Figure 1.

Schematic representation of nicotinamide adenine dinucleotide (NAD⁺) utilizing pathways inside the T cell and their overall effect on T cell response. CD38 is the major mammalian NAD⁺ glycohydrolase (NADase) which metabolizes NAD⁺ and generates cyclic ADP-ribose (cADPR), which promotes T cell activation and proliferations through facilitating Ca²⁺ signaling. CD38 expression also depletes NAD⁺ level and hence affect the enzymatic activity of different NAD⁺ consuming enzymes like Sirt1, PARP1, and ART2.2, which play pivotal role in T cell fate determination.