Polymorphonuclear neutrophils in saliva and blood: a comparative study of morphology, function and phenotype

The morphology, phagocytic activity, production of hydrogen peroxide (H2O2) and expression of lymphocyte function-associated antigen-1 (LFA-1; CD11a/CD18), complement receptor type 3 (CR3; CD11b/CD18), p150,95 (CD11c/CD18), and platelet/endothelial cell adhesion molecule-1 (PECAM-1; CD31) by oral polymorphonuclear neutrophils (PMN) are assessed and the results compared with those of blood PMN. There were no differences in the morphology and phagocytic activity between oral and blood PMN. H2O2 production was measured following stimulation with phorbol myristate acetate (PMA) and N-formyl-L-leucyl-L-phenylalanine (FMLP) as indicators of bactericidal activity. There was a significant difference in the H2O2 production by the two groups when stimulated with FMLP; the level of H2O2 production by oral PMN was significantly higher than that by blood PMN. However, there was no significant difference in H2O2 production between oral and blood PMN when stimulated with PMA. The percentage of CD11a- and CD11c-positive concentrated oral PMN was significantly lower than that seen in blood PMN, as was the percentage of CD31-positive cells. Higher H2O2 production by oral PMN following stimulation with FMLP may result in enhanced bactericidal activity. Low expression of CD31 may lead to the accumulation of PMN in the mouth by blocking their return to the bloodstream. These phenomena may be necessary for oral PMN to protect periodontal tissues from bacteria in the mouth.