Immunological responsiveness of tuberculosis patients receiving rifampin

Rifampin has been shown to impair both humoral and cell-mediated immune responses in animal models. In order to detect a similar effect in man, 11 patients with active tuberculosis were evaluated before, 2 weeks after, and 12 to 16 weeks after initiating rifampin. Several parameters were serially measured including blood lymphocytes, intradermal response to intermediate strength tuberculin (PPD), and in vitro proliferative responses to phytohemagglutinin (PHA), a nonspecific mitogen, and to the specific antigens, PPD and influenza A. No changes in lymphocyte counts were noted. No changes in response were noted 2 weeks after beginning treatment with rifampin. However, compared with initial and 2-week responses, the PHA response was reduced by 47%, the PPD by 68%, and the influenza by 75%, and 6 of 11 patients showed no induration after tuberculin skin testing at the 12- to 16-week point. These results indicate that in doses employed for the treatment of tuberculosis, rifampin has an immunosuppressive effect in man that develops gradually.