Correlation of donor antigen-specific hyporeactivity with allogeneic microchimerism in kidney and lung recipients

Microchimerism and renal transplantation: doubt still persists

OBJECTIVE

We sought to study microchimerism in a group of kidney transplant recipients.

MATERIALS AND METHODS

In this study, the peripheral blood microchimerism (PBM) after renal transplantation was retrospectively evaluated in 32 male-to-female recipients of living unrelated or cadaveric donor renal transplants. Using a nested polymerase chain reaction (PCR) amplification specific for SRY region of the Y chromosome, microchimerism was detected with a sensitivity of 1:1,000,000. Recipients were compared according to the presence of PBM, acute and chronic rejection episodes, type of allotransplant, recipient and donor age at transplantation, previous male labor or blood transfusion, allograft function (serum creatinine level), and body mass index.

RESULTS

Among 32 recipients, 7 (21.9%) were positive for PBM upon multiple testing at various posttransplant times. All microchimeric recipients had received kidneys from living unrelated donors. No significant difference was observed with regard to other parameters. In addition the acute rejection rate in the microchimeric group was 3 (42%) versus 4 (16%) in the nonmicrochimeric recipients (not significant).

CONCLUSION

Our results suggested better establishment of microchimerism after living donor kidney transplantation. However, doubt persists concerning the true effect of microchimerism after renal transplantation. It seems that microchimerism alone has no major protective role upon renal allograft survival.

Improved long-term graft function in kidney transplant recipients with donor antigen-specific hyporeactivity

We investigated the development of donor antigen-specific hyporeactivity by using donor cells as stimulator cells in the MLC and comparing the pre- and post-transplant responses of peripheral blood mononuclear cells. Twenty-two haploidentical pediatric living-relative donor recipients treated with daclizumab, methylprednisone, mofetil mycophenolate and calcineurin inhibitors were tested for study. Of these, 50% of the recipients developed in vitro donor antigen-specific hyporeactivity. The recipients who did so have higher creatinine clearance levels at 12, 24 and 36 months post-transplant (104, 92 and 81 mL/min/1.73 m(2), respectively) than those who remained responsive to donor antigens (77, 74 and 70 mL/min/1.73 m(2)) (p < 0.05). Acute rejection episodes were not observed; however, no recipients with donor-specific hyporeactivity have been diagnosed with CAN, unlike three recipients who remained responsive to donor antigens (0% vs. 27.3%, p = 0.06). Differences in accumulative doses of methylprednisone and mofetil mycophenolate were observed between hyporeactivity- and response-patients to donor antigens at the three years end-point (1.9 +/- 0.8 g/m(2) vs. 4.2 +/- 0.5 g/m(2), and 277 +/- 89 g/m(2) vs. 672 +/- 16.0 g/m(2); p < 0.01 and <0.02, respectively). We conclude that the development of donor antigen-specific hyporeactivity correlate with improved graft function and may permit lower immunosuppression.

Microchimerism and rejection: a meta-analysis

AIMS

To study the relationship between graft rejection and microchimerism with and without donor bone marrow infusion in recipients of kidney, liver, heart and lung transplants. Selection of manuscripts. Thirty-seven manuscripts presenting clinical data on microchimerism and rejection, published between 1991 and 1997, were identified. Of these, 16 were excluded due to duplication or insufficient data. Inclusion criteria were data on microchimerism, bone marrow infusion and rejection episodes.

STATISTICAL TESTS

A mixed effect logistic model was used to test for homogeneity of transplant centers. The centers were found to be homogeneous for rejection rates controlling for microchimerism and bone marrow infusion. Using rejection episodes at 3, 6, and 12 months post-transplant as the outcome, we evaluated logistic regression models to derive odds ratios for rejection with microchimerism and with bone marrow infusion for each organ.

