CD40 is a member of the TNF receptor family expressed by APCs and B cells whereas its ligand, CD40L (CD154), is expressed by activated T cells.
CD40 – CD40L Pathway
GITR – GITRL Pathway
Glucocorticoid-induced TNFR-related protein is an activating receptor on the surface of T cells and other immune cells, binding to its ligand GITRL.
CD137 – CD137L Pathway
CD137 is an activating receptor binding to CD137L, expressed on natural killer (NK) cells & T cells, therefore triggering innate & adaptive immunity.
TIM-3 – Galectin-9 Pathway
T cell immunoglobulin & mucin-3 (TIM-3; HAVcr-2) is an immune checkpoint receptor involved in the suppression of both innate & adaptive immune cells.
PD-1 [CD279]/PD-L1 [CD274] Pathway
![PD-1 [CD279]/PD-L1 [CD274] Pathway](https://www.caltagmedsystems.co.uk/information/wp-content/uploads/pd-1-600x400px-600x300.png "PD-1 [CD279]/PD-L1 [CD274] Pathway")
The PD-1/PD-L1 or PD-L2 signalling pathway is a negative regulatory mechanism that inhibits T cell proliferation and cytokine production.