Sequential chemotactic and phagocytic activation of human polymorphonuclear neutrophils.
Human polymorphonuclear neutrophils (PMN) chemotax to a foreign entity. When the chemoattractants' origins are reached, specific receptors bind to the invader's surface, initiating phagocytosis, phagosome formation, and fusion with granule membranes, generating the bactericidal oxidative burst, and releasing lytic enzymes, specific peptides, and proteins. We explored the initial signaling involved in these functions by observing naïve, unprimed PMN in suspension using fluorescent indicators of cytoplasmic signals (Delta[Ca(2+)](i) and DeltapH(i)) and of bactericidal entities (oxidative species and elastase) exposed to N-formyl-methionyl-leucyl-phenylalanine (fMLP) and/or multivalent immune complexes (IC). fMLP and IC each initiate a rapid transient rise in [Ca(2+)](i), mostly from intracellular stores, simultaneously with a drop in pH(i); these are followed by a drop in [Ca(2+)](i) and a rise in pH(i), with the latter being due to a Na(+)/H(+) antiport. The impact of a second stimulation depends on the order in which stimuli are applied, on their dose, and on their nature. Provided that [Ca(2+)](i) is restored, 10(-7) M fMLP, previously shown to elicit maximal Delta[Ca(2+)](i) but no bactericidal functions, did not prevent the cells' responses with Delta[Ca(2+)](i) to a subsequent high dose of fMLP or IC; conversely, cells first exposed to 120 mug/ml IC, previously shown to elicit maximal Delta[Ca(2+)](i) and bactericidal functions, exhibited no subsequent Delta[Ca(2+)](i) or DeltapH(i) to either stimulus. While exposure to 10(-7) M fMLP, which saturates the PMN high-affinity receptor, did not elicit bactericidal release from these naïve unprimed PMN in suspension, 10(-5) M fMLP did, presumably via the low-affinity receptor, using a different Ca(2+) source.
Herrmann
Jens Martin
JM
Department of Biochemistry, Boston University School of Medicine, 80 East Concord Street, Boston, MA 02118, USA.
Bernardo
John
J
Long
Heidi J
HJ
Seetoo
Kurt
K
McMenamin
Mary E
ME
Batista
Eraldo L
EL
Van Dyke
Thomas E
TE
Simons
Elizabeth R
ER
D000936:Antigen-Antibody Complex / Q000276:immunology; D002118:Calcium / Q000032:analysis; D002634:Chemotaxis, Leukocyte; D003593:Cytoplasm / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000276:immunology; D018375:Neutrophil Activation / Q000502:physiology*; D009504:Neutrophils / Q000737:chemistry / Q000276:immunology*; D010196:Pancreatic Elastase / Q000032:analysis; D010587:Phagocytosis; D017382:Reactive Oxygen Species / Q000032:analysis; D017452:Receptors, IgG / Q000276:immunology
D000936:Antigen-Antibody Complex; D017382:Reactive Oxygen Species; D017452:Receptors, IgG; D009240:N-Formylmethionine Leucyl-Phenylalanine; D010196:Pancreatic Elastase; D002118:Calcium