RESULTS

Microchimerism was generally associated with a higher incidence of acute rejection for heart, lung, and kidney transplants and a lower incidence for liver transplants, especially at 12 months and above. Bone marrow infusion decreased the risk of acute rejection for heart transplants and increased the risk for lung and, to a lesser extent, for liver transplants. No consistent effect was seen in kidney transplants. At 12 months and longer, microchimerism was associated with a decreased incidence of chronic rejection in recipients of lung transplants, but there were insufficient data to determine this outcome for other organs.

CONCLUSIONS

(i) Microchimerism was detected in the majority of patients. (ii) The effect of microchimerism and bone marrow infusion on rejection episodes varied with the organ and, for a given organ, it was time-dependent. (iii) These findings demonstrate the need for more extensive studies on microchimerism and donor-specific hyporesponsiveness.

Microchimerism and blocking activity in women with recurrent spontaneous abortion (RSA) after alloimmunization with the partner's lymphocytes

Alloimmunization therapy using the partner's leukocytes has been reported to be effective in preventing the failure of pregnancy in patients who have suffered RSA of unknown cause. After alloimmunization, several investigators have reported the presence of blocking factors (BF) in women with successful pregnancies in in vitro assays of lymphocyte response. The recent discovery of small numbers of ubiquitous donor cells (microchimerism) in human transplants up to 29 years post-transplantation has raised questions about the migration of the chimeric cells and their role in the induction and perpetuation of tolerance. We have investigated the production of BF in the mixed lymphocyte reaction (MLR) before and in some patients after alloimmunization and its possible relation with the development of microchimerism (M). Before the treatment we studied 14 couples with three or more abortions who were evaluated clinically to rule-out genetic, structural, endocrine, infectious and autoimmune causes. The M study was done by nested PCR-SSP technique with HLA-DR alleles, before and after 30 days of the last immunization. Before the treatment only one patient was M positive and none were BF positive with inhibition effect (IE) > 50. Only eight underwent treatment. The patients had between three and nine alloimmunizations (x = 4.7). After treatment, all patients were M positive with IE > 50. Six months after the last immunization, four patients are M positive with IE > 50. In conclusion, the hypothesis proposes that alloimmunization establishes a state of microchimerism that would be the necessary allogeneic stimulus for T-cell activation, and the induction or maintenance of tolerance to the fetus during pregnancy. reserved.

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.

Analysis of the relationship between chimerism and the allgeneic humoral response

BACKGROUND

Persistence of antigens has been suggested to play a role in two opposing immunological phenomena: tolerance and memory. Therefore, we studied the impact of chimerism on alloreactive antibody (allo-Ab) production in kidney transplant patients.

METHODS

Thirty-five female renal transplant recipients of male donor organs were classified into the following groups: group 1, 13 sensitized uremic patients on dialysis; group 2, 5 nonsensitized uremic patients on dialysis; group 3, six sensitized patients experiencing graft rejection (3 acute vascular, 1 acute cellular, and 2 chronic); and group 4, 11 nonsensitized with functioning allografts (9 with good function, 1 with acute cellular rejection, and 1 with chronic rejection). Mean duration of dialysis after graft failure was similar in groups 1 (56+/-29.7 months) and 2 (41.8+/-42.4 months), as was dialysis efficiency. Chimerism was measured indirectly in the peripheral blood lymphocytes by polymerase chain reaction amplification of a specific Y chromosome DNA gene sequence with a detection sensitivity limit of 1 male cell per 1 million female cells. Allo-Ab production was measured by the PRA-STAT enzyme-linked immunosorbent assay (Sangstat) method.

RESULTS

Chimerism was observed in 60% of groups 1 and 2, 83% of group 3, and 82% of group 4. Among all groups, graft existence, irrespective of its function, positively predicted chimerism in 92% with a sensitivity of 88% and a specificity of 78%. In group 3, all three patients with acute vascular rejection had chimerism and donor-specific allo-Abs. In group 4, eight of the nine patients with no rejection had chimerism.

CONCLUSION

Chimerism relates to persistence of allogeneic stimulus irrespective of its function. Chimerism did not confer protection against allo-Ab production or vascular rejection, and its existence was not crucial for sustenance of allo-Ab production.