Donor Spleen Cells Research Articles

Donor-specific immunological non-responsiveness after liver transplantation

Abstract Since the rate of immunological losses of liver allograft after the immediate posttransplant period is much lower than in other organs, we studied the immune responses against donor HLA antigens in 18 patients with a good long-term outcome to determine whether the development of a state of immunological non-responsiveness to donor antigens might account for this favorable outcome. The reactivity against donor spleen cells was measured before and 2 years after transplantation. The reactivity in mixed lymphocyte culture (MLC) and the frequencies of cytotoxic T cell precursors (CTLp) were determined. Responses against thirD-party spleen cells were determined concurrently to exclude a generalized reduction of immunocompetence due to chronic immunosuppressive treatment. Before orthotopic liver transplantation, the majority of patients had normal T cell responses against donor antigens that were comparable to those against thirD-party antigens. Two years after transplantation, donor-specific MLC non-reactivity had developed in 10 of the 18 (56%) patients. In addition, 15 of 18 (83%) patients had developed donor-specific cytotoxic Tcell (CTL) non-responsiveness; 2 had reduced numbers of CTLp against both donor and thirD-party cells, while the remaining patient had maintained reactivity against donor antigens. In conclusion, donor-specific non-responsiveness is present in the majority of patients 2 years after successful liver transplantation, but occurs predominantly at the CTL level.

MODULATION OF HEME OXYGENASE (HSP-32) BY COBALT-PROTOPORPHYRIN ABROGATES DEVELOPMENT OF ACUTE GVHD IN A PARENT TO F1 MOUSE MODEL

637 Graft versus host disease (GVHD) remains a significant cause of morbidity and mortality after bone marrow transplantation. Recently, we demonstrated that elevated expression of heme oxygenase-1 (HO-1 or Hsp-32), an enzyme responsible for the degradation of hemoglobin to biliverdin and carbon-monoxide, results in the modulation of several immune effector functions. Based on these observations we evaluated if Cobalt-protoporphyrin(CoPP), a compound well known to induce HO-1 expression can prevent the development of acute GVHD. Acute GVHD was initiated by injection of unfractionated spleen cells from C57BL/6 into B6D2/F1 mice. Subsequently, recipients were given a single intravenous injection of saline or CoPP at 2.5 or 5 mg/kg. Administration of CoPP resulted in increased survival: 85% of CoPP treated animals (6 out of 7) survived for more than 30 days compared to only 29% of control animals (2 out of 7, p < 0.1). To determine if the protective effect of CoPP therapy was due to immunomodulation of the recipient or the donor cells, donor mice were treated with different doses of CoPP three days before harvesting their spleen cells. 80% of recipients (4 out of 5) injected with spleen cells from CoPP-treated donors (20 mg/kg) survived for more than 100 days compared to none of the mice (0 out of 5) injected with spleen cells from vehicle treated donors. No significant weight change was observed in animals injected with spleen cells from CoPP treated animals. The immunocompetence of injected animals was assessed on days 2, 15 and 100. Two days after injection of vehicle-treated donor-spleen cells, an increased spontaneous proliferation of lymphocytes could be measured in vitro. Such proliferation was not seen with recipients injected with CoPP-treated donor-spleen cells. Cytokine analysis revealed elevated IFN-γ production by spleen cells isolated from mice with GVHD, while spleen cells isolated from protected recipients secreted significantly lower levels of IFN-γ. Mice with active GVHD demonstrated a defective lymphoproliferative response to alloantigens or ConA. However, spleen cells isolated from survivors (on day 100) responded normally. Furthermore, anti-host cytotoxic T cell activity was reduced in protected mice compared to mice with GVHD. Flow cytometric analysis of splenic T cell populations revealed a majority of donor type (H2b+) cells in mice with active GVHD versus a majority of recipient (H2b+, H2d+) cells in protected mice on day 45. On day 100, the spleen cell population of three out of four (75%) long-term survivors showed a normal recipient phenotype. In conclusion, results from confirmed our previous observations that upregulation of HO-1 activity is associated with down-regulation of certain immune effector functions. This results in protection from acute GVHD in a parent into F1 mouse model.

