Preferential development by mice of delayed hypersensitivity to purified basic proteins

Abstract Mice injected with purified protein antigens (e.g., serum albumins) in incomplete Freund adjuvant develop both Arthus and delayed hypersensitivities. The presence of the former interferes with observation of the latter. But mice similarly injected with methylated derivatives of such purified proteins preferentially develop delayed hypersensitivity. Hence the latter can be studied independently of a preceding Arthus reaction. Such use of methylated serum albumins in the experiments reported here showed that polymorphonucleocytes outnumber monocytes early in specific delayed hypersensitivity skin reactions but later are replaced by large numbers of monocytes, that passive transfer of delayed hypersensitivity may require cooperation between lymphoid cells and humoral antibody, and that immediate and delayed hypersensitivities in mice can be distinguished from each other by differences in antigenic determinant sites. Methylated serum albumins are easy-to-prepare basic proteins which are readily soluble at acid but not alkaline pH.