regulate IL-4, IL-5, and IL-13 production by CD4(+) T cells. We conclude that regulatory CD8(+) T cells controlling Th2 responses are functional in early life and escape neonatal tolerization.

Defects in the regulation of B cell apoptosis are required for the production of citrullinated peptide autoantibodies in mice.

Protein deimination, a process to modify arginine residues to citrulline by the addition of a neutral oxygen group, is associated with apoptosis. The presence of autoantibodies recognizing citrullinated peptides is highly specific to rheumatoid arthritis (RA) and is therefore a useful marker for the early diagnosis of RA. In this study, we explored whether anti-cyclic citrullinated peptide (anti-CCP) autoantibodies are produced in several experimental models of autoimmune diseases in mice. The levels of anti-CCP autoantibodies were analyzed by enzyme-linked immunosorbent assay in several lupus-prone strains of mice, in animals with type II collagen (CII)-induced arthritis, and after induction of neonatal tolerance to alloantigens. We observed the production of these autoantibodies in 2 different lupus-prone mice, MRL-lpr/lpr and (NZW x B6)F(1)-hbcl-2 transgenic mice, characterized by the presence of abnormalities in the regulation of B cell apoptosis. Other genetic defects, determining autoimmune susceptibility, present in MRL and NZW mice were additionally required for anti-CCP autoantibody production. The induction of autoantibodies in normal BALB/c mice injected at birth with semiallogeneic spleen cells from (BALB/c x B6)F(1)-hbcl-2 transgenic mice suggested that these additional autoimmune defects may be related, at least in part, to the establishment of abnormal interactions between T cells and B cells. In addition, anti-CCP autoantibodies were not produced in the course of CII-induced arthritis, an experimental model of RA in mice. Our study provides evidence for the association between defects in the regulatory cell death machinery of B lymphocytes and the production of certain autoantibody specificities.

Lethal host-versus-graft disease and hypereosinophilia in the absence of MHC I-T-cell interactions.

Neonatal injection of semiallogeneic spleen cells in BALB/c mice induces a self-limited state of chimerism that promotes the differentiation of donor-specific CD4 T cells toward the Th2 phenotype. Here we show that injection of spleen cells from beta2-microglobulin-deficient (BALB/c x C57BL/6) F1 mice into BALB/c newborns with a disrupted beta2-microglobulin (beta2m) gene results in a lethal lymphoproliferative disorder associated with uncontrolled Th2 response, long-term persistence of donor B cells, and sustained blood eosinophilia. Autoimmune manifestations are also enhanced and characterized by a severe autoantibody-mediated glomerulonephritis. Histological examination of the spleen shows a hyperplasia of periarteriolar lymphoid sheaths, with accumulation of eosinophils and basophils, and variable degree of fibrosis. Perivascular lymphoid infiltrates with eosinophils are also found in the lung and are correlated with disease severity. Such abnormalities are almost absent using beta2m-sufficient mice. These data demonstrate that induction of lymphoid chimerism in the absence of MHC class I-T-cell interactions results in a lethal form of host-versus-graft disease that represents a unique model of Th2-dependent chronic inflammatory disease associated with an hypereosinophilic syndrome in mice.