EFFECTS OF SELECTIVE CD28-B7-1 BLOCKADE IN ACUTE CARDIAC ALLOGRAFT REJECTION

99 CTLA4Ig is a molecule that inhibits the CD28:B7 costimulation pathway by binding to both known forms of B7, B7-1 and B7-2. This compound has been shown to induce permanent graft acceptance in a number of transplant models. It has been suggested that both B7-1 and B7-2 may have different roles with regard to their signaling functions, and signaling through either ligand alone may lead to alternate immune responses. We are now studying the effects and mechanisms of selective B7-1 blockade in a fully allogeneic cardiac transplant model in vivo. LEW rats were challenged with WF cardiac allografts. Treatment with a single dose of 0.5 mg of CTLA4Ig + DST (4×107 donor spleen cells iv.) at the time of engraftment induces permanent graft acceptance in 50% of the recipients (n=12). In the same protocol, administration of Y100F, a "mutant" form of CTLA4Ig, which selectively binds to B7-1 but spares B7-2, could not prevent acute allograft rejection (MST 10.3±2.3 days, n=6). Control animals typically reject their grafts within seven days. Cellular and humoral immune responses were assessed in cardiac allograft recipients receiving CTLA4g or Y100F in conjunction with DST. On day 7 after engraftment, the mixed-lymphocyte-response revealed minimal donor-specific reactivity in CTLA4Ig treated animals (Relative Response: 0.05 against WF, 0.4 against BN) compared to unmodified rejecting controls. In contrast, lymphocytes from Y100F treated animals proliferated significantly against donor cells (Relative Response: 0.4 against WF, 0.7 against BN). Although reduced when compared to controls (39.1% lysis), an anti-donor cytotoxic-T-lymphocyte generation (CTL) response in Y100F treated animals was detectable (17.8% lysis), while donor-specific cytotoxicity was almost completely abrogated in CTLA4Ig treated animals (7.4% lysis). CTLA4Ig treatment prevented the development of significant donor-specific IgM and IgG allo-antibody responses, whereas Y100F treated recipients as well as unmodified rejecting controls developed significant IgM and IgG allo-antibodies at the timepoint of graft loss. These data indicate that the selective blockade of B7-1 alone is not sufficient to abrogate cellular and humoral immune responses leading to acute allograft rejection. The combined blockade of B7-1 and B7-2 is necessary to direct the immune response towards hyporesponsiveness and promote long term graft acceptance.

Cellular immune responses of human cadaver donor bone marrow cells and their susceptibility to commonly used immunosuppressive drugs in transplantation.

The cascade of immunological effects brought about by donor bone marrow cell (DBMC) infusions in human organ transplantation, especially in the context of continuous pharmacologic immunosuppression, is not fully understood. Yet, in inbred rodents and even primates, administration of specific bone marrow cells has caused a state of acquired immunologic tolerance. In vitro mixed lymphocyte culture (MLC) and cell-mediated lympholysis (CML) culture systems were used to compare the responding and regulatory properties of DBMC and individual bone marrow cell subsets versus spleen cells in the presence or absence of pharmacologic immunosuppression. In the absence of immunosuppressive drugs, the DBMC proliferated in MLC and in response to phytohemagglutinin, but to a lower magnitude than donor spleen cells. In CML assays, DBMC failed to function as cytotoxic cells. Removal of both CD3+ and CD34+ cells together (not just singly) had to occur for complete abrogation of the proliferative response of DBMC evoked in the presence of allogeneic stimulating cells. Testing several experimental variables using flow cytometric analysis led to the conclusion that when purified DBMC CD34+ cells were placed in coculture with irradiated allogeneic peripheral blood mononuclear cells, such CD34+ cells give rise both to CD3- TCRalphabeta+ as well as to dimly staining CD3+ TCRalphabeta+ cells. Low pharmacologic concentrations of tacrolimus/cyclosporine (CsA) and mycophenolic acid (MPA) singly or in combination had no effect on the spontaneous proliferation of DBMC and had significantly less inhibitory activity on MLC responses of DBMC and its purified CD3+ or CD34+ subpopulations, compared with the responses of spleen cells. Moreover, the previously described regulatory effects of DBMC on the MLC responses of peripheral blood or splenic responding cells were not inhibited by these immunosuppressive drugs. Taken together, these results support the notion that in vitro DBMC subpopulations, which proliferate as responding cells in co-culture with x-irradiated allogeneic cells and which cause regulatory effects when added as a third component to MLC reactions, seem to be culture-generated lymphoid cell lineage(s) progeny of CD34+ cells. This possibly includes unique CD3+ "primitive" (dimly staining) T cells, which are not as inhibited in their function by tacrolimus/CsA and MPA, as are postthymic (splenic) T cells.

