Increased IL-21 Expression Induces Granzyme B in Peripheral CD5⁺ B Cells as a Potential Counter-Regulatory Effect in Primary Sjögren’s Syndrome

Figure 6

Possible results of interlukin-21 (IL-21) stimulation on B cells. In the presence of CD40 ligation and either a B cell receptor (BCR) or a Toll-like receptor signal, IL-21 stimulation fundamentally promotes B cell activation and differentiation into memory and plasma cells [6]. The combination of IL-21 stimulation and BCR engagement in the absence of CD40 ligation enables B cells to produce and secrete active form of granzyme B (GrB). GrB-producing B cells may acquire antiviral immune function and/or a regulatory function on themselves or other immune cells including T and NKT cells [15]. In the absence of both BCR engagement and T cell help, IL-21 stimulation induces B cell apoptosis [11].