Selective recruitment of CXCR3⁺ and CCR5⁺ CD4 ⁺ T cells into synovial tissue in patients with rheumatoid arthritis

The inflamed synovial tissue (ST) of rheumatoid arthritis (RA) is characterized by the selective accumulation of interferon γ-producing Th1-type CD4⁺ T cells. In this study, we investigated whether the predominance of Th1-type CD4⁺ cells in the ST lesion is mediated by their selective recruitment through Th1 cell-associated chemokine receptors CXCR3 and CCR5. The lymphocyte aggregates in the ST of RA contained a large number of CD4⁺ T cells, which mostly expressed both CXCR3 and CCR5, but not CCR4. In contrast, the frequencies of CD4⁺ and CD8 ⁺ T cells expressing CXCR3 and CCR5 in the blood were significantly decreased in RA patients, compared with healthy controls (HC), although there was no difference in the frequencies of CCR4-expressing CD4⁺ and CD8⁺ T cells between RA and HC. CXCR3, CCR5, and CCR4 expression in blood CD4⁺ T cells and CXCR3 expression in CD8⁺ T cells were increased after interleukin-15 (IL-15) stimulation. Therefore, the distribution of Th1-type CD4⁺ T cells into the ST from the blood in RA may be associated with the local expression of chemokines, both CXCR3 and CCR5 ligands, and IL-15 may play a role in enhancing these chemokine receptors on CD4⁺ T cell infiltrates. Copyright