Background Previous studies indicated a potential role for mucosal-associated invariant T (MAIT) cells in the pathogenesis of ankylosing spondylitis (AS).^1,2 Active peripheral arthritis and extra-articular manifestations may influence the presence of circulating MAIT cells in AS.

Objectives To investigate circulating MAIT cells in a homogenous group of axial spondyloarthritis (SpA) patients with only axial involvement in comparison to age- and sex-matched healthy controls (HC). Secondly, to explore the association of MAIT cells with symptom duration and disease activity.

Methods Consecutive axial SpA patients from the Groningen Leeuwarden axial SpA (GLAS) cohort without active peripheral arthritis, inflammatory bowel disease, psoriasis or uveitis were included. Patients with active infections or current use of biologics were excluded to rule out possible influence on the presence of circulating MAIT cells. Disease activity was assessed using ASDAS, BASDAI, and serum CRP levels.

The frequencies and absolute numbers of circulating MAIT cells were examined in peripheral blood of all studied samples by 5-color flow cytometry. Immediately after sampling, EDTA-blood was stained with anti-CD3, anti-CD8, anti-TCRVa7.2, anti-CD161, and anti-TCRgd. After staining, the cells were washed, fixed, and analyzed immediately on FACS. MAIT cells were identified phenotypically as CD3⁺CD8⁺TCRγδ^-Vα7.2⁺CD161^high cells.

Results Of the 41 included axial SpA patients, mean age was 46±16 years, 73% were male, mean symptom duration was 23±14 years, and 78% were HLA-B27 positive. Mean ASDAS was 2.6±1.0, mean BASDAI was 4.4±2.5, and median CRP was 3 (range 2–30). 70%, 54% and 37% of axial SpA patients had ASDAS ≥2.1, BASDAI≥4 or CRP≥5, respectively. HC had exactly the same age and sex distribution.

Both the percentages and absolute numbers of circulating MAIT cells were comparable between axial SpA patients and HC (Figure 1). In axial SpA patients, absolute numbers of MAIT cells correlated negatively (rho=-0.339) with symptom duration. No significant associations were found between MAIT cells and disease activity, except for a negative correlation (rho=-0.332) between frequency of MAIT cells and BASDAI (Table 1). There were no significant differences in MAIT cells between axial SpA patients with and without active disease according to ASDAS, BASDAI or CRP.

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Conclusions In this homogeneous group of axial SpA patients with only axial disease, the presence of circulating MAIT cells did not differ from age- and sex-matched HC. No strong association was found between circulating MAIT cells and symptom duration or disease activity.

References

1. Gracey et al. Ann Rheum Dis 2016;75(12):2124–32.

2. Hayashi et al. J Rheumatol 2016;43(9):1695–703.

References

Acknowledgements Funding: This research project was supported by an unrestricted grant from Janssen. Janssen had no role in the design, conduct, interpretation, or publication of this study.

Disclosure of Interest None declared