The Poly Ig Receptor, also known as the polymeric immunoglobulin receptor or pIgR, is a protein that plays a crucial role in the immune system. It is primarily found in epithelial cells, which are the cells that line various surfaces of the body such as the respiratory and digestive tracts.
The main function of the Poly Ig Receptor is to transport immunoglobulins, also known as antibodies, across the epithelial cell layer. Immunoglobulins are a type of protein produced by plasma cells in response to the presence of foreign substances, such as bacteria or viruses. These immunoglobulins are essential for the immune system to recognize and neutralize these foreign invaders.
The Poly Ig Receptor binds to immunoglobulins found in the lamina propria, a layer of tissue located beneath epithelial cells. It then transports these immunoglobulins into the lumen, or cavity, of the epithelial tissue. This process is called transcytosis. Once inside the lumen, the Poly Ig Receptor cleaves, or cuts, the immunoglobulin, leaving a portion known as the secretory component attached to the remaining immunoglobulin fragment.
The secretory component provides protection to the immunoglobulin, preventing it from being degraded by enzymes in the lumen. This ensures that the immunoglobulin retains its structure and function when it is released into the body cavity or secreted onto the epithelial surface. Overall, the Poly Ig Receptor is vital for the transport and protection of immunoglobulins, thereby enhancing the body's immune response.