ALLOANTIGEN-UNRESPONSIVENESS IS ASSOCIATED WITH EARLY TCR SIGNALING DEFECTS IN VIVO

667 Intracellular signaling events that result in T cell unresponsiveness have recently been described in vitro. Studies of in vivo tolerance have been limited by the requirement for large numbers of clonally specific T cells. A detailed understanding of the biochemical events that occur in vivo after alloantigen recognition by T cells is however crucial for the future development of selective interventions modulating T cell activation in organ transplantation. To elucidate changes in intracellular signaling that characterize tolerancein vivo, we took advantage of mutant mice that express an alloantigen-specific TCR, 2C, as a transgene in >95% of peripheral T cells. The 2C TCR is restricted to Ld, a class I MHC molecule expressed in BALB/c mice. We have previously shown that 2C mice are extremely alloreactivein vitro and in vivo to BALB/c. We have also shown that the allorecognition is specific to the naturally occurring allopeptide p2Ca and the class I MHC molecule Ld. 2C mice transplanted with a vascularized BALB/c cardiac graft activate a sufficient number of T cells for biochemical analysis in vivo. Our current studies demonstrate that 2C mice can be rendered tolerant of vascularized BALB/c (H-2d) cardiac heart grafts. InFig 1., control, unmanipulated, 2C mice reject BALB/c cardiac grafts in 5-8 days whereas injection with semiallogeneic spleen cells (tolerized) confers alloantigen-specific tolerance. The tolerized state is long-lasting and associated with diminished in vitro alloresponsiveness.These tolerized mice show marked differences in early TCR-mediated signaling events compared to naive mice. Specifically, ZAP-70 phosphorylation is absent and Lck activity is diminished. The defects appear to be restricted to specific TCR-mediated signal transduction pathways as other proteins analyzed remain competent for signal transduction. We believe this is the first example of TCR-mediated signaling defects associated with in vivo alloantigen-specific tolerance.

Host H-2 haplotype modulates the induction of host-versus-graft disease after the induction of neonatal tolerance to H-2 alloantigens.

Mice injected at birth with semiallogeneic spleen cells develop a host-versus-graft disease (HVGD) characterized by the polyclonal activation of donor B cells by alloreactive host CD4+ T cells, the production of autoantibodies (autoAb) and the development of an inmmunocomplex-mediated glomerulonephritis. It has been demonstrated that the recognition of MHC class II, but not class I or non MHC, alloantigens triggers the development of the autoimmune syndrome (AIS). The finding of different expression patterns of Ia molecules in different mouse strains, and a closed restriction of some immune responses to particular H-2 haplotypes, prompted us to analyze whether variations in the expressed MHC class II molecules modify the HVGD. First, newborn BALB/c mice received spleen cells from F1 hybrid mice obtained by mating BALB/c mice with several mouse strains differing in the H-2 haplotype. Second, spleen cells from different F1 mice were neonatally injected in mice of both parental strains. All groups of BALB/c mice injected with different combinations of F1 mice showed an HVGD with a very similar serological course. However, in some instances, duration was different when comparing both parental strains injected with spleen cells from the mutual F1 hybrids. These results suggest that host MHC, but not donor MHC haplotype may modulate the AIS associated with the induction of neonatal tolerance.

Completely allogeneic spleen cells induced cytolytic neonatal tolerance to alloantigens, but failed to establish allo-helper interactions with host T cells.

The injection of spleen cells from F1 mice into-newborns from a parental strain results in the establishment of cytolytic tolerance to donor alloantigens and the development of a lupus-like disease. This syndrome is the consequence of the recognition by alloreactive host CD4+ T cells of discordant major histocompatibility complex (MHC) class II antigens on semi-allogeneic donor B cells. We have analysed whether completely allogeneic spleen cells are as able as semi-allogeneic spleen cells to induce cytolytic tolerance to donor alloantigens and to co-operate with alloreactive T cells for autoantibody production. BALB/c mice were injected at birth with Thy-1-depleted spleen cells from (C57BL/6 x BALB/c)F1 or C57BL/6 mice, either alone or in combination. Cytolytic tolerance was always induced, as manifested by persistence of chimerism and acceptance of skin allografts. However, only F1 semi-allogeneic B cells were activated by alloreactive host T cells to produce anti-DNA IgG antibody. The deficient co-operation between BALB/c CD4+ T cells and completely allogeneic C57BL/6 B cells was confirmed after neonatal injection of (C57BL/ 6 x BALB/c)F1(Igha) spleen cells together with C57BL/6(Ighb) spleen cells. These mice developed anti-DNA antibodies bearing only the Igha allotype. Similar results were observed in experiments of allogeneic interaction in vitro, in which BALB/c CD4+ T cells were cocultured with either (C57BL/6 x BALB/c)F1 or C57BL/6 B cells. The present results demonstrate that completely allogeneic spleen cells efficiently induced cytolytic unresponsiveness to donor alloantigens, but B cells contained in this spleen cell population were unable to establish allo-helper interactions with alloreactive CD4+ T cells, suggesting that cytolytic and helper T-cell interactions involved in alloreactivity may be different.

