Extrafollicular B cell peripheral subpopulations in Sjögren's disease: expansion of DN2 and aNAV B cells

Sjögren's disease (SjD) is an autoimmune condition marked by exocrine gland damage, lymphocytic infiltration, and autoantibody production. Recently, extrafollicular B cells have been implicated in autoimmune diseases, yet their specific role and characteristics within SjD remain largely unknown. Therefore, we aim to evaluate the distribution of atypical memory B cells (aMBCs) in patients with SjD and correlate them with clinical features. Forty SjD patients and 34 healthy subjects (HS) were included. Identification of aMBCs (CXCR5^-CD11c⁺) subsets was performed, then expression of CD21 and CD38 were assessed in aMBCs subpopulations. SjD patients exhibited a systemic expansion of extrafollicular B cells, including aNAV, DP NAV, and DN2, DN3, and DN4 populations (P < 0.001). ANCOVA revealed that DN2 expansion is uniquely independent of chronological aging (P = 0.006). Analyzed CD19⁺ B cells using high-dimensional t-SNE and biaxial gating showed that aMBCs displayed heightened CD38 expression, signaling an activated phenotype primed for plasma cell differentiation. Furthermore, inverse correlations between DP NAV and USM frequencies and clinical scores (clinESSDAI, SSDDI) suggest possible sequestration within salivary glands or functional exhaustion. This pathogenic signature, manifesting as early as the naïve stage, underscores the aNAV-DN2 axis as a central hallmark of B-cell dysregulation in SjD.