Evidence that HLA class II disparity is required for the induction of renal allograft enhancement by donor-specific blood transfusions in man

Reciprocal HLA-DR allogenicity between mother and child affects pregnancy outcome parameters

Successful pregnancy outcome depends on local immunoregulatory mechanisms preventing a detrimental immune response towards the semi-allogeneic fetus. We investigated the influence of HLA-DR (in)compatibility on pregnancy outcome parameters in 480 women. The parameters tested were birth weight, individualized birthweight ratio (IBR), gestational age, and maternal highest diastolic blood pressure. Irrespective of pregnancy complications, maternal-fetal HLA-DR incompatibility resulted in increased IBR. We conclude that reciprocal HLA-DR allogenicity between mother and child positively affect pregnancy outcome parameters.

HLA associations and HLA sharing in recurrent miscarriage: A systematic review and meta-analysis

PROBLEM

The aim of this meta-analysis was to evaluate whether specific maternal HLA alleles and HLA sharing of couples are associated with the occurrence of recurrent miscarriage (RM).

METHOD OF STUDY

A systematic literature search was performed for studies that evaluated the association between HLA alleles, HLA sharing and RM. RM was defined as three or more consecutive unexplained miscarriages and a control group was included of women with at least one live birth and no miscarriages in their history. Meta-analyses were performed and the pooled odds ratio (OR) was calculated.

RESULTS

We included 41 studies. Selection bias was present in 40 studies and information bias in all studies. Meta-analyses showed an increased risk of RM in mothers carrying a HLA-DRB1*4 (OR 1.41, 95% CI 1.05-1.90), HLA-DRB1*15 (OR 1.57, 95% CI 1.15-2.14), or a HLA-E*01:01 allele (OR 1.47, 95% CI 0.20-1.81), and a decreased risk with HLA-DRB1*13 (OR 0.63, 95% CI 0.45-0.89) or HLA-DRB1*14 (OR 0.54, 95% CI 0.31-0.94). Pooling results for HLA sharing showed that HLA-B sharing (OR 1.39, 95% CI 1.11-1.75) and HLA-DR sharing (OR 1.57, 95% CI 1.10-1.25) were both associated with the occurrence of RM.

CONCLUSION

Although the present systematic review and meta-analysis demonstrates that specific HLA alleles and HLA sharing are associated with RM, a high degree of bias was present and therefore observed results should be interpreted carefully.

The influence of inherited and noninherited parental antigens on outcome after transplantation

Contact between the immune systems of mother and child during pregnancy has an impact on transplantation later in life. Exposure to inherited paternal human leukocyte antigens (HLA) (IPA) and the noninherited maternal HLA antigens (NIMA) can lead to either immunization or tolerization. Exposure to IPA seems to have a more immunizing effect as the mature immune system of a mother can form anti-HLA antibodies against the foreign paternal HLA molecules. On the other hand, exposure of a child to the NIMA antigens during pregnancy may lead to NIMA-specific tolerance. This review provides an overview of the current knowledge on the impact of this fetal-maternal interaction on the alloimmune response and clinical transplantation.

The effect of noninherited maternal antigens in allogeneic transplantation

Confrontation of the unborn child immune system with the noninherited maternal antigens (NIMAs) has a lifelong modulating impact on the immune response of the child against the NIMAs. In this review we summarize the clinical evidence for the existence of the NIMA effect, discuss the possible cellular and molecular basis of the phenomenon, and outline the necessity of further clinical research.

The importance of H2 haplotype sharing in the induction of specific unresponsiveness by pretransplant blood transfusions

BACKGROUND

The beneficial effect on graft survival achieved by pretransplant blood transfusions is well established. Previous studies have shown that the degree of major histocompatibility complex (MHC) (mis)-match between the transfusion donor and the recipient plays a determining role. However, other factors are also involved. In this study, we explored the hypothesis that, in addition to sharing of MHC antigens between the transfusion donor and the recipient, the MHC type of the organ donor is also of importance.

METHODS

To mimic the human situation, F1 mice, rather than inbred strains, were pretreated with haplotype-shared allogeneic whole blood transfusions and transplanted with hearts of organ donors with different matched or mismatched H2 haplotypes.

