The tissue distribution of human IgG Fc receptors (FcyRs) classified in three clusters of differentiation (CD16, using 5 antibodies, CD32, using 2 antibodies; and CD64, using 3 antibodies) was evaluated by immunohistochemistry on lymphoid (lymph node, spleen, thymus, tonsil) and non-lymphoid (heart, jejunum, kidney. liver, lung, muscle, stomach, and skin) tissues. Macrophage-like cells, including Kupffer cells, expressed all three classes of FcyR. Part of the cells coexpressed HLA-DR. lnterdigitating dendritic cells that were present in high density in interfollicular areas of a lymph node showing dermatopathic lymphadenopathy were immunoreactive for CD32, but not for CDI 6 or CD64 antibodies. In lymphoid tissue, mantle zones of secondary follicles were labelled by CD32 and some CD16 antibodies. The immunolabelling of mantle zones was not present after washing the sections at low pH, which suggests that the molecules detected were passively absorbed on the cell surface (i.e. soluble FcyR). The immunolabelling of tonsil sections by various CDI 6 antibodies showed three patterns. The first (anti-Leu-I 1 b) revealed labelling of solitary macrophage-like cells. The second (BW20912 and 3G8) revealed, in addition, labelling of germinal centres. The third (CLBgranI and CLBgranI I ) revealed labelling of solitary cells and follicle mantles. This labelling on tissue sections was also seen in the analysis of follicular dendritic cells isolated from tonsil. The cells were faintly immunoreactive for 3G8, as well as for CD16 mAb CLBgranI, and both CD32 mAbs. In all tissues investigated there was immunoreactivity for FcyRs in varying intensity on endothelial cells of blood vessels.
We studied the distribution of Fc gamma RIII (CD16) in human lymphoid and non-lymphoid tissue by immunohistochemistry and two-colour immunofluorescence. In all tissues except stomach, skin, muscle and heart, infiltrating cells were stained. In tonsil and thymus, the CD16 antibody CLBgran 1 labelled some cells with high endothelial morphology in T-cell areas. Two-colour fluorescence combination of CD16 and antibody to Von Willebrand factor confirmed the endothelial nature of the CLB gran 1-positive cells. Fc gamma RIII expression was also demonstrated by antibody CLBgran11, which detects a product of the Fc gamma RIII-B gene of only the NA1 haplotype. A series of 95 endomyocardial biopsies (EMB) taken after heart transplantation was evaluated for Fc gamma RIII expression. In 18 cases Fc gamma RIII was unambiguously detected on endothelial cells by CD16 antibody CLBgran1. There was a significant correlation between capillary CD16 expression and transplant rejection. We conclude that Fc gamma R expression on endothelium represents endothelial activation found in immunopathological and inflammatory conditions.
Human monocytes express two types of IgG FcR, Fc gamma RI and Fc gamma RII. These can be assayed by using indicator E sensitized by human IgG (EA-human IgG) or mouse IgG1, (EA-mouse IgG1), respectively. On mouse macrophages, Fc gamma RI is sensitive to trypsin, whereas Fc gamma RII is trypsin resistant. We studied the effects of the proteolytic enzymes pronase and trypsin on human monocyte Fc gamma R. Neither enzyme caused a decrease in rosetting mediated by monocyte Fc gamma RI. Human Fc gamma RII is polymorphic, and monocytes interact either strongly or weakly with mouse IgG1. The interaction of low responder monocytes with mouse IgG1 was dramatically increased (to the level exhibited by high responder monocytes) by protease treatment. The effects of proteases on Fc gamma RII were investigated in more detail by using monocytes from which Fc gamma RI was selectively modulated by using immobilized immune complexes. Proteolysis of such modulated monocytes induced an increased interaction with EA-human IgG. Fc gamma RII appears to mediate this interaction. This conclusion is supported by the observation that after proteolysis, the Fc gamma RII-mediated binding of EA-mouse IgG1 becomes susceptible to inhibition by (monomeric) human IgG. To quantify the effect of proteolytic enzymes on Fc gamma RII, we performed binding studies with cell line K562, that expresses only Fc gamma RII. A significant increase in Ka of Fc gamma RII for dimeric human IgG complexes was observed when K562 cells were treated with protease. To elucidate the mechanism of this enhancement of Ka by proteolysis, we performed immunoprecipitation studies. Neither m.w., nor IEF pattern of Fc gamma RII were influenced by proteolysis. Moreover, the expression of Fc gamma RII was not affected by proteolysis as evidenced by immunofluorescence studies and Scatchard analysis, and neither were Fc gamma RI or Fc gamma RIII induced. We conclude that proteolysis increases the affinity of Fc gamma RII for human IgG, and speculate that such a proteolysis-induced change may also occur in vivo, e.g., at inflammatory sites.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.