CD32 (FcγRIIB) expression is low on CD21low B cells from systemic sclerosis patients with digital ulcers, interstitial lung disease, and anti-topoisomerase I autoantibodies

Abstract

CD21^low B cells have recently been found increased in SSc-associated digital ulcers (DUs) or interstitial lung disease (ILD). To further characterize CD21^low B cells which encompass autoreactive cells, we analyzed their expression of the inhibitory CD32 receptor in SSc. Peripheral blood mononuclear cells from 27 patients with SSc and 15 age-and sex-matched healthy controls (HCs) were analyzed with multicolor flow cytometry. CD21^low B cells were significantly increased in patients with DUs (51.3%) compared to HCs (28.1%) and in patients with ILD (53.1%) compared to HCs. CD21^lowCD32^low B cells were significantly increased in patients with DUs (23.8%) compared to HCs (4.4%), in patients with ILD (28.4%) compared to HCs, and in anti-topoisomerase I (+) patients (21.5%) compared to HCs and to anti-topoisomerase I (-) patients (2.4%). Autoreactive B cells recognizing Topoisomerase I were predominantly within CD32^low cell fraction. Our study further supports the autoreactive status of CD21^lowCD32^low B cells in SSc patients.

Keywords: Anti-topoisomerase I autoantibody; Autoreactive B cells; FcγRIIB; Interstitial lung disease; Microvasculopathy; Systemic sclerosis.