A fetal sheep liver extract reverses age-related increments in spontaneous and induced cytokine production by indirect environmental effects

BALB/c, DBA/2 and C57BL/6 mice of different ages (ranging from 8 to 110 weeks of age) were used as spleen cell donors to assay cytokine production from ConA activated spleen and Peyer's Patch (PP) lymphocytes. As reported in an earlier publication, there was an age-related decline in IL-2 production in all strains, with a general increase in IL-4 and IL-10 production with age, this being particularly marked for PP cell preparations. Similar conclusions were reached from independent analysis of CD44 hi and CD44 lo cell populations in these groups (memory vs. naive cells, respectively). Interestingly, IL-6 production was dramatically increased (some 4–5-fold in the different strains) and significantly increased levels of IL-6 were detected in the serum of aged mice. A previously described sheep fetal liver extract was able to reverse, to varying degrees, these cytokine changes associated with aging. Interestingly, when cells from aged mice were adoptively transferred to lethally irradiated young (8 week) recipients, the cytokine production phenotype of cells harvested from recipient mice 3 weeks later was that of the aged donor, unless recipients were treated continually with extract. Treatment of the donor alone produced minima1 changes in cytokine production 3 weeks following adoptive transfer. The effect of extract was reversed in treated aged mice by concomitant daily intravenous infusion of the competitive inhibitor of nitric oxide synthesis (NG-monomethyl- l-arginine (NMMA)), which also decreased the increased serum nitrate levels in mice treated with extract. Our data suggest an important role for reactive nitrogen products, themselves induced by fetal liver extract, in age-associated changes in cytokine production.

Microchimerism and hyporesponsiveness induced by intraportal injection of donor spleen cells in rats

It is controversial whether or not microchimerism (MC) is responsible for the induction and maintenance of donor-specific tolerance. We have shown that intraportal injection (i.p.) of donor splenocytes induces a long-term graft survival of liver and heart in rats. In this study, we examined by polymerase chain reaction (PCR) the status of MC in the liver, spleen, and blood of rat cardiac recipients following i.p. or intravenous injection (i.v.) of donor splenocytes. Male DA (RT1 a) and Wistar (RT1 k) rats were used as donors and recipients, respectively. Heterotopic heart transplantation was performed 10 days after i.p. or i.v. injection of 5 × 10 7 DA spleen cells. DA cardiac allografts were rejected with a mean survival time (MST) of 11.9 ± 1.6 ( n = 10) days in nontreated recipients. Injections (i.v.) led to no significant prolongation of graft survival (MST: 11.2 ± 1.9 days, n = 6), while i.p. injection induced a significant prolongation of graft survival (MST: 18.6 ± 1.5 days, n = 5) over the control. Either i.p. or i.v. injection alone resulted in systemic MC in these organs throughout the observation time over 60 days. MC was detected in the spleen, liver, and blood of cardiac recipients 7 days after transplantation and also even after cessation of cardiac heartbeat 21 days after transplantation. This was the case with either i.p. or i.v. group, which showed MC on day 7 after transplantation and persistent MC after cessation of the heartbeat. These data suggest that the presence of MC in the liver, spleen, and the blood of transplant recipients may not be responsible for immunological unresponsiveness to donor antigens.

Microchimerism and hyporesponsiveness induced by intraportal injection of donor spleen cells in rats.

