Leukocyte adhesion-deficient neutrophils fail to amplify phagocytic function in response to stimulation. Evidence for CD11b/CD18-dependent and -independent mechanisms of phagocytosis.
Stimulation of PMN with inflammatory mediators markedly augments Fc and CR1 receptor-mediated ingestion. However, CD11/CD18-deficient PMN from three patients with complete leukocyte adhesion deficiency (LAD) failed to recruit phagocytic function in response to phorbol esters, cytokine, or Arg-Gly-Asp-containing ligand stimulation. Because stimulated ingestion is protein kinase C (PKC)-dependent, our data indicate that LAD PMN exhibit only PKC-independent phagocytosis. The defect in PKC-dependent ingestion is specific for CD11b/CD18 and not secondary to the chronic or recurrent infections which occur in this disease. The LAD phenotype for phagocytic function can be reproduced in normal PMN by the anti-CD11b MAbs OKM1 and OKM10. In contrast, MAb Mo1 (anti-CD11b) and MAb IB4 (anti-CD18) inhibit both CD11b/CD18-dependent and -independent mechanisms of ingestion by normal PMN. Their ability to inhibit CD11b/CD18-independent ingestion may be mediated by cAMP, as shown by experiments with a protein kinase A inhibitor HA1004 and by direct measurement of cAMP levels in immune complex- and FMLP-stimulated PMN. These data indicate that CD11b/CD18-independent and -dependent mechanisms of phagocytosis exist and that some effects of anti-CD11b/CD18 MAbs may be mediated by alterations in cAMP levels.
Department of Pharmacology, University of Missouri-Columbia 65212.
H D
HD
Gresham
I L
IL
Graham
D C
DC
Anderson
E J
EJ
Brown
D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000502:physiology*; D018821:CD18 Antigens; D015935:Complement C4b / Q000276:immunology; D006105:Granulomatous Disease, Chronic / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D018370:Leukocyte-Adhesion Deficiency Syndrome; D016177:Macrophage-1 Antigen / Q000502:physiology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000276:immunology*; D010587:Phagocytosis; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology; D011494:Protein Kinases / Q000502:physiology
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018821:CD18 Antigens; D007074:Immunoglobulin G; D016177:Macrophage-1 Antigen; D015240:Phorbol 12,13-Dibutyrate; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015935:Complement C4b; D011494:Protein Kinases; D011493:Protein Kinase C