We have previously reported high immunoglobulin expression in human omental adipose tissue. The aim of this work was to investigate plasma cell density and Fe receptor (FcR) expression in human adipose tissue depots and in vitro effects of immunoglobulins oil adipocyte function. Plasma cell density was higher in the visceral compared to the subcutaneous depot (10.0 +/- 1.56% and 5.2 +/- 0.98%. respectively, n = 20, p < 0.05). Microarray analysis revealed expression of four FcR genes in adipose tissue; FCGR2A, FCGR2B, FCER1G, and FCGRT. FCGR2A was highly expressed in adipocytes in both depots and this was verified by immunohistochemistry. Expression of IL-1 beta and IL-6 was markedly reduced in adipocytes after incubation with the Fc moiety of iinmunoglobulin G (Fc) (p < 0.01). Furthermore, Fc stimulated adipocyte lipogenesis as potently as insulin (p < 0.05), but did not influence lipolysis. In conclusion, immunoglobulins produced by plasma cells in human adipose tissue could influence adipocyte metabolism and cytokine production. (c) 2006 Elsevier Inc. All rights reserved.