Signaling is fundamental to how cells sense and respond to their environment—but in immune cells, those signals must be precisely amplified to mount an effective defense against invasive threats. New research by immunologists in Germany is shedding light on how that amplification occurs in T cells, revealing a key molecular mechanism that helps trigger immune responses—and may also contribute to inflammatory conditions.

Writing in Science Signaling, researchers at the University Medical Center Hamburg-Eppendorf identified a crucial step in the production of a “second messenger,” an internal signal that relays and amplifies messages received at the cell surface. Because external signaling molecules cannot enter the cell, second messengers translate those cues into powerful intracellular responses.

In T cells, that process depends on NAADP (nicotinic acid adenine dinucleotide phosphate), a molecule that drives calcium (Ca²⁺) signaling—an essential step in T cell activation. Without it, T cells cannot become the effector cells needed to fight serious threats, such as infections or cancer.