RESULTS

When a heart was transplanted 1 week after donor-specific transfusion (DST; blood transfusion donor=organ donor), an excellent prolongation of graft survival was obtained (median survival time: 77 days vs. 9 days in untreated mice). However, this was only the case when a haplotype was shared with the recipient; a DST given with no match between organ donor (=BT donor) and recipient did not induce any prolongation. Furthermore, in order to obtain the optimal beneficial effect of a haplotype-shared blood transfusion, the other haplotype of the transfusion donor had to be mismatched with the recipient. The immunogenetic studies showed that haplotype-shared blood transfusions in combinations where the H2 type of the organ donor differed from that of the transfusion donor are less efficient in inducing prolongation of graft survival.

CONCLUSIONS

These results demonstrate that haplotype-shared blood transfusions can induce a significantly prolonged survival of cardiac allografts in F1 mice. The immunogenetic studies suggest that presentation of alloantigen-derived peptides in the context of self MHC (the indirect pathway of allorecognition) is essential for the beneficial effect of haplotype-shared blood transfusions.

Survival of Donor Leukocyte Subpopulations in Immunocompetent Transfusion Recipients: Frequent Long-Term Microchimerism in Severe Trauma Patients

We recently reported detection of a transient increase in circulating donor leukocytes (WBCs) in immunocompetent recipients 3 to 5 days posttransfusion (tx) (Blood 85:1207, 1995). We have now characterized survival kinetics of specific donor WBC subsets in additional tx populations. Eight female elective surgery patients (pts) were sampled pre-tx and on days 1, 3, 5, 7, and 14 post-tx. Ten female trauma pts transfused with a total of 4 to 18 U of relatively fresh red blood cells were sampled up to 1.5 years post-tx. WBC subsets from frozen whole blood were isolated using CD4, CD8 (T cell), CD15 (myeloid), and CD19 (B cell) antibody-coated magnetic beads. Donor WBCs were counted by quantitative polymerase chain reaction (PCR) of male-specific sex determining region (SRY) sequences. PCR HLA typing and mixed leukocyte reaction (MLR) between recipient and donor WBCs were performed on two of the trauma tx recipients who had long-term chimerism of donor cells post-tx. In 6 of 8 female surgery pts, circulating CD4+ male donor cells peaked at day 3 or 5 (0.01 to 1 cell/μL), followed by clearance by day 14. In 7 of 10 female trauma pts, we observed multilineage persistence of male donor WBCs (CD4, CD8, CD15, CD19) for 6 months to 1.5 years post-tx at concentrations of 10 to 100 cells/μL. In 2 trauma recipients studied, MLR showed no, or very low, response to WBC of the single donor implicated as the source of microchimerism by HLA typing. Establishment of long-term multilineage chimerism in trauma recipients is probably caused by engraftment of donor stem cells and mutual tolerance between recipient and donor leukocytes. A better understanding of factors determining clearance versus chimerism of transfused leukocytes is critical to prevention of alloimmunization and transfusion-induced graft-versus-host disease, and, potentially, to induction of tolerance for transplantation.

Survival of Donor Leukocyte Subpopulations in Immunocompetent Transfusion Recipients: Frequent Long-Term Microchimerism in Severe Trauma Patients

We recently reported detection of a transient increase in circulating donor leukocytes (WBCs) in immunocompetent recipients 3 to 5 days posttransfusion (tx) (Blood 85:1207, 1995). We have now characterized survival kinetics of specific donor WBC subsets in additional tx populations. Eight female elective surgery patients (pts) were sampled pre-tx and on days 1, 3, 5, 7, and 14 post-tx. Ten female trauma pts transfused with a total of 4 to 18 U of relatively fresh red blood cells were sampled up to 1.5 years post-tx. WBC subsets from frozen whole blood were isolated using CD4, CD8 (T cell), CD15 (myeloid), and CD19 (B cell) antibody-coated magnetic beads. Donor WBCs were counted by quantitative polymerase chain reaction (PCR) of male-specific sex determining region (SRY) sequences. PCR HLA typing and mixed leukocyte reaction (MLR) between recipient and donor WBCs were performed on two of the trauma tx recipients who had long-term chimerism of donor cells post-tx. In 6 of 8 female surgery pts, circulating CD4+ male donor cells peaked at day 3 or 5 (0.01 to 1 cell/μL), followed by clearance by day 14. In 7 of 10 female trauma pts, we observed multilineage persistence of male donor WBCs (CD4, CD8, CD15, CD19) for 6 months to 1.5 years post-tx at concentrations of 10 to 100 cells/μL. In 2 trauma recipients studied, MLR showed no, or very low, response to WBC of the single donor implicated as the source of microchimerism by HLA typing. Establishment of long-term multilineage chimerism in trauma recipients is probably caused by engraftment of donor stem cells and mutual tolerance between recipient and donor leukocytes. A better understanding of factors determining clearance versus chimerism of transfused leukocytes is critical to prevention of alloimmunization and transfusion-induced graft-versus-host disease, and, potentially, to induction of tolerance for transplantation.

