Restoration of peripheral blood natural killer and B cell levels in patients affected by rheumatoid and psoriatic arthritis during etanercept treatment

Abstract

Etanercept (ETN) is an anti-tumour necrosis factor (TNF)-α agent used in rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Few studies focused on the effects of anti-TNF-α on peripheral blood cells. We aimed to evaluate peripheral blood cells in RA and PsA patients during ETN treatment and to explore their relationships with disease activity. RA (n = 82) and PsA (n = 32) patients who started ETN were included into the study and evaluated prospectively before the beginning of ETN therapy and after 14, 22, 54 and 102 weeks. Patients were studied in terms of disease activity score on 28 joints (DAS28), clinical response and laboratory findings. Natural killer (NK) cells, B cells and T cells were characterized by immunophenotyping. Both the RA and the PsA patients showed reduced NK and B cell count before ETN treatment compared with controls. A negative correlation was demonstrated between DAS28 and B cell count in RA patients at baseline. Sustained significant increase of NK and B cells up to normal levels was observed in RA and PsA patients along ETN treatment. Increase of NK cell count was associated with a good-moderate clinical response to ETN in both RA and PsA patients. During ETN treatment peripheral blood NK and B cells levels were restored in RA and PsA patients. Correlations between NK and B cells with disease activity were observed, suggesting that those effects could be mediated by ETN treatment.

Keywords: B cell; arthritis; autoimmunity; natural killer cells.

Fig. 1

Circulating CD16⁺CD56⁺ natural killer (NK) and CD19⁺ B cells in a healthy control (HC) and a rheumatoid arthritis (RA) patient. Representative examples of dot-plots from one HC (a,b) and one RA patient (c,d). (a) The gating strategy with the lymphocyte population identified by CD45 (indicated with P1). CD45⁺CD56⁺ cells identified NK cells and CD45⁺CD19⁺ cells showed B cells in a HC (b). (c) CD45⁺CD56⁺ NK cells and CD45⁺CD19⁺ B cells are shown in a representative RA patient before etanercept treatment. (d) CD45⁺CD56⁺ and CD45⁺CD19⁺ cells of the same RA patient are shown after 102 weeks of etanercept treatment.

Fig. 2

Circulating natural killer (NK) cells during etanercept treatment. Circulating NK cell numbers in treated rheumatoid arthritis (RA) (n = 82) (a), treated psoriatic arthritis (PsA) patients (n = 32) (b), disease-modifying anti-rheumatic drugs (DMARDs)-free RA (n = 26) (c) and DMARDs-free PsA (n = 19) (d) patients before and after etanercept at different time-points. Data registered in healthy controls (n = 45) are reported in each panel. Data are shown as box-plots; each box represents the 25th–75th percentiles; lines inside the box represent the median. The whiskers represent the 95% confidence interval (CI). Statistical analyses in patients and controls were performed using the Mann–Whitney U-test, while Wilcoxon's signed-rank test was used to compare cells pre- and post-treatment. *P < 0·05; **P < 0·01; ***P < 0·001.

Fig. 3

Disease activity score on 28 joints (DAS28), circulating natural killer (NK) and B cell numbers in patients treated with etanercept. DAS28 levels, circulating NK and B cell number in rheumatoid arthritis (a) and psoriatic arthritis patients (b) before and after 14, 22, 54 and 102 weeks of treatment with etanercept. Each value represents mean ± standard error.

Fig. 4

Circulating natural killer (NK) cells in rheumatoid arthritis (RA) and psoriatic arthritis (PsA) patients according to the clinical response. NK cell numbers in RA (a) and PsA (b) patients classified as responders (Resp) and no-responders (No-resp) after 54 and 102 weeks of treatment with etanercept. Data are shown as box-plots, where each box represents the 25th–75th percentiles; lines inside the box represent the median. The whiskers represent the 95% confidence interval (CI). Statistical analyses were performed using Wilcoxon's signed-rank test. *P < 0·05; **P< 0·01.

Fig. 5

Circulating B cell numbers during etanercept treatment. Circulating B cell numbers in treated rheumatoid arthritis (RA) (n = 82) (a), treated psoriatic arthritis (PsA) (n = 32) (b), disease-modifying anti-rheumatic drugs (DMARDs)-free RA (n = 26) (c) and DMARDs-free PsA patients (n = 19) (d) during etanercept treatment. Data registered in healthy controls (n = 45) are reported in each panel. Data are shown as box-plots, where each box represents the 25th–75th percentiles; lines inside the box represent the median. Whiskers represent the 95% confidence interval (CI). Statistical analyses in patients and controls were performed using the Mann–Whitney U-test, while Wilcoxon's signed-rank test was used to compare cell population pre- and post-treatment. *P < 0·05; **P < 0·01; ***P < 0·001.

Fig. 6

Circulating B cells and clinical outcome in rheumatoid arthritis (RA) and psoriatic arthritis (PsA) patients. (a) Negative correlation between disease activity score on 28 joints (DAS28) levels and B cell numbers in RA patients (n = 82) before etanercept treatment. The correlation was assessed by Spearman's rank order correlation test. (b) B cell numbers in responders and no-responders PsA patients after 14 weeks of treatment with etanercept. Data are shown as box-plots, where each box represents the 25th–75th percentiles; lines inside the box represent the median. Whiskers represent the 95% confidence interval (CI). Statistical analyses were performed using Wilcoxon's signed-rank test. *P < 0·05.