Altered serum cytokines in hepatic and portal blood of rats at early times following portal venous infusion of semi-allogeneic cells

The liver of anaesthetized adult (>350 g) Lewis rats was perfused in vitro after cannulation of both the hepatic and portal vein, with clamping of the hepatic artery. Heparinized blood (400 μl) was withdrawn at 0, 6, 12, 18, 24, 30 and 36 h from each site, and serum and peripheral blood lymphocytes (PBL) isolated after ficoll/hypaque separation. Serum was tested in bioassays for cytokines known to modulate lymphocyte:endothelial interactions in vivo and in vitro (IFNγ, TGFβ, TNFα, IL-6, IL-1). In some experiments rats received, via portal venous infusion, a sterile inoculum of 150 × 10 6 semi-allogeneic (LBN F 1) spleen cells immediately or 12 h after the start of the study. In animals which were unchallenged with cells via the portal vein, subtle differences in detectable cytokines were observed between hepatic and portal blood samples, as reported in earlier studies. Within 12 h the minor perturbations observed in cytokine profiles following surgical insult resolved, and the changes between hepatic and portal venous samples remained constant throughout the study in control rats. However, in rats treated with LBNF 1 cells, changes in the cytokine profiles were seen compared with control animals, and as a function of time post F 1 cell infusion. Changes in mRNAs for different cytokines were observed in PBL taken from portal/hepatic blood in these same animals. These data point to one possible mechanism whereby the liver may influence immunological processes following portal venous antigen challenge.

Autoimmunity Following Neonatal Tolerance to Alloantigens: Role of Donor I-A and I-E Molecules

The injection of semi-allogeneic F1 spleen cells into newborn mice of a parental strain induces a state of immune tolerance characterized by anti-donor CTL unresponsiveness and the appearance of a transient SLE-like autoimmune syndrome associating autoantibody production, hypergammaglobulinemia, splenomegaly and glomerulonephritis. Our previous experiments have demonstrated that host Th2-like CD4+ T lymphocytes activate donor F1 B cells persisting in the host to produce autoantibodies, and that this cellular interaction relies on the presence of alloMHC class II molecules on donor B cells. In order to investigate the role and the involvement of MHC alloantigens in the cellular T(host)-B(donor) interaction, newborn C57BL/6 (B6) mice were injected with F1 spleen cells differing from the host at the level of defined portions of the MHC class I (K) or class II (I-A and I-E) molecules. B6 mice injected at birth with spleen cells from different F1 strains were tolerant to each alloantigen (alloAg) tested, as assessed by specific anti-donor CTL unresponsiveness. However, the SLE-like autoimmune syndrome only developed in B6 mice injected at birth with F1 spleen cells differing at the level of MHC class II I-A or I-E molecules. Autoantibodies appeared later in B6 mice neonatally tolerized to I-E alloAg than those detected in B6 mice neonatally tolerized to I-A alloAg. These results show that the SLE-like autoimmune disease that develops concomitantly to neonatally-induced tolerance to alloAg is the consequence of cognate T host-B donor cellular interactions triggered by even minute differences in the MHC class II I-A or MHC class II I-E molecules.

IFN-gamma prevents Th2 cell-mediated pathology after neonatal injection of semiallogenic spleen cells in mice.

Abstract BALB/c mice injected at birth with 10(8) (A/J X BALB/c)F1 hybrid spleen cells develop an autoimmune host-vs-graft (HVG) disease as a result of activation of donor B cells by host CD4+ cells. The antidonor CD4+ cells seem to be Th2-like cells, inasmuch as they are profoundly deficient in IL-2 and IFN-gamma production, but secrete high levels of IL-4 and IL-10. As IFN-gamma is known to inhibit the development of TH2 cells, we attempted to modulate HVG disease by injecting rIFN-gamma. First, we found that 10 micrograms of rIFN-gamma given on days 1 and 3 after birth reduced the serum hyper-IgE of HVG mice by 90% and the serum hyper-IgG1, by 70%. In addition, rIFN-gamma administration significantly decreased the anti-DNA IgG1 titers and prevented the occurrence of anti-glomerular basement membrane and anti-laminin IgG1 Abs as well as the formation of immune deposits in renal glomeruli. These effects were not caused by the abrogation of chimerism, as indicated by the persistence of donor-type B cells in lymph nodes and of Igs bearing donor allotype in serum. MLC experiments indicated that the major effect of early rIFN-gamma administration was to restore the production of IL-2 and IFN-gamma by donor-specific T cells while these cells still secreted significant amounts of IL-4 and IL-10. Unresponsiveness of antidonor cytolytic T cells was not influenced by rIFN-gamma. We conclude that rIFN-gamma prevents the TH2-type response induced by the neonatal injection of semiallogeneic spleen cells and the associated pathology.

