Furthermore, patients with autoimmune diseases have lower percentage of Tregs compared to those without autoimmunity. In agreement with these results, previous studies showed that the frequency of Tregs is decreased in CVID patients and its correlations with chronic inflammation, splenomegaly and autoimmune manifestation have also been described [17-21]. Tregs were initially introduced by Shimon Sakaguchi and his colleagues  as a unique subset of CD4+ T cells that constitutively express high levels of surface IL-2 receptor α chain, CD25 and transcription factor www.selleckchem.com/products/chir-99021-ct99021-hcl.html FOXP3 and have potent immunoregulatory properties [9, 25]. This population of T lymphocytes also express
other markers including CTLA-4, GITR, LAG-3 (CD223), galectin-1 and low levels of CD127 (IL-7 receptor α) . Controlling the homoeostasis of Tregs can be exerted in different aspects like their thymic development
and differentiation, half-life in circulation and their tissue redistribution . Therefore, it is tempting to believe that changes in each of these checkpoints might reflect Tregs’ populations in peripheral blood of CVID patients particularly those with autoimmune diseases. One possible explanation is the homing of Tregs from blood into the site of inflammation. Defect in thymic development should also be considered because defect in thymopoiesis has been reported in some studies in CVID patients [27, 28]. Common variable immunodeficiency shares many clinical phenotypes Bortezomib in vitro with selective IgA deficiency (SIgAD) associating with severe complication, and progression from SIgAD to CVID has also been reported in several cases [29, 30]. In our previous report, it was presented for the first time that the frequency of Tregs is lower in patients with SIgAD, especially those with autoimmune diseases . Therefore, it could be hypothesized that reduced number of Tregs’ cells may play a similar role in the pathogenesis of both diseases. Carter et al.  conducted a study to
compare the levels of regulatory T cells and the activation markers of T cell subsets in 23 CVID patients and to clarify their possible interaction leading to acetylcholine autoimmunity. Similar to finding of this study, they showed that patients especially those with autoimmune manifestation had reduced levels of Tregs compared with control group. Moreover, they found that elevated T cell expression of granzyme B and HLA-DR had another indicators predisposing CVID patients to autoimmunity. We further investigate the key molecules involved in Tregs’ functions including FOXP3, CTLA-4 and GITR markers. In complete agreement with other published data, CVID patients had diminished expression of FOXP3 protein compared to controls as well as those with autoimmunity compared to non-autoimmune ones [18, 20]. Additionally, a positive correlation was seen between the frequency of Tregs and FOXP3 expression.