Abstract: | Rabbits were immunized against purified proteins, tissue extracts or sheep erythrocytes, with or without Freund's adjuvant. Skin reactions of the delayed type were found only in animals given antigen with adjuvant, although all rabbits developed serum antibodies and most of them Arthus type reactions. Lymphocytes of all animals, however, showed similar transformation activity when cultured with the immunizing antigen. Thus the blast transformation phenomenon correlates well with both cellular and humoral immune responses and not with the delayed type hypersensitivity only. |