Renal transplantation in the inbred rat. 3. A study of heterologous anti-thymocyte sera.

Heterologous rabbit anti-rat thymocyte sera, its immunoglobulin G fraction, and the bivalent and univalent antibody fragments obtained by pepsin digestion are potent immunosuppressive reagents when tested in a system of renal allotransplantation between the LBN F(1) hybrid and Lewis rat strains. The AT F(ab')(2) is not lymphocytotoxic in vitro but has agglutinating ability, while the AT Fab' neither agglutinates nor is cytotoxic to rat lymphocytes, but will inhibit the in vitro reaction. The AT IgG and the F(ab')(2) are more immunogenic in their host than normal rabbit IgG and F(ab')(2), probably due to increased delivery of the antibody to the immune system.