CD44 promotes a serum-opsonin independent mechanism of phagocytosis of apoptotic neutrophils.

Abstract

<p>A) Monocyte-derived macrophages were incubated in the absence or presence of CD44 mAb for 30 min prior to addition CMFDA-labelled neutrophils that had been cultured either in human serum albumin (Albumin) or autologous serum (Serum). Assessment of phagocytosis was made by flow cytometry, data are mean ± SEM from 5 independent experiments. Although CD44 augmented phagocytosis relative to untreated cells (* = p<0.05), no significant differences between phagocytosis of PMN cultured in albumin versus serum was found following CD44 treatment. B) Glucocorticoid-treated monocyte-derived macrophages were incubated in the absence or presence of CD44 mAb for 30 min prior to addition CMFDA-labelled neutrophils that had been cultured in human serum albumin. Phagocytosis was assessed in the presence of 100 ng/ml of protein S for 30 min and the proportion of phagocytic macrophages determined by flow cytometry. Data shown are mean percentage phagocytosis ± SEM from 5 independent experiments. Although the presence of protein S augmented phagocytosis by glucocorticoid-treated macrophages (* = p<0.05), there was no significant difference between phagocytosis of PMN in the presence or absence of protein S following CD44 treatment.</p