costimulatsiooni

Costimulation refers to signals provided by antigen-presenting cells (APCs) that are necessary, in addition to the primary signal of antigen recognition by T cells, for full T cell activation, proliferation, and survival. The primary signal occurs when the T cell receptor (TCR) on a T cell binds to an antigen presented by MHC molecules on an APC. This interaction alone is generally insufficient to elicit a robust T cell response.

Costimulatory signals are provided by various molecules expressed on the surface of APCs that interact with corresponding receptors on T cells. The most well-characterized costimulatory pathway involves the interaction between CD28 on T cells and CD80 (B7-1) or CD86 (B7-2) on APCs. Engagement of CD28 by CD80/CD86 amplifies TCR signaling, promotes T cell survival by upregulating anti-apoptotic proteins, and influences cytokine production.

The absence of costimulatory signals during TCR engagement can lead to T cell anergy, a state of unresponsiveness, or even T cell apoptosis. This mechanism is crucial for maintaining immune tolerance and preventing autoimmune diseases. Therefore, costimulation plays a critical role in balancing immune activation and tolerance, ensuring that T cells respond effectively to pathogens while avoiding self-reactivity. It is a key determinant of the magnitude and quality of the adaptive immune response.