Mechanisms Underlying the Suppression of Adjuvant‐Induced Arthritis by 6‐Mercaptopurine

Abstract

Daily oral administration of 6-mercaptopurine suppressed the development of the secondary (immune) lesions of adjuvant arthritis in a dose-related manner. The degrees of arthritis suppression corresponded closely to suppressions of concurrent development of the humoral and the cellular immune response to El₄ cells. A short course of therapy during the sensitization period (day — 1 to day 5 when the day of adjuvant injection is designated as day 0) appeared to be almost as effective as continued daily dosing (day —1 to day 15). The drug did not influence the development of the primary (nonimmune) lesions of adjuvant arthritis at all dosage levels investigated. Chronic pretreatment with 10 mg/kg/day PO for 17 days had no effect on the development of carrageenin–induced acute inflammation in the rat. The suppression of adjuvant arthritis by 6-mercaptopurine, unlike suppression by cyclophosphamide, appears to result primarily from its suppressive action on the immune response.