Suppressor T lymphocytes possess histamine2 (
H2) receptors and contribute significantly to the function of the immune system. Experimentally,
cimetidine, an H2-receptor antagonist, has been shown to enhance a variety of immunologic functions both in vivo and in vitro because of its inhibitory effects on suppressor-cell function. Successful
tumor immunotherapy, as well as some protection from
infection, has been reported in experimental animals. Patients receiving
cimetidine have been shown to exhibit enhanced cell-mediated immunity as evaluated by increased response to skin-test
antigens, restoration of sensitivity following development of acquired tolerance, and increased responses of lymphocytes to
mitogen stimulation. Preliminary reports also indicate that
cimetidine may offer therapeutic benefits for patients with
Varicella zoster and
Herpes simplex infections, as well as those suffering from mucocutaneous
candidiasis and
common variable hypogammaglobulinemia. These immunoregulatory effects are dose-related but are not always consistent. Because of its inhibitory effect on suppressor function,
cimetidine treatment may be deleterious in patients with organ transplant and autoimmune disorders.
Cimetidine should be used as an
immunomodulator on an experimental basis only.