Anti-FCGR3 monoclonal antibody, clone FCR4G8 [FITC]

Itraconazole (ICZ) is commonly used for the treatment of fungal infections, particularly in immunocompromised patients. In addition, ICZ has been recently found to have antiangiogenic effects and is currently being tested as a new chemotherapeutic agent in several cancer clinical trials. We have previously shown that ICZ impaired complex N-linked glycosylation processing, leading to the accumulation of high-mannose glycoproteins on the surface of macrophages (MOs). This investigation was directed at determining the effects of ICZ on phagocytosis as a major function of MOs. We found a significant decrease in the phagocytosis of opsonized bacterial particles in ICZ-treated murine MOs in comparison with nontreated MOs. Furthermore, the impairment of phagocytosis was associated with a decrease in cell surface expression of Fc receptors (FcRs) as well as alteration of their glycosylation pattern. Concomitantly, a reduction in all three isoforms of the FcR family (i.e., Fcgr1, Fcgr2, and Fcgr3) mRNA levels was observed after incubation with ICZ. The effect of ICZ on phagocytosis and FcR expression was reversed by addition of low-density lipoprotein. These studies indicate that ICZ treatment certainly has a dramatic effect on macrophage function, which could result in a potential impairment of the immune system';s ability to respond to pathogens and may lead to an elevated incidence of infections.

This study was designed to investigate whether MafB influences the phagocytic activity of macrophages by modulating the expression of the Fc receptors for IgG (Fc gamma Rs), Fcgr2b and Fcgr3. In macrophages, Fc gamma Rs are critical for the phagocytosis of opsonized pathogens. Of these receptors, Fcgr3 has been shown to play an important role in host defense. As a model to evaluate the mechanism by which MafB influences phagocytosis, we utilized a macrophage cell-line that constitutively expresses a MafB-specific short hairpin (sh)RNA (RAW264.7-MafB-shRNA). Specifically, the levels of Fc receptor mediated-phagocytosis and the levels of Fc gamma Rs surface expression were evaluated by flow cytometry analysis, while quantitative real-time PCR analysis was utilized to examine the mRNA expression levels of Fc gamma Rs. Compared to the control cell population, RAW264.7-MafB-shRNA cells exhibited significant reductions in Fcgr3 expression and Fc receptor-mediated phagocytosis, but no difference in Fcgr2b expression. Likewise, there was markedly decreased surface expression of Fcgr3 antigen, but not Fcgr2b antigen, in RAW264.7-MafB-shRNA, compared to the control cells. Meanwhile, the observed reduction in the phagocytic activity of the MafB-shRNA-expressing cells was attenuated by ectopic expression of Fcgr3. Together, the results presented here indicate that MafB influences the phagocytic activity of macrophages by promoting Fcgr3, but not Fcgr2b, expression. (C) 2016 Elsevier Inc. All rights reserved.