T-cell co-stimulatory signaling

T-cell co-stimulatory signaling is a critical biological process required for the full activation, proliferation, and survival of T lymphocytes following the recognition of an antigen by the T-cell receptor (TCR) (StatPearls, 2023). This "second signal" is primarily mediated by the interaction between the CD28 receptor on T-cells and its ligands, CD80 (B7-1) and CD86 (B7-2), on antigen-presenting cells (APCs) (NIH, 2022). Beyond the canonical CD28 axis, other co-stimulatory pathways include members of the tumor necrosis factor receptor (TNFR) superfamily, such as OX40 (CD134), 4-1BB (CD137), and GITR, as well as the Ig superfamily member ICOS (Nature Reviews Drug Discovery, 2018). In the context of disease, dysregulation of these pathways can lead to autoimmune disorders or allow tumors to evade immune surveillance (PubMed, 2021). Therapeutically, co-stimulatory signaling is targeted in two main ways: inhibition of the pathway (e.g., using CTLA-4-Ig fusion proteins like abatacept) to treat rheumatoid arthritis and prevent transplant rejection, or activation of the pathway (e.g., using agonistic antibodies against 4-1BB or OX40) to enhance the immune response against cancer (DrugBank, 2024). However, modulating these pathways carries significant risks, including the potential for severe cytokine release syndrome or systemic autoimmunity, as seen in the clinical trial of the CD28 superagonist TGN1412 (Wikipedia, 2024).

Other names

T-cell co-stimulationSecond signalCD28-mediated signalingCo-stimulatory pathway

Drugs modulate T-cell responses by either blocking co-stimulatory interactions (e.g., CTLA-4-Ig binding CD80/86 to prevent CD28 activation) to induce immunosuppression, or by acting as agonists to co-stimulatory receptors (e.g., 4-1BB, OX40, CD27) to enhance T-cell effector function and anti-tumor immunity.