Similar activities of IgG1 and IgG2 alloantibodies in enhancement of mouse skin grafts and in opsonization

B6AF1 anti-B10.D2 ascites fluid was separated in highly purified IgG1 and IgG2 alloantibodies, which were concentrated to yield similar specific antibody activities on the basis of two-stage lymphocytotoxicity. Their similar specific activities were confirmed by flow cytometric analysis. When tested for enhancement of B10.D2 skin, grafted onto B6JAF1 recipients, and for the opsonization of 51Cr-labelled B10.D2 leukocytes, IgG1 antibodies were as effective as the IgG2 preparation. Therefore IgG1 and IgG2 antibodies have similar enhancing capacities. The close correlation with their opsonizing effect supports the hypothesis that interaction of the Fc-part of enhancing alloantibody with Fc-receptor bearing cells is involved in the induction of enhancement.