Functional aspects of the selective depletion of lymphoid tissue by cyclophosphamide.

The increased intensity and prolongation of contact hypersensitivity reactions in animals treated 3 days prior to sensitization with 300 mg/kg cyclophosphamide (CY) has been investigated. No evidence has been found of increased activity of lymphoid tissue or non-specific skin reactivity following CY treatment. However there was evidence of normal T-lymphocyte function associated with reduced B-lymphocyte function. Partial reconstitution could be obtained by transplanting spleen and the effect of CY treatment could be partially reproduced by splenectomy following sensitization. It is suggested that a B-lymphocyte response to soluble antigen modulates a normal cell-mediated immune response during the development of chemical contact sensitivity in the healthy animal and that this could be blocked completely by treatment with CY prior to sensitization or partially by splenectomy after sensitization.