It is controversial whether or not microchimerism (MC) is responsible for the induction and maintenance of donor-specific tolerance. We have shown that intraportal injection (i.p.) of donor splenocytes induces a long-term graft survival of liver and heart in rats. In this study, we examined by polymerase chain reaction (PCR) the status of MC in the liver, spleen, and blood of rat cardiac recipients following i.p. or intravenous injection (i.v.) of donor splenocytes. Male DA (RT1a) and Wistar (RT1k) rats were used as donors and recipients, respectively. Heterotopic heart transplantation was performed 10 days after i.p. or i.v. injection of 5 x 10(7) DA spleen cells. DA cardiac allografts were rejected with a mean survival time (MST) of 11.9 +/- 1.6 (n = 10) days in nontreated recipients. Injections (i.v.) led to no significant prolongation of graft survival (MST: 11.2 +/- 1.9 days, n = 6), while i.p. or i.v. injection alone resulted in significant MC in these organs throughout the observation time over 60 days. MC was detected in the spleen, liver, and blood of cardiac recipients 7 days after transplantation and also even after cessation of cardiac heartbeat 21 days after transplantation. This was the case with either i.p. or i.v. group, which showed MC on day 7 after transplantation and persistent MC after cessation of the heartbeat. These data suggests that the presence of MC in the liver, spleen and blood of transplant recipients may not be responsible for immunological unresponsiveness to donor antigens.

Increased rejection of murine allogeneic bone marrow in presensitized recipients.

The role of presensitizing murine recipients with donor spleen cells prior to T cell-depleted or -repleted H-2 compatible allogeneic bone marrow transplantation (BMT) was investigated at two different doses of total body irradiation (TBI). Recipients that were presensitized with 2 x 10(7) irradiated donor spleen cells at 1 week before a sublethal dose of 6 Gy TBI and BMT showed no evidence of donor blood chimerism while unsensitized recipients showed about 80% donor engraftment as determined by blood Gpi phenotyping. After raising the TBI dose to 9.5 Gy an increase in mortality from marrow failure was observed in presensitized animals. No significant engraftment-promoting effect of up to 2 x 10(6) T cells (20% of total marrow dose) was seen either in presensitized or unsensitized mice. It can be concluded that presensitized recipients are more susceptible to acute marrow rejection and that T cells added to the bone marrow did not influence the level of donor engraftment in these recipients.

TNF receptor p55 controls early acute graft-versus-host disease.

Allogeneic bone marrow transplantation is frequently associated with graft-vs-host disease (GVHD). To understand the effector mechanisms of GVHD, we investigated the role of the TNF receptor p55 (TNFRp55), which is known to be important in inflammation and cytotoxicity. After the transplantation of allogeneic bone marrow and spleen cells to lethally irradiated mice, all wild-type recipients developed early lethal GVHD within 1 wk, whereas TNFRp55-deficient recipients had much reduced GVHD and survived for at least 3 wk. No defect in alloantigen presentation was found, since T cell proliferation and cytotoxicity were similar to allogeneic wild-type and TNFRp55-deficient stimulator and target cells. Also, TNF alpha release did not differ significantly between the two types of recipients. Therefore, early acute GVHD in wild-type mice was primarily due to TNFRp55-mediated tissue damage. Interestingly, lethal GVHD was not entirely dependent upon the TNFRp55. In experimental conditions using sublethal irradiation and high donor spleen cell numbers, TNFRp55-deficient recipient mice developed lethal GVHD with similar kinetics and frequency as the control mice. These data suggest that the effector mechanisms leading to organ damage in murine acute GVHD can be dissected in a cytokine pathway through the TNFRp55, as demonstrated here, and in a cellular pathway through direct interaction of cytotoxic lymphocytes with target tissues involving perforin and Fas/Fas ligand, as reported previously.

