costimulointi

Costimulation refers to a process in immunology where the activation of immune cells, particularly T cells, requires signals from at least two distinct receptors. The primary signal, often delivered through the T cell receptor (TCR) binding to an antigen presented by an antigen-presenting cell (APC), is insufficient on its own to elicit a full T cell response. A second, costimulatory signal is necessary to prevent anergy, which is a state of unresponsiveness, and to promote T cell proliferation, differentiation, and effector function.

Common costimulatory pathways involve interactions between surface molecules on T cells and APCs. A well-studied example is the B7 family of molecules (like CD80 and CD86) on APCs binding to CD28 on T cells. This CD28-B7 interaction is crucial for robust T cell activation. Other costimulatory molecules, such as ICOS, OX40, and 4-1BB, play roles in different phases of the immune response and in shaping the type of T cell effector function generated.

The absence of costimulatory signals during T cell activation can lead to tolerance or anergy, which is a critical mechanism for preventing autoimmunity. Conversely, the presence of appropriate costimulatory signals is essential for mounting effective immune responses against pathogens and for the development of memory T cells. Understanding costimulatory pathways is vital for developing immunotherapies, such as those used in cancer treatment and for managing autoimmune diseases. Modulating these pathways can either enhance immune responses or suppress them, depending on the therapeutic goal.