Abstract

Histamine is involved in the execution of an immune reaction. Receptors for histamine, of which four different subtypes are known so far, are found on dendritic cells and on T cells. Via these receptors, histamine either indirectly or directly affects the activation of T cells. Data in the literature regarding the involved receptor subtypes and the mode of action of histamine on T cells are somewhat contradictory and depend on the type of cells analyzed, polarized T cells, or freshly prepared T cells within the context of the whole splenocyte population. Therefore, we analyzed the effect of histamine on murine T cells within splenocytes in a detailed manner. We stimulated freshly prepared splenocytes in the presence or absence of histamine with α-CD3 in vitro and analyzed the induced cytokine production. We show that histamine reduced the α-CD3-induced interferon-γ (IFN-γ) production of CD4⁺ cells via the histamine H₂-receptor. Moreover, the effect of histamine on the α-CD3-induced IFN-γ production could be transferred within conditioned splenocyte supernatants induced by histamine (in the absence of α-CD3). Thus, the histamine effect is mediated by a soluble factor, which, however, is neither of the classical anti-inflammatory mediators, interleukin-10, or transforming growth factor-β.