Autoimmunity, hyporeactivity to T cell mitogens and lymphoproliferative disorders following neonatal induction of transplantation tolerance in mice

We have reported that, in A/J (A) (H-2a) mice, a partial tolerance to C57BL/10ScSn (B10) (H-2b) skin allografts and a high incidence of lethal lymphoproliferative disorders (LPD) can be induced by the neonatal i.v. injection of 2 x 10(7) semiallogeneic (B10 x A)F1 spleen cells (SC) (Végh, P., Baranyi, L. and Jánossy, T., Cell. Immunol. 1990, 129: 56). In this study, we show that the incidence and mortality of LPD were continuously growing from 1 month of age until the end of the experiment at 1 year (64% and 36%, respectively). Based on histology, 27% of the diseased mice suffered from lymphoid malignancies. In the remaining cases (73%), reactive histopathological changes were seen in the spleen, lymph nodes (LN), liver and kidneys. The proportion of CD4+ T cells in the spleen and LN as well as that of splenic B cells decreased, while the percentages of mature and immature myeloid cells doubled. The total cell number of each (sub)population, however, was elevated in both lymphoid organs. The cells taking part in the lymphoproliferation were of host (A) and not of donor (F1) origin. Preceding the development of apparent LPD, the SC, LN cell and thymus cell suspensions of 1-month-old tolerized mice showed reduced in vitro proliferative responses to T cell and T cell-dependent B cell mitogens (Con A or PWM), while their reactivity to a T cell-independent B cell mitogen (lipopolysaccharide) was essentially unimpaired. This hyporeactivity seems to be functional, because neither histology nor immunophenotyping by flow cytometry revealed significant alterations in the spleen and thymus of such animals, apart from a slight reduction in the ratio of CD4+/CD8+ T cell subpopulations in the spleen. The in vivo T cell-mediated immune response of the tolerized mice was practically normal to third party CBA/Ca (H-2k) allografts. Antithymocyte autoantibodies (ATA) were detected in the sera of 76% of the tolerized mice at 1 month of age (i.e., even before the mass appearance of LPD). ATA as well as antinuclear Ab were present in 65% of the adult tolerized mice, independently of the presence of LPD. Taken together, in A mice neonatally injected with (B10 x A)F1 SC, a partial, specific allograft tolerance and a chronic host-vs.-graft disease-like syndrome developed. The latter is manifested in hyporeactivity to T cell mitogens, development of autoantibodies and, subsequently, in progressive LPD and lymphoid malignancies.

Characterization of host CD4+ T lymphocytes in mice neonatally tolerized to alloantigens.

BALB/c mice injected at birth with semi-allogeneic F1 spleen cells become tolerant to alloantigens as shown by their CTL unresponsiveness to the corresponding alloantigen and the persistence of donor F1 cells into the BALB/c host. Moreover, these mice develop a transient systemic lupus erythematosis-like autoimmune syndrome characterized by splenomegaly, glomerulonephritis, thrombocytopenia and abnormal serological findings, such as several autoantibodies and IgG1 hypergammaglobulinemia. Recent studies done in our laboratory have shown that donor F1 B cells persisting in the host are responsible for the production of autoantibodies and must be activated in vivo by the host CD4+ T lymphocytes in a MHC class II-restricted fashion. In the present work, we have focused our attention on the ability of splenic CD4+ T cells recovered at different periods from BALB/c mice injected at birth with (CBA/Ca x BALB.Ighb) F1 spleen cells to interact with and activate F1 semi-allogeneic spleen cells in vitro. We show that (i) only CD4+ T cells from 2- and 3-week-old tolerant BALB/c mice preferentially produce IL-4 and IL-5 in response to a F1 semi-allogeneic in vitro stimulation, (ii) CD4+ T cells purified from 3-week-old tolerant BALB/c mice are able to induce in vitro IgG and IgM production by F1 B cells. Taken together, these results strongly suggest that host CD4+ T cells, belonging to the TH2 subset progressively lose their reactivity towards the F1 semi-allogeneic persistent B cells, reaching a state of unresponsiveness that correlates with the disappearance of serum autoantibodies and autoimmune pathology.

