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

Summary 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 ( DAS 28), clinical response and laboratory findings. N atural 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 DAS 28 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.