Impact of transfusions and acute rejection on posttransplantation donor antigen-specific responses in two study populations. Cooperative Clinical Trial in Transplantation Research Group

BACKGROUND

We participated in a protocol supported by the National Institutes of Allergy and Infectious Disease, Cooperative Clinical Trial in Transplantation (CCTT), which was designed to investigate the effect of peritransplant donor-specific transfusion in non-HLA-identical living donor kidney recipients.

METHODS

We determined the donor antigen-specific responses at 1 year after transplantation for the 79 CCTT donor-recipient combinations in this study. A lower rate of donor antigen-specific hyporeactivity was seen in the CCTT recipients (6 of 79=8%) versus our recipients at the University of Minnesota who underwent transplantation in the same period (9 of 55=16%, P=0.16) and versus our combined historical data (33 of 131=25%, P=0.002). Therefore, we studied the differences in the two recipient populations to determine why hyporeactivity was lower in the CCTT group than at our center.

RESULTS

Significant differences were seen in the acute rejection rates and the frequency of pretransplantation random transfusion. Overall and early (<3 month) acute rejection rates were higher in CCTT versus Minnesota recipients (overall: 51% vs. 20%, P=0.001) (early: 43% vs. 16%, P=0.001). The frequency of pretransplantation random transfusion was 40% for CCTT recipients (34%) versus 80% for Minnesota recipients (75%) (P=0.0004).

CONCLUSIONS

These results provide provocative, although not conclusive, evidence for the importance of pretransplantation transfusion and acute rejection episodes in the development of donor antigen-specific hyporeactivity. Pre-, peri-, and posttransplantation clinical events undoubtedly have an impact on posttransplantation immune parameters.

Stored blood--an effective immunosuppressive method for transplantation of kidneys from unrelated donors. An 11-year follow-up

Thirty-seven patients were submitted to kidney transplantation after transfusion at 2-week intervals with 4-week stored blood from their potential donors. All patients and donors were typed for HLA-A-B and DR antigens. The patients were also tested for cytotoxic antibodies against donor antigens before each transfusion. The percentage of panel reactive antibodies (PRA) was determined against a selected panel of 30 cell donors before and after the transfusions. The patients were immunosuppressed with azathioprine and prednisone. Rejection crises were treated with methylprednisolone. The control group consisted of 23 patients who received grafts from an unrelated donor but who did not receive donor-specific pretransplant blood transfusion. The incidence and reversibility of rejection episodes, allograft loss caused by rejection, and patient and graft survival rates were determined for both groups. Non-parametric methods (chi-square and Fisher tests) were used for statistical analysis, with the level of significance set at P < 0.05. The incidence and reversibility of rejection crises during the first 60 post-transplant days did not differ significantly between groups. The actuarial graft and patient survival rates at five years were 56% and 77%, respectively, for the treated group and 39.8% and 57.5% for the control group. Graft loss due to rejection was significantly higher in the untreated group (P = 0.0026) which also required more intense immunosuppression (P = 0.0001). We conclude that transfusions using stored blood have the immunosuppressive effect of fresh blood transfusions without the risk of provoking a widespread formation of antibodies. In addition, this method permits a reduction of the immunosuppressive drugs during the process without impairing the adequate functioning of the renal graft.

Donor-specific transfusion and donor bone marrow infusion in renal transplantation tolerance: a review of efficacy and mechanisms

