Mammalian cells release adenosine triphosphate (ATP) into the extracellular space, where it activates purinergic receptors through both autocrine and paracrine signaling. Multiple families of ectonucleotidases catalyze the stepwise conversion of extracellular ATP to ADP, AMP, and adenosine. All populations of adaptive immune cells express distinct repertoires of purinergic receptors and ectoenzymes, enabling them to modulate cellular functions and engage in intercellular crosstalk with neighboring cells. Activation of purinergic receptors initiates diverse downstream signaling cascades, including extracellular Ca²⁺ influx, alterations in intracellular cyclic AMP (cAMP) levels, and stimulation of mitogen-activated protein kinase (MAPK) pathways. These signaling events regulate critical immune functions such as cell migration, antigen recognition, and the orchestration of adaptive immune responses to both internal and external threats. In this brief overview, we highlight key purinergic signaling mechanisms that govern the complex functional landscape of adaptive immune cells.