Complement receptors and phagocytosis.

Current understanding of the molecular mechanisms involved in regulating the phagocytic function of monocytes, macrophages and polymorphonuclear leukocytes is summarized, giving emphasis to the role of the phagocyte integrins of the CD11/CD18 family. New data relating to the hypotheses that optimal function of these receptors is a property of activated cells is discussed, with reference to possible signal transduction mechanisms leading to enhanced integrin function. Finally, a model is proposed for the involvement of CD11b/CD18 in cell functions when no ligand for this receptor is apparent.