Immunomodulating influence of active metabolite of cyclophosphamide on human lymphocyte immunoglobulin biosynthesis in vitro.

4-hydroxycyclophosphamide (4HCy) inhibits T cell-dependent and direct B cell humoral responses of human lymphocytes in vitro, but causes a potentiation of the former in the lowest drug concentrations. Lymph node humoral responses are strongly sensitive, but those of spleen are relatively resistant to the drug. Although the induction of suppressor T cells is Cy-resistant, the expression of their function is sensitive. The suppressor cell function of antibody production appears to be more sensitive than the helper function.