Human lung macrophages induce histamine release from basophils and mast cells

Human lung macrophages isolated from surgical specimens, when cultured for 24 h, acquired the capacity to induce histamine release from human basophils. This releasing activity was entirely accounted for by soluble, nondialyzable factor(s) (molecular weight, more than 2,000 daltons) released from cultured macrophages. The basophil release reaction was dose-dependent, and also Ca⁺⁺ (optimal concentration = 5 mM) and temperature (optimal = 37° C) dependent. Supernatants derived from the equivalent of 3 x 10⁶ macrophages /ml released 50% histamine from basophils of sensitive donors. The supernatants also induced histamine release from lung mast cells. These results are the first report of a human macrophage-derived product that activates basophils and mast cells to release histamine.