Modulation of adhesion molecule profiles on alveolar macrophages and blood leukocytes

Background: Cell adhesion molecules are believed to be essential for blood cell recruitment to the lung and for the movement of alveolar macrophages (AM) within the lung. Objective: To investigate the expression pattern of L-selectin and beta(2) integrins on blood leukocytes and AM, including AM of various maturity. Methods: Flow cytometry was used to study the expression of L-selectin (CD62L) and of the beta(2) integrins CD11a, CD11b, and CD11c on AM (including density-defined subpopulations), monocytes (Mo), polymorphonuclear neutrophils (PMN) and lymphocytes (Ly) sampled from healthy individuals, during incubation with and without lipopolysaccharide (LPS). Results: A significantly different modulation pat tern of beta(2) integrins and L-selectin was demonstrated on Mo and AM, cells of the same differentiation lineage. In contrast to AM, Mo had a marked ability to respond to LPS stimulation by increased expression of CD11a, CD11b and CD11c and decreased expression of L-selectin. These molecules were expressed to a similar degree on AM, whereas the basal levels of CD11b and L-selectin were considerably higher on Mo than on AM. A significantly different expression of CD11a as well as differences in the regulation of L-selectin during incubation were also demonstrated between density-defined subpopulations of AM. CD11a could not be upregulated on PMN, otherwise the modulation patterns of CD11b, CD11c and L-selectin were similar to that on Mo. The expression of CD11a on Ly was 3- to 6-fold higher than on Mo, PMN and AM. The level of CD11b decreased significantly upon incubation (uninfluenced by LPS stimulation), and CD11c was hardly expressed on Ly. The level of L-selectin on Ly was higher than on Mo, AM and PMN and was not decreased during incubation. Conclusion: Developmental origin, degree of cell differentiation (maturity) as well as different environmental conditions all heavily influence the expression and modulation pattern of beta(2) integrins and L-selectin on leukocytes and Mo-derived AM. Copyright (C) 1999 S. Karger AG, Basel.