Toll-like receptors pathway in common variable immune deficiency (CVID) and X-linked agammaglobulinemia (XLA)

Common variable immunodeficiency (CVID) and X-linked agammaglobulinemia (XLA) are two major humoral immunodeficiencies, causing a high rate of early age mortality in children. In order to identifiy the possible factors involved in the pathogenesis of CVID and XLA, recent studies have focused on Toll-like receptors (TLRs) and demonstrate the defects in different TLR pathways in immune cells of CVID and XLA patients. Herein, we measured TLR-4 and TLR-9 RNA levels and consequently TNF-α and IFN-α production in peripheral blood mononuclear cells (PBMCs) of patients with CVID and XLA. Contrary to healthy individuals, TLR-9 expression was not significantly increased after ligand stimulation, whereas ligand-induced TLR-4 expression was not significantly different from that in healthy control PBMCs. Lipopolysaccharide (LPS)-stimulated TNF-α production was significantly reduced in patients compared to controls, whereas IFN-α production was increased in all groups after CpG stimulation without any significant inter-group difference. Our data suggest that defects in TLR-9 activated pathways may be a result of the decreased TLR-9 expression, although TLR-9 is not the only modulator of IFN-α production in these patients. On the other hand, impaired signaling in TLR-4 activated pathways which results in significant reduction in TNF-α production are not related to a defect in TLR-4 expression.