Differential expression of TLR2 and TLR4 in α4β7-positive leukocytes of patients with axial spondyloarthritis

Objectives. Expression of alpha 4 beta 7 integrin can identify gut-homing immune cells. This study aimed to determine the expression of Toll-like receptor 2 (TLR2) and TLR4 in alpha 4 beta 7-positive leukocytes of patients with axial SpA (axSpA). Methods. We analysed the frequencies of alpha 4 beta 7-positive T cells, T gamma delta cells and monocytes in 14 patients with axSpA and 14 healthy controls, together with the expression of TLR2 and TLR4 by flow cytometry. Also, the concentration of faecal calprotectin was measured in all patients and controls. Results. We found significantly higher percentages of alpha 4 beta 7-positive T (P = 0.026) and T gamma delta cells (P = 0.0118) in the patients with axSpA than in controls; these cells showed differential expression of TLR2 and TLR4 when compared with alpha 4 beta 7-negative cells. Such differences were not correlated with disease activity or faecal calprotectin concentration. Conclusion. There is an increase in circulating alpha 4 beta 7-positive T and T gamma delta cells in patients with axSpA. These cells differentially express TLR2 and TLR4.