Lymph Node Physiology
- Lymph Nodes are essentially gathering points at which Antigen Presenting Cells (APCs) can display their collected antigens to T-cells which may specifically recognize these antigens. By gathering at a particular location the probability of an encounter between an antigen and a T-cell which recognizes it is increased. In addition, lymph nodes also serve the mundane purpose of filtering the lymph of any particulate matter that may have entered the fluid prior to its draining into the blood stream.
- Antigen Presenting Cells (APCs)
- The Antigen Presenting Cells in lymph nodes are of two basic types. The first are cells of the innate immune system such as macrophages and Dendritic Cells which have phagocytosed material at their tissue of origin and traveled to the lymph node via lymphatic vessels. The second type are in fact B-cells which have encountered material that binds their B-cell Receptor, internalized the putative microbe, and are displaying its degradation products on its surface.
- T-cells continuously circulate through the lymph node and sample the displayed antigens. If they cannot recognize any displayed antigens they simply exit the node and travel to another. If their T-cell Receptor does recognize an antigen, the T-cells engage in an elaborate molecular communication with the presenting cell which may have a variety of outcomes. Ultimately, this communication sets the stage for the development of Humoral Immunity or Cell-mediated Immunity.