Experimental Hepatitis in Neonatally Thymectomized Mice: Transfer of Disease and the Role of T Cells

Using neonatally A/J thymectomized mice, we have produced chronic hepatitis by administration of sublethal doses ofPropionibacterium acnesand lipopolysaccharide (LPS). Our goal in this unique model was to evaluate the effector cell population required to generate chronic hepatitis by transferring spleen cells or splenic subpopulations derived from donor thymectomized mice with chronic hepatitis into congenic recipient nonimmunized thymectomized or sham-thymectomized animals. Several key observations were made regarding the ability to induce and to transfer disease. First, an inflammatory liver injury in neonatally thymectomized (NTx) mice was readily generated using sublethal doses ofP. acnesand LPS. Second, the lesions were persistent and associated with the production of autoantibodies to liver-specific lipoprotein and anti-nuclear antibodies. Third, these features were not found in comparably injected nonthymectomized control A/J mice. Fourth, the same liver injury was transferred to neonatally thymectomized but otherwise naive mice by the transfer of donor spleen cells from affected mice previously induced to develop experimental hepatitis. Fifth, the transfer of this liver injury could not be achieved using T-cell-depleted spleen cells. Deletion of CD4+T cells or CD8+T cells by sensitized spleen cells resulted in suppression of the transferred liver injury. In contrast, transfer of nylon wool adherent splenic T cells induced severe hepatitis. These data suggest that the chronic liver injury induced in NTx mice by administration ofP. acnesand LPS involves a breakdown in tolerance accompanied by the appearance of autoantibodies and that nylon wool adherent CD4+and CD8+T cells play important roles in the modulation of liver injury.

Pancreas and kidney allograft-infiltrating cells in simultaneous pancreas-kidney transplantation.

Rejection after pancreas-kidney transplantation may occur isolated or concurrently in both grafts. To get more insight into the cellular mechanisms underlying these rejection episodes, we compared the functional characteristics of pancreas and kidney graft-infiltrating T cells. Graft-infiltrating T cell (GIC) lines were cultured from simultaneously taken pancreas and kidney biopsies from eight patients. CD4 to CD8 ratios were determined by fluorescence-activated cell sorter and cytotoxicity toward donor proximal tubular epithelial cells (PTEC) and donor spleen cells (DSC) using a standard cytotoxicity assay. Cytokine production was determined by enzyme-linked immunosorbent assay. CD4 to CD8 ratios were comparable between the pancreas and kidney lines for each patient, but differences were observed in cytotoxicity toward PTEC and DSC. For four of eight patients, the lysis of PTEC by pancreas GIC was less than the lysis induced by kidney GIC. This was also seen in three of five patients for lysis of DSC. The specificity of GIC lines toward mismatched donor antigens was studied for two patients and appeared to be comparable for pancreas and kidney. Most GIC lines produced interferon (IFN)-gamma (75.5+/-22.7 pg/ml), but no IL-10, indicating that the cell lines consisted primarily of Th1 and type 1 CD8+ cells. Mean production of IL-6 was 465.6+/-193.6 pg/ml. No major differences were observed between kidney and pancreas GIC for either cytokine. We conclude that pancreas and kidney GIC lines have the same phenotype, cytokine production, and allospecificity. Differences were, however, seen for lysis of PTEC and DSC, suggesting that tissue-specific antigens might play a role.

Modulatory effects of human donor bone marrow cells on allogeneic cellular immune responses.

In order to evaluate whether immunoregulatory mechanisms are brought about by human donor bone marrow cell infusions accompanying organ transplantation, we established in vitro culture systems analogous to the transplant model. Cell-mediated lympholysis (CML) and mixed lymphocyte culture (MLC) responses of peripheral blood lymphocytes or spleen cells stimulated with irradiated cadaver donor spleen cells in the presence of specific donor vertebral-body bone marrow cell (DBMC) modulators were tested. When compared with spleen cells as modulator controls, DBMC inhibited both the proliferative and cytotoxic responses in a dose-dependent manner. Use of unirradiated and T cell-depleted DBMC was required for detection of the inhibitory activity. Furthermore, DBMC had to be added within the first 2 days after the initiation of the cultures for the down-regulation of CML (MLC) to occur. The down-regulation of MLC responses could not be shown to be antigen (donor) specific. Physical separation of DBMC from the responder-stimulator cells using the transwell system abrogated modulation of the CML (and MLC) reactions, suggesting the requirement of cell-cell contact for modulatory effect. The inhibitory activity by DBMC could not be overcome by addition of up to 200 U/ml of exogenous recombinant interleukin 2 to the cultures. However, it could be abrogated by restimulation with donor spleen cells, indicating that donor reactive cells were not deleted by DBMC in short-term cultures. These results showed a regulatory role for DBMC in cellular immune responses against donor cell alloantigens, supporting the rationale for DBMC for facilitating clinical allograft acceptance.

