title: Expression profile of FcgammaRIIb on leukocytes and its dysregulation in systemic lupus erythematosus.
abstract: FcgammaRIIb (CD32B, Online Mendelian Inheritance in Man 604590), an IgG FcR with a tyrosine-based inhibitory motif, plays a critical role in the balance of tolerance and autoimmunity in murine models. However, the high degree of homology between FcgammaRIIb and FcgammaRIIa in humans and the lack of specific Abs to differentiate them have hampered study of the normal expression profile of FcgammaRIIb and its potential dysregulation in autoimmune diseases such as systemic lupus erythematosus (SLE). Using our newly developed anti-FcgammaRIIb mAb 4F5 which does not react with FcgammaRIIa, we found that FcgammaRIIb is expressed on the cell surface of circulating B lymphocytes, monocytes, neutrophils, myeloid dendritic cells (DCs), and at very low levels on plasmacytoid DCs from some donors. Normal donors with the less frequent 2B.4 promoter haplotype have higher FcgammaRIIb expression on monocytes, neutrophils, and myeloid DCs similar to that reported for B lymphocytes, indicating that FcgammaRIIb expression on both myeloid and lymphoid cells is regulated by the naturally occurring regulatory single nucleotide polymorphisms in the FCGR2B promoter. FcgammaRIIb expression in normal controls is up-regulated on memory B lymphocytes compared with naive B lymphocytes. In contrast, in active SLE, FcgammaRIIb is significantly down-regulated on both memory and plasma B lymphocytes compared with naive and memory/plasma B lymphocytes from normals. Similar down-regulation of FcgammaRIIb on myeloid-lineage cells in SLE was not seen. Our studies demonstrate the constitutive regulation of FcgammaRIIb by natural gene polymorphisms and the acquired dysregulation in SLE autoimmunity, which may identify opportunities for using this receptor as a therapeutic target.
authors.affiliation: Division of Clinical Immunology and Rheumatology, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Kaihong
authors.initials: K
authors.lastname: Su
authors.forename: Hengxuan
authors.initials: H
authors.lastname: Yang
authors.forename: Xinrui
authors.initials: X
authors.lastname: Li
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Li
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Gibson
authors.forename: John M
authors.initials: JM
authors.lastname: Cafardi
authors.forename: Tong
authors.initials: T
authors.lastname: Zhou
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Edberg
authors.forename: Robert P
authors.initials: RP
authors.lastname: Kimberly
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology; D015551:Autoimmunity / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D007962:Leukocytes / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D008180:Lupus Erythematosus, Systemic / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D008297:Male; D051379:Mice; D020641:Polymorphism, Single Nucleotide / Q000276:immunology; D011401:Promoter Regions, Genetic; D017452:Receptors, IgG / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology
chemical_list: D015703:Antigens, CD; C499173:FCGR2B protein, human; C080568:Fc gamma receptor IIA; D017452:Receptors, IgG