The effect of cyclophosphamide pretreatment on B-cell stimulation: dissociation of action on homocytotropic antibody and other B-cell functions.

A study has been made of the effect of cyclophosphamide (CY), given 3 days before immunization, on the development of homocytotropic antibody detectable by passive cutaneous anaphylaxis (PCA). A comparison of the effect on PCA antibody was made with the effect of haemagglutinating antibody and delayed hypersensitivity, which have been described previously. The effect of CY pretreatment in suppressing the PCA antibody response depended on the antigen used. There was little or no correlation between the production of antibody detectable by PCA and that detectable by passive haemagglutination. The level of PCA antibody was increased in certain systems by CY pretreatment. However, there was no parallelism with the systems in which haemagglutinating antibody was increased. It was concluded that the B-cell precursors of plasma cells making homocytotropic antibody, haemagglutinating antibody, antibody involved in the Arthus reaction and those modulating T-cell function in certain delayed type hypersensitivity reactions, belonged to populations with different susceptibilities to CY. In studies comparing the response to different doses of CY using ovalbumin as antigen, very little difference was found on the populations of B-cells modulating delayed hypersensitivity and those producing antibody.