"Immunoregulatory effects of cimetidine: inhibition of suppressor cell effector function in vivo".

The effects of cimetidine upon suppressor cell effector function in a well-studied murine model of contact hypersensitivity were examined. Intravenous inoculation of BALB/c mice with DNP-coupled syngeneic spleen cells induced the production of DNP-specific suppressor cells which was demonstrated by a reduction in ear swelling after contact sensitization with 1-fluoro-2, 4-dinitrobenzene (DNFB) following transfer of spleen and lymph node cells to naive syngeneic recipients. Cimetidine treatment of mice who had also received suppressor cells eliminated the manifestation of suppressor cell activity as measured by the development of normal immunologic response following contact sensitization with DNFB. While all the groups receiving cimetidine showed restoration of delayed hypersensitivity, the maximum effect was seen when 50 mg/kg of cimetidine was administered on Day 5 (day of challenge). These results indicate that, in addition to its previously described inhibitory role in suppressor cell induction, cimetidine is also capable of inhibiting suppressor cell effector function. The involvement of histamine in both these processes in vivo is also suggested.