DIFFERENCES IN ALTERED EXPRESSION OF L-SELECTIN AND MAC-1 IN MONOCYTES AND NEUTROPHILS

We have measured the altered expression of the adhesion-promoting gluc oproteins L-selectin and Mac-1 on monocytes and neutrophils after incu bation with different concentrations of the chemotactic factor FMLP. W e found a time- and dose-related down-regulation of L-selectin on both monocytes and neutrophils, which was more pronounced on neutrophils a s compared to monocytes at both low (10(-12) M) and high (10(-7) M) co ncentrations of the chemotactic factor FMLP. Presence of human albumin reduced the down-regulation of L-selectin on both monocytes and neutr ophils but to a greater extent on monocytes. Mac-1 expression increase d in a time and dose-dependent manner on both monocytes and neutrophil s when they were incubated with both low (10(-12) M) and high (10(-7) M) concentrations of FMLP, but the expression was more pronounced on n eutrophils. The up-regulation of Mac-1 was equally reduced by albumin on monocytes and neutrophils. Presence of EDTA in RPMI medium reduced the FMLP-induced down-regulation of L-selectin on both monocytes ad ne utrophils, indicating that the down-regulation of L-selectin is partly divalent cation dependent. Differences in the altered expression of L -selectin and Mac-1 in monocytes and neutrophils with sustained expres sion of L-selectin on monocytes can contribute to the sequential recru itment of these cells into an inflammatory site.