IMMUNOSUPPRESSIVE ACTIVITY OF ALLOGENEIC ANTI-LYMPHOCYTE SERUM IN RAT

Allogeneic anti-rat lymphocyte serum (IALS) was prepared by immunization of Wistar-Furth inbred rats with lymph node and spleen cells of Lewis inbred rats and compared with rabbit anti- Lewis rat lymphocyte serum (RARLS). In contrast to RARLS, IALS contained cytotoxins of allogeneic, rather than species, specificity as shown by direct test against lymphocytes of various inbred rat strains and by cytotoxin absorption tests. IALS absorbed with cells of the Buffalo strain retained cytotoxins for Lewis and Fischer (AgB1), the ability to produce anemia and lymphopenia in vivo, as well as the ability to delay rejection of rat allogeneic heart grafts in Lewis recipients. RARLS absorbed with rat cells of any origin did not retain any in vitro or in vivo activity. It was concluded that the activity of such absorbed IALS was the result of specific attachment of anti-AgB1 antibodies to AgB1 lymphocytes, and that concentration and availability of antigen is responsible for IALS and, by analogy, RARLS, immunosupprcssive action. © 1969 by The Williams and Wilkins Co.