Effects of variation in time and dose of cyclophosphamide injection on delayed hypersensitivity and antibody formation

Abstract

A single injection of Cyclophosphamide (CY) in a dose of 300 mg of CY/kg of mice resulted in enhanced delayed hypersensitivity (DH) when administered between at least 7 days prior to and 15 days after intracutaneous (ic) immunization of sheep red blood cells in Freund's complete adjuvant. The maximal enhancement occurred when CY was applied 8 hr before the antigen. Using the latter interval, the effect of varying the dose of CY before ic or intraperitoneal (ip) injections of antigen was studied. Combined with ic immunization, increasing doses of CY resulted in increasing DH. The ip route of immunization needed CY in amounts of at least 100 mg/kg to augment DH to a detectable level. The enhancing effect of lower doses of CY was more pronounced when the interval between immunizing and eliciting injections was reduced. Administration of 300 or 200 mg of CY/kg before ip immunization suppressed the antibody formation, when measured S and 7 days later. A dose of 100 mg of CY/kg caused a suppression of antibody formation on Day 5, but an enhancement on Day 7. With this dose, a maximal enhancement of DH was found on both days. The results suggest that CY interferes with more than one regulatory mechanism of the immune response.