On the Immunodepressive Effect of Rifampicin (RFP) on Cell-mediated Immunity of Guinea Pigs, Examined by Rabbit Red Blood Cell Rosette Formation Method

Abstract

Since Paunescu(1) reported the reversible immunosuppressive effect of RFP on cell-mediated immunity (CMI) of rabbit examined by delayed-type hypersensitivity, active supplementary trials have been carried out to examine whether the suppressive action of this important medicament mainly found by the use of experimental animals has a significant meaning in treatment of patients by this drug(2-7). The divergence of their opinions has been derived from two causes, that is, 1) the dosage of RFP is influential on its suppressive effect, and 2) the dosage usually received by patients is enough high as that necessitating a consideration for its suppressive effect or not(4,6).Since the usual dosage of RFP for antileprosy chemotherapy is 10 mg/kg or less and is at least not higher than that for treatment of tuberculosis patients to whom 15-10 mg/kg are given as usual dosages by daily dose or 25-15 mg/kg by intermittent method, we felt a necessity to elucidate a question whether the suppressive effect of RFP can be found even at the dosage of low level such as 10 mg/kg which corresponds to the half dosage of RFP hitherto accustomed to be used for animal experiments in tuberculosis field.On the other hand, we reported recently the influences by high dosages of DDS or B 663 (10-100 mg/kg or 30 mg/kg, respectively) on the immunological states of experimental animals(8). As B 663 is a drug of ultra-accumulative, we presumed that the final tissue concentration of this drug after a series of doses may gradually reach to a possible definite level by equilibrium between saturation to various tissues and elimination from the tissues and humors. However, as for the dosages of DDS examined in the foregoing experiments, we felt the necessity for a supplementary trial because the usual dosage of DDS in treatment of patients is below 5 mg/kg.In addition, in order to establish the usage of a favorable method for examining CMI of guinea pigs by the formation of rosette cells between guinea pig lymphocyte (GPL) and rabbit red blood cells (RRBC method)(8,9), the additional investigations were requested concerning the reliability and the further improved facility of this method.Since the preceding reports indicated that the main suppressive effect of RFP was found on CMI and not on humoral immunity(3,5), we attempted the three experiments by RRBC method to elucidate these questions.