Also, significantly more ITP patients harboured ORF SNPs (34·5%) compared to healthy controls (18·0%; P = 0·009). Further investigations demonstrated that FCGR2C harbouring an ORF encodes a surface expressed FcγRIIc on natural killer (NK) cells (Fig. 5). Furthermore, NK cells

with FcγRIIc can mediate antibody-dependent cellular cytotoxicity (ADCC) to antibody-coated targets, demonstrating that FcγRIIc acts as an activating IgG receptor. IVIG-induced anaphylaxis in a patient with CVID has been shown to be probably related to variation in FCGR genes (Kuijpers, unpublished data). A Caucasian female was diagnosed with CVID. She had recurrent infections and chronic Giardia lamblia-related diarrhoea. After the start of IVIG, the patient complained of abdominal pain, a generalized rash, tachypnoea and tachycardia with a fall in blood pressure, followed by chills and fever. IVIG Tanespimycin molecular weight infusion was stopped and anti-histamines (clemastin, 2 mg), Selleckchem Dorsomorphin steroids (DAF, 25 mg) and NaCl 0·9% (500 ml) were administered intravenously. Blood cultures remained sterile, concentrations of serum tryptase and complement activation products

were not increased; however, elevated elastase was detected. IgG–anti-IgA complexes are not always clinically relevant and are no longer tested for routinely prior to infusion. In this case, due to the anaphylaxis, preinfusion serum samples were analysed and showed the presence of anti-IgA antibodies of the IgG1 subclass. Investigation of FCGR2 revealed a novel splice variant in exon 6 of FcγRIIa that is characterized by normal mRNA and protein expression, and represents a potential gain-of-function variant through elongation of the cytoplasmic tail. The expression of this splice variant has been found in eight individuals, including one patient with CVID, three with vasculitis of whom one developed insulin-dependent diabetes type 1 and in one healthy control. FcγRIIa-mediated hyper-reactivity may be proposed as a mechanism to explain severe anaphylactic reaction to IVIG. More CVID patient serum samples are required to fully characterize the clinical response. Thus, FCGR2C represents a gene with variable expression that is highly relevant for immunity, probably contributing

to susceptibility and severity of infections and autoimmune disease. A balance between inhibitory (FcγRIIb) and activating FcγRs (FcγRIIa, FcγRIIcorf, FcγRIIIa, FcγRIIIb) is important for immune Resveratrol reactivity. High-dose IVIG treatment is thought to exert an immunomodulatory effect by numerous mechanisms, including engagement of the inhibitory FcγRIIb receptor and/or by saturation of the neonatal Fc receptor, FcRn. FcRn is a human leucocyte antigen (HLA) class I-related receptor that transports IgG antibodies within and across a diverse array of different cell types. Through this transport, FcRn serves multiple roles throughout adult life that extend well beyond its previously defined function of transcytosing IgG molecules from mother to offspring.