Autoimmune syndrome after induction of neonatal tolerance to I‐E antigens

Neonatal injection of semiallogeneic spleen cells induces a state of specific tolerance to the parental alloantigens, but also the development of an autoimmune syndrome known as host-versus-graft disease (HVGD). The autoimmune features are a consequence of the allogeneic cooperation between persisting alloreactive host T helper type 2 (TH2) cells and donor semiallogeneic B cells. It has been established that I-A alloantigens play a central role in the triggering of this HVGD. Here it was investigated if I-E antigens, which have shown functional differences, regarding autoimmunity and alloreactivity, with respect to I-A antigens, are also able to trigger this autoimmune syndrome. The injection of spleen cells from [B10.A(4R) x B10.A(2R)]F1 (I-E+) hybrid mice into newborn B10.A(4R) (I-E-) mice was accompanied by the establishment of chimerism and also by the development of a characteristic, but moderated, HVGD. The weak intensity of this HVGD is likely due to the moderation of the alloreactive responses induced against I-E molecules. Moreover, the marked increase in the levels of IgE and in the titers of anti-DNA IgG1 antibodies strongly suggest that alloreactive TH2 cells play also a main role in the autoimmune syndrome following tolerization to I-E antigens. Therefore, it is concluded that the I-E and I-A isotypes are functionally similar with respect to the allogeneic cellular interactions that account for the HVGD.

Anti-Ia Treatment Prevents Lupus-like Autoimmune Syndrome in Mice Neonatally Tolerized to Alloantigens

Neonatal injection of semi-allogeneic F1 spleen cells into newborn parental mice results in induction of tolerance to the corresponding class I alloantigen and chimerism. This state of tolerance is associated with the development of a transient lupus-like autoimmune syndrome. Previous experiments performed in our laboratories have shown that host CD4+ T lymphocytes and donor B cells persist in the host and are essential in triggering the autoimmune syndrome observed in neonatally tolerized mice. In this study, we show that early treatment of tolerized mice with anti-donor MHC class II mAb totally prevents the lupus-like syndrome. Moreover, delayed treatment significantly decreases, but to a lesser extent, autoimmune pathological features in tolerized mice. Taken together, these results show that lupus-like autoimmune syndrome developed by neonatally tolerized mice is efficiently prevented by anti-Ia treatment without interfering with the induction of tolerance.

Susceptibility and resistance to autoimmunity following neonatal injection of semi-allogeneic spleen cells in rats

A model of neonatal allotolerance was developed in rats. Brown-Norway (BN) neonates injected with semi-allogeneic (BN × Lewis) F1 hybrid spleen cells express a long-lasting chimerism and exhibit polyclonal B cell activation demonstrated by hyperimmunoglobulinemia affecting mainly IgE and IgG1, anti-laminin and anti-DNA autoantibodies as well as glomerulonephritis and anti-hapten antibodies. These abnormalities are autoregulated although the chimerism persists. In contrast, Lewis (LEW) neonates injected with semi-allogeneic (BN × LEW) F1 hybrid spleen cells exhibit a very short-lasting chimerism and transient activation of B cells, as reflected by increased allo-class II antigen expression, but do not develop an autoimmune disease. The autoimmune syndrome observed in BN rats is similar to that reported in mice during host-versus-graft reaction. Similarities between the drug-induced models of autoimmunity and allogeneic reactions in BN rats are also striking. The susceptibility of BN rats and the resistance of LEW rats to these autoimmune diseases might respectively reflect the involvement of TH2-like or of TH1-like subsets.