Clinical impact of H-Y alloimmunity.

H-Y antigens are a group of minor histocompatibility antigens encoded on the Y-chromosome with homologous H-X antigens on the X-chromosome. The disparate regions of the H-Y antigens are highly immunogenic and play an important role in understanding human alloimmunity. In this review, we investigate the history of H-Y antigen discovery along with their critical contributions in transplantation and pregnancy. In hematopoietic cell transplantation, male recipients with female donors who become seropositive for B-cell responses as H-Y antibodies following transplantation have increased rates of chronic graft-versus-host disease and decreased rates of relapse. Conversely, female patients who receive male kidney allografts are more likely than other gender combinations to develop H-Y antibodies and reject their allografts. Finally, in the setting of pregnancy, mothers who initially gave birth to boys are more likely to have subsequent pregnancy complications, including miscarriages, in association with H-Y antibody development. H-Y antigens continue to serve as a model for alloimmunity in new clinical scenarios. Our development of more sensitive antibody detection and next-generation DNA sequencing promises to further advance our understanding and better predict the clinical consequences of alloimmunity.