ABSENCE OF SERUM BLOCKING ACTIVITY IN MICE IMMUNOLOGICALLY TOLERANT TO SOLUBLE HISTOCOMPATIBILITY-2 ANTIGENS

Abstract

B10.D2 mice receiving BIO.A bone marrow cells at birth are operationally tolerant as adults to BIO. A skin allografts. Scrum from such “allograft-tolerant” mice specifically inhibits or “blocks” the cytoloxic effect of immune lymphocytes when tested in an in vitro microcytotoxicity assay. By contrast, BIO.1)2 mice inoculated at birth with a partially purified, papain-solubilized alloantigen preparation derived from the spleens of A/J mice reject skin allografts in a normal fashion, but are unable to form specific alloantibody. Serum from such “antibody-tolerant” mice does not block lymphocyte-mediated cytotoxicity in vitro. These observations are compatible with the hypothesis that the serum factors which inhibit (or block) specific allograft immunity in vitro may be required for the induction and maintenance of tolerance to skin allografts.