Effects of cyclophosphamide on the expression and induction of delayed hypersensitivity.

Erythematous delayed reactions without induration, presumably assigned to Jones-Mote type, were characterized by the resistance to treatment with cyclophosphamide (CY) before elicitation or immunization in guinea pigs immunized with BGG in IFA or CFA. CY-treatment before elicitation converted delayed erythematous reactions from negative to positive at late intervals after immunization with BGG in IFA. Such a treatment augmented erythematous delayed reactions in animals immunized with BGG in CFA, but abolished induration at the reaction sites. CY-treatment before elicitation or immunization reduced the numbers of basophils at the reaction sites, although erythematous delayed reactions were augmented. Effector T cells responsible for delayed erythematous reaction without induration appear to persist for a long period of time after immunization in the presence of antibody production or tuberculin hypersensitivity and the expression of their function may be inhibited by suppressive mechanisms.