T cell functions of psoriatic arthritis patients are regulated differently by TNF, IL-17A and IL-6 receptor blockades in vitro.

Objectives: The impact of biologics used in PsA management on T cells is unknown. This study evaluated the effect of tumour necrosis factor-alpha (TNFα), interleukin-17A (IL-17A), and IL-6 receptor (IL-6R) blockers on T cell function in PsA patients and healthy controls peripheral blood mononuclear cells (PBMCs).

Methods: A total of 111 PsA patients and 32 healthy controls were recruited. PBMCs were co-cultured in presence of the biologics. T cell activation and proliferation were analysed by flow cytometry and cytokines in supernatants were measured by ELISA. The effect of biologics on lymphocyte proliferation was determined in response to phytohemagglutinin (PHA).

Results: Activated CD4+CD25+ T cells were significantly reduced by adalimumab (ADA) in PsA patients as compared to medium, ixekizumab (IXE), and tocilizumab (TCZ), while in healthy controls, ADA reduced the activated CD4+CD25+ T cells non-significantly. Elevated TNFα and IL-1β levels were produced in supernatants of PsA patients as compared to healthy controls. TNFα, IL-17A, IL-1β, and MMP-3 levels were reduced by ADA compared to medium (p<0.0001, p<0.0004, p<0.04, p<0.04, respectively). IXE reduced IL-17A (p<0.0001) but not the other cytokines. ADA had higher susceptibility to inhibit PHA-induced proliferation in both PsA patients and healthy controls (p<0.03) as compared to IXE and TCZ.

Conclusions: Both TNF and IL-17A blockers are suitable for PsA treatment, but exhibit different activity on T cells. Moreover, the study reveals part of the mechanism exerted by ADA and provides a possible explanation for TCZ inefficacy in PsA.