Histamine-induced inhibition of normal human basophil chemotaxis to C5a.

Histamine in concentrations as low as 10(-8) M inhibited the chemotactic response of normal human basophils to C5a. Histamine had no effect on basophil chemotaxis to lymphocyte-derived chemotactic factor. Histamine inhibition of basophil chemotaxis to C5a was prevented by metiamide, a drug which blocks H2 receptors for histamine. Since the accumulation of basophils in delayed cutaneous basophilic hypersensitivity (CBH) reactions may occur in part because of chemotaxis to C5a, and since C5a can induce histamine release, histamine inhibition of chemotaxis may limit basophil infiltration in CBH lesions.