Interferon-gamma-mediated prevention of graft-versus-host disease: development of immune competent and allo-tolerant T cells in chimeric mice.

Recently it was shown that delayed graft-versus-host disease (GVHD) in mice can be completely prevented by repeated injections of interferon-gamma (IFN-gamma). The characteristics of this sustained IFN-gamma-induced chimerism were studied in more detail. First, the potency of IFN-gamma as a modulator of GVHD was tested in a fully H-2 mismatched murine bone marrow transplantation (BMT) model. Donor bone marrow cells (BMC; C57BL/Rij; H-2b) were mixed with increasing numbers of donor spleen cells (SC) and transplanted into lethally irradiated recipients (C3H/Law; H-2k). Secondly, BMC and SC of the IFN-gamma-induced chimeras (C3H/Law; H-2b) were tested on their immunological competence and GVHD inducing capacity. Repeated injections of the host with IFN-gamma were able to prevent GVHD even when up to 10(5) SC were added to the graft; adding higher numbers of SC resulted in a rapid increase in the frequency of lethal GVHD. Donor-derived lymphocytes (H-2b) obtained from chimeric animals were immunocompetent as concluded from Con A stimulation in vitro. Chimeric-derived BMC (H-2b) were mixed with up to 10(7) chimeric SC (H-2b) and transplanted into a new group of lethally irradiated C3H/Law (H-2k) recipients. All transplanted animals survived the latter treatment without any macroscopic signs of histological lesions typical of GVHD. We conclude that IFN-gamma treatment allows the development of mature donor-derived immunocompetent T cells, which are allo-tolerant for the recipient.

The shift of Th1/Th2 ratios induced by portal venous administration of UVB-treated donor spleen cells prolonged mouse cardiac allografts

The shift of Th1/Th2 ratios induced by portal venous administration of UVB-treated donor spleen cells prolonged mouse cardiac allografts

Induction of tolerance to an experimental cardiac allograft through intrathymic inoculation of class II major histocompatibility complex disparate antigens

Indefinite donor-specific tolerance to a cardiac allograft can be induced through pretransplantation intrathymic injection of donor spleen cells and a single intraperitoneal injection of antilymphocyte serum. This study was designed to determine whether this phenomenon was reproducible with grafts differing in either class I major histocompatibility complex only or class II MHC only. Donors of cells and hearts in all experiments were RP rats. Class I MHC disparate grafts were performed by placing an RP heart into a Lewis recipient, and class II disparate grafts were performed with RP donors and Wistar Furth recipients. Lewis ( n = 10) and Wistar Furth ( n = 10) recipients underwent intraperitoneal injection of 1 ml antilympocyte serum and intrathymic injection of 5 × 10 7 RP spleen cells. Three weeks later, heterotopic cardiac transplantation was done with a heart from an RP rat. Control rats had no pretreatment or received antilympocyte serum alone. Without pretreatment, RP hearts survived 7 to 9 days (mean 8 days) in Lewis recipients ( n = 5) and 9 to 14 days (mean 12 days) in Wistar Furth recipients ( n = 5). Antilymphocyte serum alone produced slight prolongation of graft survival. Lewis rats pretreated with class I disparate RP splenocytes and antilympocyte serum had graft survivals of 8 to 27 days (mean 14 days), not significantly different from the results with antilympocyte serum alone. Class II disparate RP grafts placed in pretreated Wistar Furth rats had significant prolongation of graft survival, with four of five grafts surviving longer than 60 days ( p < 0.01 vs antilympocyte serum alone). These results suggest that a disparity at the class II locus of the major histocompatibility complex is critical for the induction of cardiac allograft tolerance after intrathymic inoculation of allogeneic cells. (J T HORAC C ARDIOVASC S URG 1996;112:1315-8)

HLA-DPA1 typing by PCR amplification with sequence-specific primers (PCR-SSP) and distribution of DPA1 alleles in Caucasian, African and Oriental populations.

