Hyperacute rejection and enhancement of mouse skin grafts by antibodies with a distinct specificity.

Pure 7S IgG2 was prepared from B6AF1 anti-B10.D2 ascites fluid by affinity chromatography. This preparation was extensively absorbed with B10.D2 red blood cells to remove the antibodies directed against the serologically defined antigens of the major histocompatibility complex. After absorption the serum had retained in vitro cytotoxic activity against 45 percent of B10.D2 spleen cells. The absorbed and unabsorbed 7S IgG2 antibodies were tested for their capacity to induce enhancement and, in the presence of rabbit complement, hyperacute rejection of B10.D2 skin grafts in B6AF1 recipient mice. The enhancing capacity of 7S IgG2 was completely unimpaired after absorption. However, the absorbed preparation was unable to induce hyperacute rejection of the grafts even if very high doses were administered. The results show that hyperacute rejection of skin grafts in this model is mediated by antibodies directed against the serologically defined antigens (i.e., H-2K antigens) of the H-2 complex. They further support the hypothesis that immunologic enhancement is mediated by antibodies directed against Ir-region-as-sociated antigens.