Comparability of delayed hypersensitivity in various rodents: I. Regulatory mechanism of delayed footpad reactions in the hamster

Abstract

A relationship between delayed footpad reaction and antibody production was observed in hamsters immunized with erythrocytes of the mouse (MRC), sheep (SRC), or chicken (CRC). (i) In hamsters immunized with MRC in incomplete Freund's adjuvant (IFA), delayed reactions were positive in spite of high titers of IgM. Delayed reactions became negative with the appearance of IgG in hamsters pretreated with mouse spleen cells. (ii) In those immunized with SRC in IFA, positive delayed reactions were elicited only in the absence of IgG. Delayed reactions were converted from negative to positive by treatment with cyclophosphamide before elicitation in the presence of IgG. (iii) After immunization with SRC in complete Freund's adjuvant (CFA) or CRC in IFA or CFA, positive delayed reactions were elicited in the presence of IgG. There may exist an unstable form of delayed footpad reactions, which is regulated by antibody production, and a stable form, which is not regulated. Suppression in the former may be ascribed to some mechanism which is sensitive to cyclophosphamide and may be related to the production of IgG but not IgM.