H-Y antibody development associates with acute rejection in female patients with male kidney transplants

Abstract

Background: Human minor histocompatibility antigens (mHA) and clinically relevant immune responses to them have not been well defined in organ transplantation. We hypothesized that women with male kidney transplants would develop antibodies against H-Y, the mHA encoded on the Y-chromosome, in association with graft rejection.

Methods: We tested sera from 118 consecutive transplant recipients with kidney biopsies. Antibodies that specifically recognized the recombinant H-Y antigens RPS4Y1 or DDX3Y were detected by IgG enzyme-linked immunosorbent assay and western blotting. Immunogenic epitopes were further identified using overlapping H-Y antigen peptides for both the H-Y proteins.

Results: In the 26 female recipients of male kidneys, H-Y antibody development posttransplant (1) was more frequent (46%) than in other gender combinations (P<0.001), (2) showed strong correlation with acute rejection (P=0.00048), (3) correlated with plasma cell infiltrates in biopsied kidneys (P=0.04), and (4) did not correlate with C4d deposition or donor-specific anti-human leukocyte antigen (HLA) antibodies. Of the two H-Y antigens, RPS4Y1 was more frequently recognized (P=0.005).

Conclusion: This first demonstration of a strong association between H-Y antibody development and acute rejection in kidney transplant recipients shows that in solid organ allografts, humoral immune responses against well defined mHA have clear clinical correlates, can be easily monitored, and warrant study for possible effects on long-term graft function.

FIGURE 1

H-Y antibodies are more frequently detected in M→F patients. Frequency of patients with RPS4Y1 and/or DDX3Y Ab at the time of biopsy. Heights of the stacked bars represent the frequency in each transplant group of H-Y antibodies detected by IgG ELISA at the time of biopsy. De novo antibodies against DDX3Y or RPS4Y1 at the time of biopsy are shown by the hatched areas. Both total (P<0.01) and de novo (P<0.001) H-Y antibody in M→F vs. each other group were highly significant (Fisher’s exact test, #P<0.001). Other group comparisons did not show statistical significance.

FIGURE 2

Frequency of antibody responses against RPS4Y1 and DDX3Y peptides in 26 M→F patients. Sera from 26 M→F patients were tested by IgG ELISA, for antibodies against 23 overlapping RPS4Y1 peptides and 93 overlapping DDX3Y peptides. The solid bars indicate the frequency of the antibody responses to each peptide and the open bars report the number of amino acids disparate for X vs. Y homologs by comparing RPS4YX/DDX3X sequence with each RPS4Y1/DDX3Y peptide tested.

FIGURE 3

De novo H-Y antibodies associate with AR in M→F patients. Sera from 26 M→F patients with allograft dysfunction and who underwent biopsy were tested for de novo anti-H-Y by IgG ELISA. Fourteen patients had biopsy confirmed AR and 12 did not (non-AR). Sera from 15 patients with stable graft function were also tested as a control group. De novo antibody detection was significantly greater in patients with AR compared with patients with non-AR or stable graft function (Fisher’s exact test, # P<0.001).