IMMUNOGLOBULIN-M ANTIBODIES IN TRANSPLANTED HUMAN HEARTS

We have studied 56 human hearts before and after transplantation for t he presence of immunoglobulin M. None of the 56 time-zero biopsy speci mens studied contained immunocytochemically detectable immunoglobulin M, but they all had immunoglobulin M deposits on vascular endothelial cells after transplantation. The vascular location of immunoglobulin M was confirmed in double-antibody experiments with antibodies to von W illebrand factor and immunoglobulin M. None of the immunoglobulin M an tibody reactivity was shown to colocalize with complement. Biopsy spec imens from 29 of the 56 patients contained abundant deposits of immuno globulin M. These patients were clinically stable, and only one of the m has died. Biopsy specimens from 27 of the 56 patients had scant depo sits of immunoglobulin M. These patients were clinically unstable; eig ht of them have died, and one has undergone retransplantation. In addi tion, biopsy specimens from stable allografts contained fewer fibrin d eposits than biopsy specimens from unstable grafts, suggesting a prote ctive role for non-complement fixing immunoglobulin M. The observation that immunoglobulin deposits were found soon after transplantation pr ompts us to consider them to be natural antibodies. Efforts to identif y the antigen for immunoglobulin M natural antibodies in heart transpl ant recipients are currently under study.