Furthermore, IgG3 binds with high affinity to Fc receptors on macrophages, and thus may be important in antibody-mediated find more phagocytosis [2]. These factors may explain why patients with isolated IgG3 deficiency present with recurrent upper respiratory tract infections. However, the propensity for infections in these patients may not be attributed solely to IgG3 deficiency. There have been reports of patients with complete absence of IgG3 due to gene deletion in the heavy chain constant

regions, but these patients have had no infectious complications [3]. Therefore, other immune dysfunctions might exist in those patients with isolated IgG3 deficiency and recurrent infections. A more detailed analysis of immune function in IgG3-deficient patients is needed. The majority of reported studies for IgG subclass deficiency have been in children [4–6], and very few studies have reported detailed clinical and immunological features of adult patients with IgG3 deficiency [7–8]. In some of these reports, IgG3 subclass deficiency was associated with either IgA deficiency or another subclass deficiency, and therefore may not be considered selective IgG3 deficiency. R788 cell line Moreover, none of these studies reported immunological data. Finally, there is a lack of information about the use of intravenous

immunoglobulin for treatment of IgG3 subclass deficiency. In this study, we present detailed information regarding immune functions of patients with recurrent infections and isolated IgG3 deficiency, and their response to intravenous Ig therapy (IVIG). We reviewed the charts of patients with recurrent infections referred to one of us (S. G.) at Immunology Clinic, University of California, Irvine (UCI) from 1998 to 2007. We identified 17 adult patients with a diagnosis of selective IgG3 deficiency. The diagnosis was made according to published guidelines [9]. Patients

were 16 years of age or older at the time of diagnosis, suffered from recurrent Cell press infections, had an IgG3 level that was greater than 2 standard deviations below the mean on at least two separate occasions and had normal levels of IgA, IgM, IgG, IgG1, IgG2 and IgG4. The charts of these 17 patients were reviewed for immunological data, the type and frequency of infections and response to IVIG treatment. This study was approved by the UCI Institutional Review Board, and the patients signed informed consent. Fluorescein isothiocyanate (FITC)- and phycoerythrin (PE)-conjugated monoclonal antibodies to CD3, CD4, CD8, CD19, CD16, CD56, CD14, Toll-like receptor-4 (TLR-4) and isotype controls were obtained from Becton Dickinson (San Jose, CA, USA). Tritiated thymidine [3H] for lymphocyte transformation assays was obtained from New England Nuclear (Boston, MA, USA).