Background and Objective Recently, we showed increased T cell activation in lymph node biopsies of early rheumatoid arthritis (RA) patients. We hypothesise that different lymph node T-cell subsets are involved in the regulation of immune responses during the earliest phases of RA.

Materials and Methods We included 11individuals with arthralgia without any evidence of arthritis who were positive for IgM rheumatoid factor (IgM-RF) and/or anti-citrullinated protein antibodies (ACPA; RA risk group), 18 DMARD naïve early arthritis patients (ACR/EULAR 2010 criteria: 3 undifferentiated arthritis and 15 RA; disease duration less than 1 year) and 10 seronegative healthy controls. All study subjects underwent ultrasound-guided inguinal lymph node (LN) biopsy sampling. Gene expression profiling of whole LN biopsies (10 controls and 8 ACPA positive early arthritis patients) was performed using the Illumina array platform. Gene Set Enrichment Analyses (GSEA) was used to search for significant enrichment of immunological gene sets representing certain classes of cell subsets. In all other study subjects T-helper (Th)1, cytotoxic T-cell (Tc)1, Th2, Tc2, Th17, Tc17 and regulatory T-cells (Treg) were analysed by multi-colour flow cytometry.

Results First we investigated whether gene expression profiles of lymph node biopsies from ACPA positive early arthritis patients (n = 8) are different from seronegative controls (n = 10). A false discovery rate of <25% revealed 131 genes with significantly increased expression in patients compared with controls. In line with our previous work, several of these genes are involved in B cell biology. GSEA analyses revealed 347 immunological signature gene sets to be significantly enriched in patients compared with controls. T-cell related gene sets indicated increased expression of both effector and regulatory T-cell genes in ACPA positive arthritis. In line with these findings, flow cytometry analyses revealed an increase of IL-17A producing CD4 T-cells (Th17; p = 0.05), IL-10 producing CD4 T-cells (p = 0.001) and foxp3 positive CD4 T-cells (p = 0.008) in an independent group of early arthritis patients compared to RA risk individuals. Interestingly, in the early arthritis patients a significant correlation was observed between ACPA titers and IL-10 producing (r = 0.71; p = 0.03) and IL-17A producing CD4 T-cells (r = 0.74; p = 0.015).

Conclusions These data clearly show that pro-inflammatory as well as regulatory cytokines and T-cell subsets are increased in peripheral lymphoid tissue during the earliest phases of arthritis, suggesting an early change in the immunoregulatory balance.