The immune system plays a crucial role in identifying and responding to threats, such as infected cells and pathogens, while avoiding harm to healthy cells. A key component in this process is the interaction between T cells and major histocompatibility complexes (MHCs). MHCs are surface proteins found on host cells that present antigens—substances that can provoke an immune response—to T cells. This interaction is essential for T cells to recognize and respond appropriately to threats.
For instance, macrophages, a type of immune cell, display MHCs on their surface. These MHCs present antigens to T cells, specifically helper T cells (also known as CD4 cells). The T cell receptor (TCR) on the helper T cell binds to the MHC-antigen complex, enabling the T cell to initiate a suitable immune response. This process is vital for distinguishing between harmful and harmless cells, ensuring that the immune system targets only those that pose a threat.
There are two major types of MHCs, which will be explored further in subsequent discussions. Understanding the function and types of MHCs is fundamental to grasping how the immune system operates and how it can be harnessed in medical applications, such as immunotherapy and vaccine development.