In the present study PCR primers were designed for detecting all known DPA1 variability, i.e., the presently recognized six DPA1 alleles 0103 to 0401, and also for separation of the four DPA1*02 alleles, by PCR amplification with sequence-specific primers (PCR-SSP). For each sample seven different PCR reactions were performed which allowed the identification of all DPA1 alleles and the resolution of all DPA1 genotypes. Forty-eight cell lines and 100 donor spleen cells were investigated by the DPA1 PCR-SSP technique. In the forty-eight known workshop cell-lines no false positive or false negative results were obtained. The 100 donor spleen cells were only typed by the PCR-SSP technique and in their DNAs only one or two DPA1 alleles were found. Twenty cell lines and twenty donor spleen cells were typed on two separate occasions and interpreted blindly. The reproducibility between the repeated typings was 100%. The length of the specific products ranged from 103 to 258 base pairs and the amplification patterns obtained were easy to interpret. In conclusion, DPA1 typing by the PCR-SSP method is an accurate typing technique with high sensitivity, specificity and reproducibility. Analysis of the distribution of DPA1 alleles was performed in 100 Caucasian samples, 100 African samples and 80 Oriental samples, including separation of the four of HLA-DPA1 alleles. Each ethnic group appeared to have one (Caucasians), or two (Africans and Orientals), frequent DPA1 allele(s) and a high frequency of DPA1 homozygotes, suggesting that, like for the DPB1 locus, balancing selection does not appear to be affecting the evolution of the DPA1 locus.

Prolongation of cardiac allograft survival by intraportal injection of donor antigens—Differential mechanisms according to the timing of injection

Recently, we reported that intraportal (IP) injection of donor spleen cells (SPCs) before transplantation as well as at the time of transplantation significantly prolongs cardiac allograft survival in rats (7). Long-term establishment of chimerism induced by intraportal administration of SPCs could be a part of this prolongation. In this study, we examined the effect of irradiation of SPCs as a source of donor antigens on cardiac allograft survival. Experiments were carried out using DA (RT1 a) as the donor and BUF (RT1 b) as the recipient strain. Fifty million irradiated or nonirradiated SPCs were injected either intravenously (i.v.) or intraportally (i.p.) on day -10 or day 0, the day of cardiac allografting. Untreated animals rejected allografts within a mean survival time (MST) of 7.2 ± 0.8 days ( n = 5). Injection (i.p.) of SPCs on both day -10 ( n = 4) and day 0 ( n = 6) induced significant prolongation of MST over the control (19.0 ± 4.7, 14.2 ± 2.1 days; p < 0.001 vs. control), while i.v. injection of SPCs on either day -10 ( n = 4) or day 0 ( n = 4) failed to do so (9.2 ± 1.0, 8.5 ± 0.6 days). Significant prolongation was still observed when irradiated SPCs were injected on day -10 ( n = 4; MST: 19.0 ± 5.4 days, p < 0.002 vs. control), but not when injected on day 0 ( n = 5; MST: 9.4 ± 2.1 days). These data suggest that the immunosuppressive effect of i.p. injection of donor SPCs could be induced by differential mechanisms according to the timing of inoculation of donor antigens.

