Copyright © 2014 Agnieszka Klonowska-Szymczyk et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown aetiology. The results of experimental studies point to the involvement of innate immunity receptors—toll-like receptors (TLR)—in the pathogenesis of the disease. The aim of the study was to assess the expression of TLR3, 7, and 9 in the population of peripheral bloodmononuclear cells (PBMC) and in B lymphocytes (CD19+), T lymphocytes (CD4+ and CD8+) using flow cytometry. The study group included 35 patients with SLE and 15 healthy controls.Thepatient group presented a significantly higher percentage of TLR3- andTLR9-positive cells among all PBMCs and their subpopulations (CD3+, CD4+, CD8+, and CD19+ lymphocytes) as well as TLR7 in CD19+ B-lymphocytes, compared to the control group. There was no correlation between the expression of all studied TLRs and the disease activity according to the SLAM scale, and the degree of organ damage according to the SLICC/ACR Damage Index. However, a correlation was observed between the percentage of various TLR-positive cells and some clinical (joint lesions) and laboratory (lymphopenia, hypogammaglobulinemia, anaemia, and higher ESR) features and menopause in women.The results of the study suggest that TLR3, 7, and 9 play a role in the pathogenesis of SLE and have an impact on organ involvement in SLE. 1.

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