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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.

journal_name

Mol Immunol

journal_title

Molecular immunology

authors

Fukuchi Y,Sato M,Yamashita T,Koyama J

doi

10.1016/0161-5890(92)90194-3

subject

Has Abstract

pub_date

1992-05-01 00:00:00

pages

583-91

issue

eissn

0161-5890

issn

1872-9142

journal_volume

pub_type

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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.