IL-17 and IFN-γ producing NK and γδ-T cells are preferentially expanded in synovial fluid of patients with reactive arthritis and undifferentiated spondyloarthritis

The IL-17/1L-23 axis is important in the pathogenesis of spondyloarthropathy. Innate cells produce IL-17 in addition to Th17 cells. We studied the frequencies of natural killer (NK) (total, CD56bright, CD56dim, perforin + and granzyme +), NK-T, γδ-T, and IFN-γ +, IL-17 + NK and γδ-T cells in peripheral blood (PB) and synovial fluid (SF) of ReA/uSpA patients. PB from 45 patients and paired SF from 39 patients were studied, together with PB from 18 healthy controls (HC). The frequency of γδ-T cells was decreased (p < 0.05) while IL-17 producing NK and γδ-T cells were increased (p < 0.05) in PB of patients as compared to HC. In SF, CD56bright NK cells were increased (p < 0.001) but had reduced expression of perforin and granzyme (p < 0.0001) as compared to PB. Frequency of IL-17 +, IFN-γ + NK and γδ-T cells was higher in SF as compared to PB (p < 0.05). We suggest that innate cells by producing pro-inflammatory cytokines may contribute to pathogenesis.