Common variable immunodeficiency (CVID) is the most common clinical primary antibody deficiency, characterized by increased susceptibility to recurrent bacterial infections. Since Toll-like receptors (TLRs) play an important role in the maturation and differentiation of B-cells, TLRs' defect can be involved in the pathogenesis of CVID. Therefore, we evaluated the expression of TLR2 and TLR4 and their signaling pathway; also their association with autoimmunity, B-cell subtypes and response to pneumovax-23 were assessed in CVID patients. Sixteen CVID patients were enrolled in the study. Flow cytometry was used for assessing the protein expression of TLR2 and TLR4, and real-time PCR was used for gene expression of myeloid differentiation primary response 88 (MyD88) and toll interacting protein (Tollip). We found a higher protein expression of TLR2 in CVID patients which was associated with lower number of end stage B-cells and hyporesponse to pneumovax-23 vaccination. We showed a lower mRNA expression of MyD88 and an almost equal Tollip mRNA expression in CVID patients compared with controls. There was a profound association between MyD88 gene expression and autoimmunity in CVID patients. According to the presence of the lower number of end stage B-cells and poor vaccine response in CVID patients and their correlation with the higher expression of TLR2, we hypothesized that there is a functional defect in this receptor and/or its downstream in the peripheral blood mononuclear cells (PBMCs) of CVID patients.
Keywords: Common variable immunodeficiency (CVID); Myeloid differentiation primary response 88 (MyD88); Toll interacting protein (Tollip); Toll-like receptor 2 (TLR2); Toll-like receptor 4 (TLR4).