EFFECT OF MECHANICAL DEFORMATION ON STRUCTURE AND FUNCTION OF POLYMORPHONUCLEAR LEUKOCYTES

The present studies were designed to test the hypothesis that mechanic al deformation of polymorphonuclear leukocytes (PMN) leads to function al changes that might influence their transit in the pulmonary capilla ries. Human leukocytes were passed through 5- or 3-mu m-pore polycarbo nate filters under controlled conditions. Morphometric analysis showed that the majority of PMN were deformed and that this deformation pers isted longer after filtration through 3-mu m filters than through 5-mu m filters (P < 0.05) but did not result in the cytoskeletal polarizat ion characteristic of migrating cells. Flow cytometric studies of the filtered PMN showed that there was a transient increase in the cytosol ic free Ca2+ concentration after both 3- and 5-mu m filtration (P < 0. 01) with an increase in F-actin content after 3-mu m filtration (P < 0 .05). Although L-selectin expression on PMN was not changed by either 5- or 3-mu m filtration, CD18 and CD11b were increased by 3-mu m filtr ation (P < 0.05). Priming of the PMN with N-formyl-methionyl-leucyl-ph enylalanine (0.5 nM) before filtration resulted in an increase of CD11 b by both 5 (P < 0.05)- and 3-mu m (P < 0.01) filtration. Neither 5- n or 3-mu m filtration induced hydrogen peroxide production. We conclude that mechanical deformation of PMN, similar to what occurs in the pul monary microvessels, induces both structural and functional changes in the cells, which might influence their passage through the pulmonary capillary bed.