immunoreceptor

An immunoreceptor is a receptor on immune cells that detects molecular structures associated with pathogens, damaged cells, or immune signals, and translates recognition into cellular responses. Immunoreceptors can initiate activating or inhibitory signals and shape both innate and adaptive immunity. They may recognize pathogens directly, as pattern recognition receptors do, or recognize antibodies or antigen-bound complexes as antigen receptors of B cells and T cells.

Major families include pattern recognition receptors such as Toll-like receptors, NOD-like receptors, RIG-I-like receptors and C-type lectin receptors; antigen receptors such as the B cell receptor (BCR) and T cell receptor (TCR); Fc receptors that bind the Fc portion of antibodies; and complement receptors. Immunoreceptors can be located on the cell surface or in endosomal compartments where they encounter ligands.

Many immunoreceptors contain immunoreceptor tyrosine-based activation or inhibition motifs (ITAMs or ITIMs) in their cytoplasmic tails or signal through adaptor proteins. Ligand engagement activates kinases and downstream signaling pathways such as NF-kB, MAPK, and calcium flux, leading to functional responses including cytokine production, phagocytosis, cytotoxicity, or antibody generation.

Dysregulation of immunoreceptors can contribute to infections, inflammatory diseases, and autoimmunity, while therapeutic modulation of these receptors—through agonists, antagonists, or monoclonal antibodies—plays a major role in contemporary medicine.