The mucosal immune system plays a critical role in gut immunity. When B cells undergo differentiation into plasma cells, they synthesize dimeric immunoglobulin A (IgA), which is subsequently secreted into the sub-epithelial compartment of the lamina propria. To infiltrate the intestinal lumen, IgA must traverse the epithelial barrier. This translocation is facilitated by epithelial cells that consistently express a receptor known as the polymeric immunoglobulin receptor, which exhibits a strong affinity for a particular segment of the immunoglobulin complex. Identify the specific component this receptor binds to