Microfilament and microtubule function in human monocytes.

The functions of microfilaments and microtubules in human monocytes were examined by exposing peripheral blood monocytes to cytochalasin B, a microfilament inhibitor, and to colchicine, an antitubulin. Cytochalasin B, 10 microgram/ml, inhibited all monocyte functions tested: chemotaxis was reduced by 96% of control levels (p less than 0.01), random mobility by 88% (p less than 0.01), candidacidal activity by 57% (p less than 0.01), and phagocytosis by 34% (p less than 0.01). Monocyte adherence was also significantly reduced (by 65%). Colchicine, 10 microgram/ml, significantly reduced monocyte chemotaxis by 39% (p less than 0.01) and random mobility by 59% (p less than 0.01), but phagocytosis and candidacidal activity were not diminished at 0.1 to 100 microgram/ml. Monocyte adherence was modestly decreased (46%) by 10 microgram/ml of colchicine. Thus, cytochalasin B, a microfilament inhibitor, reduced all five functions tested. In contrast, colchicine, an antitubulin, inhibited only chemotaxis, random mobility, and adherence. These data suggest that in monocytes (1) microfilaments are the structural element of cell membrane and cytoplasm required for most cellular functions and (2) microtubules facilitate membrane surface interaction in chemotaxis, random mobility, and adherence.