DIFFERENT PATTERNS OF DEACTIVATION OF CHEMOTAXIS AND HAPTOTAXIS OF HUMAN PERIPHERAL-BLOOD MONONUCLEAR LEUKOCYTES BY SOLUBLE AND SURFACE-BOUND ATTRACTANTS

Soluble mediators and inducible cell-surface and matrix-bound molecule s coordinate the cascade of events giving rise to leukocyte emigration . Knowledge of the specific mechanisms underlying the attraction of ce lls into a local site, however, remains sketchy. In particular, it is unclear how chemoattractants cause rapidly moving immune cells to adhe re to the blood. vessel wall and to enter tissues. Here we show that t he neuroendocrine human growth hormone, a chemoattractant for monocyte s and lymphocytes in vitro, promotes haptotaxis, the migration of the cells induced by surface-bound gradients. Combination of soluble growt h hormone with soluble attractants, RANTES or formyl peptide, deactiva tes the migratory responses, as do combinations of surface-bound growt h hormone with surface-bound RANTES or formyl peptide. In contrast, ex posure of mononuclear leukocytes to combinations of soluble chemotacti c with surface-bound haptotactic gradients of attractants does not dea ctivate migration. The findings suggest that growth hormone may act as haptotactic agent, on the one hand, and that soluble attractants do n ot appear to affect haptotaxis when acting in concert with a surface-b ound attractant, on the other. This observation may have implications for the differential regulation of leukocyte accumulation in the vesse l wall at systemic and local sites.