Alloantibodies Induced by Weaker Histocompatibility Antigens in Rats

Allografts of skin, kidney or lymphoid tissue between H-1 (Ag-B) compatible Fischer and Lewis rats induced alloantibodies that could be detected with a modified 51Cr cytotoxicity assay. Isogeneic or allogeneic complement was efficient in this assay and allowed for greater sensitivity of the cytotoxicity test by decreasing the nonspecific background release of 51Cr from labeled target cells. The alloantibody detected in this test is presumed to be specific for weaker histocompatibility antigens determined by non-H-1 (Ag-B) alleles. Lewis recipients of long-surviving Fischer kidney allografts had relatively high levels of alloantibody present in their serum as early as 8 days after transplantation; these antibody levels gradually decreased during the 7-month observation period reported here. Especially noteworthy is the production and regular detection of serum alloantibodies induced across a weak histocompatibility barrier reflected in kidney allograft survival times normally exceeding 200 days.