title: Low ligand binding activities of two distinct types of Fc gamma receptor on guinea-pig peripheral blood polymorphonuclear leukocytes are differentially improved by proteolysis or platelet activating factor.
abstract: The expression and ligand binding activity of Fc receptors for IgG (Fc gamma R) on guinea-pig peripheral blood polymorphonuclear leukocytes (blood PMN) have been compared with those on casein-elicited peritoneal PMN (exudate PMN). Both the PMN were found to express two distinct types of Fc gamma R, one specific for IgG1 and IgG2 (Fc gamma 1/gamma 2 R) and the other for IgG2 alone (Fc gamma 2 R), when evaluated by their reactivity to monoclonal antibodies (mAb) directed against each type of Fc gamma R. The surface density of Fc gamma 1/gamma 2 R was not significantly different between the two cell types, whereas exudate PMN expressed five times as many Fc gamma 2 R as blood PMN. Moreover, IgG immune complex (IC) binding activities of both the Fc gamma R on blood PMN were markedly low as compared with those on exudate PMN. In addition, blood PMN could not significantly generate superoxide anion (O2-) when exposed to IC. However, these lower activities were improved by protease treatment of the cells or by incubation with platelet activating factor (PAF). Fc gamma 2 R on blood PMN was found to be sensitive to pronase, whereas Fc gamma 1/gamma 2 R was resistant. Pronase-treated blood PMN showed a marked IC binding activity, though they lacked Fc gamma 2 R. This activity was completely blocked by anti-Fc gamma 1/gamma 2 R mAb, indicating that the proteolysis augments the ligand binding capacity of Fc gamma 1/gamma 2 R. In contrast, PAF was found to specifically modulate Fc gamma 2 R. The Fc gamma 2 R expression was significantly increased within 5 min incubation with PAF, whereas that of Fc gamma 1/gamma 2 R was not affected. The cells also exhibited enhanced IgG2-IC binding and subsequent O2- generating activities. These results indicate that both the Fc gamma R on blood PMN are functionally immature and are converted to exhibit intrinsic activities by proteases and PAF; such changes may occur in vivo during exudation and at inflammatory sites.
authors.affiliation: Department of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Fukuchi
authors.forename: M
authors.initials: M
authors.lastname: Sato
authors.forename: T
authors.initials: T
authors.lastname: Yamashita
authors.forename: J
authors.initials: J
authors.lastname: Koyama
mesh_terms: D000818:Animals; D000936:Antigen-Antibody Complex / Q000378:metabolism; D000943:Antigens, Differentiation / Q000032:analysis* / Q000378:metabolism; D010450:Endopeptidases / Q000494:pharmacology*; D006168:Guinea Pigs; D007074:Immunoglobulin G / Q000378:metabolism*; D008297:Male; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism; D010972:Platelet Activating Factor / Q000494:pharmacology*; D011961:Receptors, Fc / Q000032:analysis* / Q000378:metabolism; D017452:Receptors, IgG; D013481:Superoxides / Q000378:metabolism
chemical_list: D000936:Antigen-Antibody Complex; D000943:Antigens, Differentiation; D007074:Immunoglobulin G; D010972:Platelet Activating Factor; D011961:Receptors, Fc; D017452:Receptors, IgG; D013481:Superoxides; D010450:Endopeptidases