Tumor necrosis factor-induced degranulation in adherent human neutrophils is dependent on CD11b/CD18-integrin-triggered oscillations of cytosolic free Ca2+.
We have recently been able to correlate closely the "spontaneous" oscillatory activity of cytosolic free Ca2+ in adherent human neutrophils with the ability of tumor necrosis factor (TNF) to induce secretion of granule proteins from these cells. In the present work we show with a single-cell technique that preincubation of human neutrophils with antibodies to CD18, the common beta chain of leukocyte adhesion proteins, inhibits TNF-induced secretion of lactoferrin in a time- and concentration-dependent manner. Similar effects of CD18 antibodies were found on chemotactic factor (fMet-Leu-Phe)- but not on phorbol 12-myristate 13-acetate-induced secretion, suggesting that cell-surface-receptor-mediated secretion is dependent on integrin-associated signals. Similarly, antibodies to CD11b (alpha chain of macrophage 1) also inhibited TNF- and fMet-Leu-Phe- but not phorbol 12-myristate 13-acetate-stimulated release of lactoferrin. Antibodies to CD11a (alpha chain of lymphocyte function-associated antigen 1) or CD11c (alpha chain of p150,95) had only a minimal effect on agonist-induced secretion. Data obtained in several laboratories, including our own, made us suspect that integrin interaction with the surface is responsible for the oscillatory activity of cytosolic free Ca2+ in adherent cells. Indeed, preincubation with antibodies to either CD18 or CD11b, but not to CD11c, inhibited the oscillations of cytosolic free Ca2+ in adherent neutrophils. This inhibitory effect was evident both as a reduction of the number of responding cells and as a reduction of the oscillatory activity in the cells. In conclusion, the oscillatory activity of cytosolic free Ca2+ in adherent neutrophils is mediated through the CD18/CD11b integrins. The generation of this Ca2+ signal may explain how adherence, by way of the integrins, changes the functional properties of the cell and enables TNF to induce secretion.
Richter
J
J
Department of Medicine, University Hospital, Lund, Sweden.
Ng-Sikorski
J
J
Olsson
I
I
Andersson
T
T
D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000276:immunology*; D018821:CD18 Antigens; D002118:Calcium / Q000097:blood*; D003600:Cytosol / Q000378:metabolism; D006462:Hemolytic Plaque Technique; D006801:Humans; D066298:In Vitro Techniques; D016023:Integrins / Q000502:physiology*; D007700:Kinetics; D016177:Macrophage-1 Antigen / Q000276:immunology*; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D009991:Oscillometry; D016028:Receptors, Leukocyte-Adhesion / Q000276:immunology*; D011994:Recombinant Proteins / Q000494:pharmacology; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018821:CD18 Antigens; D016023:Integrins; D016177:Macrophage-1 Antigen; D016028:Receptors, Leukocyte-Adhesion; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D002118:Calcium