Regulation of secondary antibody responses in rodents I. POTENTIATION OF IgG PRODUCTION BY CYCLOPHOSPHAMIDE.

This paper describes the effects of a single dose of cyclophosphamide on specific IgG production in rats during an established secondary immune response. (PVG × Agus)F₁ rats were immunized twice (days 0 and 28) with chicken erythrocytes (CRBC), received cyclophosphamide (100 mg/m² of body surface area) on day 33 and were killed 8 days later. The production of anti-CRBC IgG antibodies was assessed by testing the supernatants of spleen cell cultures in a cytotoxicity assay with ⁵¹Cr-labelled CRBC as target cells and normal rat spleen cells as effector cells. In observations of fifty-nine pairs of treated and untreated rats from eight separate experiments, the administration of cyclophospharnide resulted in: (1) a decrease in the number of spleen cell to a median of 108.63 from a median of 10^8.7 (P < 0.0025); (2) an increase in the anti-CRBC IgG antibody titre of the supernatants of cultured spleen cells to a median of 10^0.67 from a median of 10^0.27 (P < 0.0025); and (3) the calculated anti-CRBC IgG antibody production per spleen to be increased in the drug-treated rats to a median of 10^2.26 from a median of 10^2.0 (P < 0.005). In a cyclophosphamide dose-response study, it was shown that some enhancement of antibody production was induced by doses between 12.5 and 50 mg/m² and consistently elevated levels of antibody production were associated with doses between 100 and 400 mg/m². [ABSTRACT FROM AUTHOR]