effectors

Effectors are components that carry out a response to a signal in a biological system. In general, an effector translates a regulatory cue into a functional change, such as altered metabolism, movement, secretion, or gene expression.

In physiology, effectors are the tissues or organs that execute commands from the nervous or endocrine systems. Skeletal muscles and glands are classic examples, responding to motor or autonomic signals with contraction or secretion; smooth muscle and cardiac tissue can also act as effectors in certain contexts.

In immunology, effector cells are mature immune cells that perform defense functions. Examples include cytotoxic T lymphocytes that kill infected cells, plasma cells that secrete antibodies, and effector macrophages that phagocytose pathogens. Helper T cells can also have effector functions in coordinating responses.

In cell signaling and molecular biology, effector proteins are molecules that enact the final response within a cell. They may be enzymes, transcription factors, ion channels, cytoskeletal proteins, or other targets. Signaling pathways regulate these effectors via second messengers, phosphorylation, or protein-protein interactions to produce changes in activity, localization, or gene expression.

Some contexts describe effectors produced by pathogens, known as effector proteins, which manipulate host cellular processes to promote infection. Plants and animals monitor these effectors with immune receptors, leading to defense responses.