Long-term survival of heart and kidney allografts is threatened by the development of chronic rejection. Analysis of the relationship between reversible acute rejection episodes and actuarial survival at 5 years showed an inverse correlation suggesting that early cellular events may trigger antibody-mediated chronic rejection. In both heart and kidney allograft recipients producing anti-HLA antibodies we found a significant decrease in the 5-year graft survival rate. However, there was heterogeneity among anti-HLA antibody producers with respect to the development of anti-idiotypic antibodies. The actuarial 5-year graft survival was significantly higher in patients with Ab2 compared to patients without.