CD28signalering

CD28 signalering refers to the activation pathway initiated by the CD28 receptor, a co-stimulatory molecule expressed on the surface of T lymphocytes. This signaling pathway is essential for full T cell activation, proliferation, survival, and cytokine production. CD28 interacts primarily with B7 molecules (CD80 and CD86) present on antigen-presenting cells (APCs), providing a necessary second signal that complements antigen recognition by the T cell receptor (TCR).

Upon binding to its ligands, CD28 undergoes conformational changes that trigger intracellular signaling cascades involving kinases such as phosphoinositide 3-kinase (PI3K) and downstream activation of Akt. These pathways promote metabolic changes, gene transcription, and cytoskeletal rearrangements necessary for T cell responses. CD28 signaling enhances the production of interleukin-2 (IL-2), a cytokine critical for T cell proliferation and differentiation.

In addition to promoting activation, CD28 signalering increases the expression of survival proteins like Bcl-xL and inhibits apoptotic pathways, ensuring sustained immune responses. It also influences the balance between effector and regulatory T cell functions, affecting immune tolerance and autoimmunity.

Dysregulation of CD28 signaling can contribute to immune deficiencies or hyperactivations, such as autoimmune diseases or cancer. Therapeutically, modulation of CD28 pathways has been explored in immunotherapy; for instance, agonist antibodies can enhance immune responses, while antagonists may suppress unwanted immune activity.

Overall, CD28 signalering is a fundamental component of T cell biology, coordinating the immune response by integrating co-stimulatory signals with antigen recognition to achieve effective and controlled immunity.