Effect of histamine on chemotaxis and phagocytosis of human alveolar macrophages and blood monocytes.

We studied in vitro the effect of histamine on the chemotactic and phagocytic abilities of human blood monocytes and alveolar macrophages. The chemotactic response to activated autologous serum, leukotriene B4 or N-formyl-methionine-L-phenylalanine was similar for macrophages and monocytes. Incubation of monocytes with histamine in picomolar concentrations caused a significant chemotactic inhibition (about 25%). This effect was antagonized by cimetidine but not by promethazine. Histamine did not have an effect on alveolar macrophages chemotaxis or phagocytosis. Thus, histamine, in minute concentrations, exerts, in vitro, a partial inhibitory effect on monocyte chemotaxis through activation of H2-type receptors.