FCRL5 and autoimmune disease: Interestingly, we observed a set of upregulated proteins in AP+ B cells, namely CXCR3, CD307e (FCRL5), CD95, CD86, partially CD11c, and decreased CD21 and CD23 (Figure 3C), which are considered key phenotypic markers of a B cell subset, known as age-associated B cells (ABCs), extrafollicular or atypical B cells in chronic infection and autoimmune diseases.26