CD28B7Achse

The CD28-B7 axis is a critical component of the immune system's regulation of T cell activation and immune response. It involves the interaction between the costimulatory receptor CD28 on T lymphocytes and its primary ligands, the B7 family proteins (also known as CD80 and CD86), expressed on antigen-presenting cells (APCs).

CD28 is a surface receptor found on most T cells and provides essential costimulatory signals that promote T cell activation, proliferation, and survival following antigen recognition. Its engagement with B7 molecules enhances cytokine production, including interleukin-2 (IL-2), and facilitates the development of effective adaptive immunity. Conversely, the interaction also plays a role in maintaining immune tolerance and preventing autoimmunity.

The B7 family comprises two main molecules: B7-1 (CD80) and B7-2 (CD86), both of which can bind to CD28. While CD86 is typically expressed constitutively at lower levels and rapidly upregulated upon activation, CD80 expression is more tightly regulated and appears later in immune responses. These molecules can also interact with CTLA-4, a homologous receptor that transmits inhibitory signals, thereby modulating the immune response and maintaining immune homeostasis.

Therapeutically, the CD28-B7 pathway has gained interest in the context of immunotherapy. Blockade of this axis with drugs such as abatacept (CTLA-4-Ig) is used to treat autoimmune diseases by dampening excessive immune responses. Conversely, strategies aiming to enhance the pathway are explored to boost immune responses against infections and tumors.

Overall, the CD28-B7 axis is a crucial regulator of T cell-mediated immunity, balancing activation and tolerance to sustain immune homeostasis and prevent pathological conditions.