Non-HLA transplantation immunity revealed by lymphocytotoxic antibodies.

Background: The presence of panel-reactive antibodies (PRA) against HLA antigens before transplantation is associated with early rejection of kidney grafts from cadaver donors. Transplants from HLA-identical sibling donors do not provide a target for antibodies to HLA antigens and should therefore not be affected by PRA.

Methods: Data from the Collaborative Transplant Study were used to examine the influence of PRA on graft survival. Uncensored graft survival and death-censored graft survival were calculated, and the data were analysed by multivariate Cox's regression methods.

Findings: Among recipients of HLA-identical sibling transplants, 3001 patients with no PRA had significantly higher 10-year graft survival (72.4% [SE 1.1]) than 803 patients with 1-50% PRA (63.3% [2.5]; p=0.0006) or 244 patients with more than 50% PRA (55.5% [4.0]; p<0.0001). The effect of PRA became apparent after the first post-transplant year and was, therefore, strikingly different from the early steep decline in graft survival during the first year associated with PRA in recipients of cadaver kidneys. We could not discern whether graft loss was a direct effect of non-HLA humoral sensitisation or whether PRA served as an indicator of heightened immunity against non-HLA transplantation antigens.

Interpretation: PRA reactivity is strongly associated with long-term graft loss in kidney transplants from HLA-identical sibling donors.

Relevance To Practice: Our findings suggest that non-HLA immunity has a much stronger role in clinical transplantation than previously thought. In contrast to immunity against HLA mediated by antibodies present before transplantation, which leads to early acute graft rejection, non-HLA immunity is associated with chronic graft loss. The possibility of identifying recipients at increased risk of late graft loss before transplantation could be used to devise specific immunosuppressive strategies for these patients.