CD8+ T cells are plentiful in rheumatoid arthritis (RA) and have a important role in it’s pathogenesis. Many subsets have been identified in CD8+ T cells, however, the relationship between CD8+ T subpopulations and disease activity of RA is poorly defined. Here we detected different CD8+ T cell subsets in peripheral blood and examined their relationships with clinical features and serological parameters in RA.

Naive CD8+ T cells were significantly and negatively correlated with RA disease activity indicator DAS28-ESR(r2 = 0.1027, p = 0.0468), erythrocyte sedimentation rate (ESR)(r2 = 0.1891, p = 0.0057), clinical disease activity index(CDAI)(r2 = 0.1474, p = 0.0158), simplified disease activity index(SDAI)(r2 = 0.1465, p = 0.0255), and duration(r2 = 0.1247, p = 0.0274). And the percent of naive CD8+ T cells were obviously decreased in RA with high disease activity when compared with RA in low disease activity(p < 0.01). In addition, Our results indicated significant positive correlations between CD8+ CD28- T cells and DAS28-ESR(r2 = 0.1881, p = 0.0058), ESR(r2 = 0.2279, p = 0.0021), c reaction protein (CRP)(r2 = 0.2203, p = 0.0051), CDAI (r2 = 0.1778, p = 0.0075), SDAI (r2 = 0.2618, p = 0.0020), rheumatoid factor(RF)(r2 = 0.1823, p = 0.0067), age(r2 = 0.1968, p = 0.0047), as well as similar positive correlations between CD8+ CD27- T cells and DAS28-ESR(r2 = 0.1661, p = 0.01), ESR(r2 = 0.1586, p = 0.012), CRP(r2 = 0.1778, p = 0.013), CDAI (r2 = 0.1622, p = 0.0110), SDAI(r2 = 0.2316, p = 0.0040), RF(r2 = 0.2097, p = 0.0034), age(r2 = 0.1932, p = 0.0051). Furthermore, interesting results showed observable positive correlations between activated CD8+ T cells and total cholesterol(TC)(r2 = 0.2757, p = 0.0007), triglyceride(TG)(r2 = 0.2886, p = 0.0005), low density lipoprotein(LDL-C)(r2 = 0.09643, p = 0.0264) and Krebs yon denlungen-6(KL-6)(r2 = 0.4171, p = 0.0002). And TCRγδ + CD8+ T cells were also found positively related with total cholesterol(TC)(r2 = 0.5015, p < 0.0001), triglyceride(TG)(r2 = 0.2031, p = 0.0045), and KL-6(r2 = 0.2122, p = 0.0136).

Our results suggest that naive CD8+ T cells, CD8+ CD28- T cells, and CD8+ CD27- T cells are obviously correlated with inflammation and disease activity of RA. While activated CD8+ T cells and TCRγδ + CD8+ T cells may involve in lipid metabolism and lung fibrosis of RA. These CD8+ T cell subsets may be new biomarkers and targets for RA disease evaluation, therapeutic target-selecting, curative effects and prognoses assessment.