title: Influence of extracellular Ca2+ and Mg2+ on chemotactic factor-induced neutrophil aggregation.
abstract: The influences of extracellular Ca2+ and Mg2+ on chemotactic factor-induced rabbit polymorphonuclear neutrophil (PMN) aggregation was studied using a recently described Coulter counter assay technique. Compared with those of other PMN functional assays (adhesion, chemotaxis, degranulation, and phagocytosis), the cation requirements for cell aggregation appear unique. Chemotactic factor-induced aggregation did not occur in the absence of either cation. When the concentration of both cations was increased equivalently, aggregation increased. The effect plateaued at 2.8 mM of Ca2+ and Mg2+. When the concentration of one cation alone was increased, aggregation peaked. Further increases inhibited maximal aggregation. By systematic variation of the cation concentrations, optimal aggregation was found at Ca2+ and Mg2+ concentrations of 2.8 mM. At these concentrations, significant aggregation was induced with chemotactic doses of bacterial factor, the chemotactic fragment of human C5, and the synthetic chemotactic tripeptide, formyl-met-leu-phe. Thus, under these conditions, chemotactic factor-induced aggregation of neutrophils may be a useful indicator of interactions of chemotactic factors with neutrophils.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002449:Cell Aggregation / Q000187:drug effects; D002634:Chemotaxis, Leukocyte / Q000187:drug effects*; D003182:Complement C5 / Q000494:pharmacology; D004926:Escherichia coli; D006023:Glycoproteins / Q000494:pharmacology*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects*; D009842:Oligopeptides / Q000494:pharmacology; D011817:Rabbits
chemical_list: D003182:Complement C5; D006023:Glycoproteins; D009842:Oligopeptides; D008274:Magnesium; D002118:Calcium