The ultimate goal in transplantation is modulation of the immune response to produce tolerance without immunosuppression. To date only a state of pseudotolerance for the allograft has been achieved through the use of potent pharmacologic and biologic manipulations. Despite these manipulations to prevent acute rejection, chronic rejection eventually results in graft failure. Thus, different strategies have been sought to induce tolerance and prevent acute and chronic rejection. Historically, donor-specific transfusion (DST) was one such strategy attempted. Donor-specific transfusion has been used primarily in living donor organ transplantation. With the concern that DST may sensitize patients, thereby preventing transplantation and introduction of cyclosporine, the use of DST was curtailed. More recently, donor bone marrow (DBM) infusion at the time of cadaveric transplantation has been used to facilitate development of microchimerism and tolerance to abrogate acute and chronic rejection. However, DBM infusion may predispose the recipient to graft-versus-host disease and is not easily accomplished in living donor organ transplantation. The potentially immunomodulating and tolerizing mechanisms of DST and DBM infusion are similar and include induction of anergy, stimulation of anti-anti-HLA antibodies, provision of soluble HLA antigen, suppressor cell and/or veto cell activity, clonal deletion, regulation of cell surface molecules, regulation of cytokines, promotion of microchimerism, or a combination of these. Of these mechanisms, microchimerism with the concomitant persistence of soluble donor HLA antigen is felt by many to be the most important. Although microchimerism is detectable in many patients who are tolerant of their grafts, there is no clear evidence that chimerism is responsible for the induction or maintenance of tolerance.

Prevention of donor-specific T-cell unresponsiveness after buffy-coat-depleted blood transfusion

The immunosuppressive effect of blood transfusions has been demonstrated in several clinical studies. The effect is probably mediated by HLA-class-II-bearing donor leucocytes, because results from laboratory tests show specific down-regulation of the recipient's T-Cell response after administration of blood from donors sharing one HLA haplotype with the recipient. In the present study we evaluated the immunosuppressive potential of buffy-coat-depleted red cell transfusions in patients waiting for renal transplantation, by measuring the frequency of cytotoxic precursor T cells before and after transfusion. The buffy coat was removed from whole blood by the Optipress system and resulted in > 97% depletion of lymphocytes and monocytes. A single transfusion of HLA-haplotype-matched buffy-coat-depleted red cells induced donor-specific down-regulation of T-cell responses in only two of 14 patients. Since HLA-class-II-bearing cells are also involved in the induction of anti-HLA antibodies, we evaluated retrospectively the incident of HLA alloimmunization after a single transfusion of buffy-coat-depleted red cells. No anti-HLA antibodies were found in 140 patients at risk for primary immunization. We conclude that the poor immunological responses found after a single transfusion of HLA-haplotype-matched buffy-coat-depleted red cells is due to the small number of residual HLA-class-II-bearing donor cells. This blood component should not be used for induction of immunosuppression.

Pretransplantation blood transfusion revisited

BACKGROUND

Blood transfusion before organ transplantation has a beneficial effect on allograft survival; the mechanism of this effect has remained a mystery. In murine models, the presence of common histocompatibility antigens in the blood donor and the recipient favors the induction of allograft tolerance.

METHODS

To investigate the effect of HLA compatibility between blood donor and recipient on the induction of allograft tolerance, we determined the relative frequency of cytotoxic T-lymphocyte precursors specific for donor cells before and at several times after blood transfusion in 23 patients awaiting a first renal transplant. We correlated the results with the presence of shared HLA antigens.

RESULTS

T-cell nonresponsiveness against donor cells developed after blood transfusion in 10 of the 23 patients. Tolerance developed only if the blood donor and the recipient had one HLA haplotype or at least one HLA-B and one HLA-DR antigen in common (as was observed in 9 of these 10 patients). Tolerance developed relatively late after blood transfusion (one to two months) and was long-lasting. No decline in the T-cell response against donor alloantigens was observed in any of the 13 patients who received transfusions without having HLA-antigen compatibility with the donor.

CONCLUSIONS

Blood transfusion in which there is a common HLA haplotype or shared HLA-B and HLA-DR antigens induces tolerance to donor antigens. This finding may lead to the development of new strategies with which to induce tolerance for transplantation after blood transfusion. Perhaps transplant donors will be selected not only by HLA-antigen matching, but also on the basis of acceptable HLA-antigen mismatches associated with T-cell non-responsiveness induced by selected blood transfusion.

The influence of allogeneic cells on the human T and B cell repertoire

Clinical transplantation is often complicated by rejection episodes, in which the immune system of the recipient reacts to the foreign transplantation (HLA) antigens on the graft. This immune response includes humoral and cellular components. In the first, B lymphocytes form antibodies to the HLA alloantigens. In the second, CD8+ T lymphocytes recognize and react to HLA class I antigens, and CD4+ T cells react to HLA class II antigens. The frequency and severity of these rejection episodes can be diminished by immunosuppressive drugs, HLA matching between donor and recipient, and immune modulation by blood transfusion. Effective HLA matching between donor and recipient is not always possible and often not necessary. Insight into the factors that influence the T and B cell repertoire after blood transfusion might lead to new approaches to improve graft survival.