Histamine suppression of human lymphocyte responses to mitogens.

Exogenously added histamine in non-cytotoxic concentrations (10^?5?10^?3M) suppresses in vitro proliferation of lymphocytes induced by PHA or Concanavalin A. This suppressive effect was observed when histamine was present for as short as $\text{1}\text{2}$ hr in the beginning of the culture. Histamine, in concentrations as high as 10^?3M, did not cause increased release of isotope from ⁵¹Cr-labeled lymphocytes following 4 hr of incubation. The histamine H₂ receptor antagonist, metiamide, but not the H₁ receptor antagonists diphenhydramine or chlorpheniramine, blocked the histamine suppressive effect. Some of the biological implications of these findings are discussed.