PD-1+CXCR5-CD4+T Cells Are Correlated with the Severity of Systemic Lupus Erythematosus

OBJECTIVES:

PD-1+CXCR5-CD4+T peripheral helper (Tph) cells, a recently identified T cell subset, are proven to promote B cell responses and antibody production in rheumatoid arthritis, but their role in the pathogenesis of SLE is unknown. We explored the role of Tph in lupus disease development.

METHODS:

This cohort study included 68 patients with SLE and 41 age- and sex-matched healthy individuals. The frequency of PD-1+CXCR5-CD4+T cells was analysed in peripheral blood by flow cytometry. Inducible T-cell costimulator, CD38, MHC-II, IL-21, CXCR3 and CCR6 expression were measured in Tph cells. Comparisons between the two groups were performed, and correlations between Tph cells and other parameters were investigated.

RESULTS:

We revealed a markedly expanded population of Tph cells (8.31 ± 5.45 vs 2.86 ± 1.31%, P < 0.0001) in the circulation of patients with SLE (n = 68), compared with healthy controls (n = 41). Tph cells were much higher in the active group than in the inactive group (14.21 ± 5.21 vs 5.49 ± 2.52%, P < 0.0001). Tph cells were significantly associated with SLEDAI score (r = 0.802), ESR (r = 0.415), IgG (r = 0.434), C3 (r = -0.543), C4 (r = -0.518) and IL-21 level (r = 0.628), and ANA titre (r = 0.272). Furthermore, Tph cells were much higher in lupus patients with arthritis, nephritis, rash, alopecia, pleuritis, pericarditis and haematological involvement. Tph cells were associated with CD138+/CD19+ plasma cells (r = 0.518). Furthermore, MHC-II, inducible T-cell costimulator, CD38, and IL-21 expression were all higher in Tph cells from SLE patients compared with healthy controls. CXCR3+CCR6-Tph (Tph1) cells were expanded in the SLE patients.

CONCLUSION:

Our data show that relative number of Tph cells is correlated with disease measures in patients with SLE, suggesting an important role in lupus disease development.