Transfer of type II collagen‐induced arthritis from DBA/1 to severe combined immunodeficiency mice can be prevented by blockade of Mac‐1

Collagen-induced arthritis in susceptible mice is widely accepted as an experimental model for human rheumatoid arthritis (RA). We have investigated the role of the Mac-1 integrin beta 2 in the development and maintenance of arthritis by means of in vivo administration of 5C6 monoclonal antibody (mAb) to block this receptor. Injection of a single dose of 5C6 mAb (0.5 mg, intraperitoneally) prior to the expected onset of collagen-induced arthritis in DBA/1 mice diminished the severity of subsequent disease in these animals, as assessed both clinically and histologically (P < 0.01, chi 2). In the DBA/1 to severe combined immunodeficiency (SCID) transfer model of arthritis, the incidence of clinical arthritis was significantly reduced in SCID mice receiving maintained 5C6 treatment commencing the day prior to administration of donor splenocytes. Histological evaluation of joints from animals without clinically evident arthritis confirmed the absence of an inflammatory infiltrate in 22/27 joints examined. In a minority of these joints, however, synovial hyperplasia was apparent. In contrast, delaying antibody administration until 10 days after donor spleen cell transfer failed to protect three of five SCID recipients. These results confirm a functional role for Mac-1 in the generation of collagen-induced arthritis in mice. Since mAb 5C6 is non-cytotoxic, its action must be by blockade of the interactions between Mac-1 and its natural ligand(s). Our findings support the hypothesis that cells expressing Mac-1 play an important role in the induction and maintenance of joint damage in collagen-induced arthritis.

Late adjunctive therapy with single doses of rapamycin in skin-allografted mice treated with antilymphocyte serum and donor bone marrow cells

Temporary donor-specific unresponsiveness induced by treatment of skin allografted mice with antilymphocyte serum (ALS) and donor bone marrow cells (BMC) can be converted to long-term graft survival and tolerance by adding adjunctive immunosuppressive agents, including rapamycin (Rapa). Rapa was given in a suboptimal dosing schedule to probe several aspects of its use in the promotion of tolerization. Single doses were given at 2 weeks post-transplantation to recipients prepared with ALS and donor BMC. Graft survival was markedly prolonged in a dose-dependent fashion by day +14, Rapa, doses ranging from 0.75 to 6.0 mg/kg. Indefinite (> 300 day) graft survival was observed in 26% of recipeints given the highest Rapa done. Short-term treatment with cyclosporin A (CsA) or deoxyspergualin (DSG) was ineffective when injected at this time. Rapa augmented the tolerizing effect of grafting with skin from newborn mice but had no significant additive or synergistic effects with the short course of CsA or with DSG given on days +1 to +3, even though the latter prolonged graft survival when added to the ALS/BMC protocol. Single doses of Rapa on day +1 also prolonged graft survival, but without any of the grafts surviving indefinitely. Later dosing on day +28 resulted in > 70% of grafts surviving > 300 days. Challenge grafting of these mice after day +300 resulted in delayed rejection of donor strain, but not third-party skin grafts. Rapa was very effective when given as widely spaced doses on days +14 and +49. Also, grafts showing the earliest signs of rejection could be rescued with a single Rapa dose in recipients treated with ALS and BMC but not ALS alone. Transfer of prolonged graft survival with spleen cells from ALS plus BMC treated recipients was not adversely affected by Rapa given to the suppressor-like spleen cell donors approximately 1 week before cell harvest. We conclude that the use of Rapa as an adjunctive agent in allograft recipients treated with ALS plus donor BMC is very flexible in terms of timing of administration, and that the drug can be effectively given as widely spaced doses or as a rescue agent after ALS/BMC treatment. Additionally, an active immunoregulatory mechanism induced by ALS/BMC treatment appears to be spared by Rapa.

Induction of immunological tolerance to islet allografts

T-cell dependent activation of resting B cells involves the interaction of gp39 on T cells with its receptor, CD40, on B cells. We administered either a combination of T-cell-depleted splenic lymphocytes and anti-gp39 monoclonal antibody or antibody alone to establish islet allografts in mice without continuous immunosuppression. Fully allogeneic H-2q FVB islets were permanently accepted by chemically diabetic H-2b C57BL/6 mice provided that the recipients were pretreated with both T-cell-depleted donor spleen cells and anti-gp39 antibody. Antibody alone was less effective in prolonging allograft survival, but we did observe that anti-gp39 mAb alone can exert an independent, primary effect on islet allograft survival that was dose dependent. Targeting gp39, in combination with lymphocyte transfusion, might prove suitable for tolerance induction and allotransplantation without immunosuppression.