CCR6⁺ Th cell populations distinguish ACPA positive from ACPA negative rheumatoid arthritis

Patients with rheumatoid arthritis (RA) can be separated into two major subpopulations based on the absence or presence of serum anti-citrullinated protein antibodies (ACPAs). The more severe disease course in ACPA⁺ RA and differences in treatment outcome between these subpopulations suggest that ACPA⁺ and ACPA⁻ RA are different disease subsets. The identification of T-helper (Th) cells specifically recognizing citrullinated peptides, combined with the strong association between HLA-DRB1 and ACPA positivity, point toward a pathogenic role of Th cells in ACPA⁺ RA. In this context we recently identified a potential pathogenic role for CCR6⁺ Th cells in RA. Therefore, we examined whether Th cell population distributions differ by ACPA status.

We performed a nested matched case–control study including 27 ACPA⁺ and 27 ACPA⁻ treatment-naive early RA patients matched for disease activity score in 44 joints, presence of rheumatoid factor, sex, age, duration of complaints and presence of erosions. CD4⁺CD45RO⁺ (memory) Th cell distribution profiles from these patients were generated based on differential chemokine receptor expression and related with disease duration.

ACPA status was not related to differences in total CD4⁺ T cell or memory Th cell proportions. However, ACPA⁺ patients had significantly higher proportions of Th cells expressing the chemokine receptors CCR6 and CXCR3. Similar proportions of CCR4⁺ and CCR10⁺ Th cells were found. Within the CCR6⁺ cell population, four Th subpopulations were distinguished based on differential chemokine receptor expression: Th17 (CCR4⁺CCR10⁻), Th17.1 (CXCR3⁺), Th22 (CCR4⁺CCR10⁺) and CCR4/CXCR3 double-positive (DP) cells. In particular, higher proportions of Th22 (p = 0.02), Th17.1 (p = 0.03) and CCR4/CXCR3 DP (p = 0.01) cells were present in ACPA⁺ patients. In contrast, ACPA status was not associated with differences in Th1 (CCR6⁻CXCR3⁺; p = 0.90), Th2 (CCR6⁻CCR4⁺; p = 0.27) and T-regulatory (CD25^hiFOXP3⁺; p = 0.06) cell proportions. Interestingly, CCR6⁺ Th cells were inversely correlated with disease duration in ACPA⁻ patients (R² = −0.35; p < 0.01) but not in ACPA⁺ (R² < 0.01; p = 0.94) patients.

These findings demonstrate that increased peripheral blood CCR6⁺ Th cells proportions distinguish ACPA⁺ RA from ACPA⁻ RA. This suggests that CCR6⁺ Th cells are involved in the differences in disease severity and treatment outcome between ACPA⁺ and ACPA⁻ RA.