We studied the effects of histamine on human immunoglobulin (IgE) and IgG4 production. Histamine selectively enhanced IgE and IgG4 production in purified surface IgE and IgG4 negative (sIgE(-)sIgG4(-)) B cells from normal donors stimulated with interleukin (IL)-4 plus anti-CD58 or IL-13 plus anti-CD58 monoclonal antibody (mAb) without affecting production of IgG1, IgG2, IgG3. IgM, IgA1, or IgA2. In cultures with IL-4 plus anti-CD58 mAb, histamine-induced enhancement of IgE and IgG4 production was specifically blocked by thioperamide (H-3 receptor antagonist), and was inhibited by anti-IL-10 antibody (Ab). In contrast, in cultures with IL-13 plus anti-CD58 mAb, histamine-induced enhancement was blocked by dimaprit (H-1 receptor antagonist), and was inhibited by anti-IL-G mAb. Histamine also enhanced IgE and IgG4 production by in vivo-generated sIgE(+) and sIgG4(+) B cells, respectively, from atopic patients; enhancement was blocked by dimaprit and thioperamide, and was inhibited by anti-IL-6 mAb and anti-IL-10 Ab. In sIgE(-)sIgG4(-) B cells, IL-4 plus anti-CD58 mAb induced IL-10 production and IL-10 receptor expression, whereas IL-13 plus anti-CD58 mAb induced IL-6 production and IL-6 receptor expression. Histamine increased IL-10 and IL-G production without affecting IL-10 and IL-6 receptor expression, in cultures with IL-4 plus anti-CD58 mAb and with IL-13 plus anti-CD58 mAb. respectively, which was blocked by thioperamide and dimaprit, respectively. In contrast, sIgE(+) and sIgG4(+) B cells spontaneously produced both IL-6 and IL-10 and constitutively expressed IL-6 and IL-10 receptors, and histamine increased IL-6 and IL-10 production without affecting IL-6 or IL-10 receptor expression, which was blocked by thioperamide and dimaprit. These results indicate that histamine enhanced IgE and IgG4 production by increasing endogenous IL-6 and IL-10 production via H-1 and H-3 receptors, respectively.