innateImmuneSensoren

Innate immune sensors are pattern‑recognition receptors that detect conserved microbial or danger‐associated molecular patterns and initiate the first line of host defense. They recognize distinct molecular signatures through diverse structural domains. Toll‐like receptors (TLRs) are the most characterized family; they are expressed on many cell types, including epithelial, dendritic and macrophage cells, and are localized either to the plasma membrane or to endosomal compartments. TLRs sense bacterial lipopolysaccharide, flagellin, unmethylated CpG DNA, RNA viruses and other microbial ligands. NOD‑like receptors (NLRs) reside in the cytoplasm and bind peptidoglycan fragments and bacterial proteins; many NLRs activate inflammasomes, leading to caspase‑1 activation and the maturation of IL‑1β and IL‑18. RIG‑I‑like receptors (RLRs) detect viral double‑stranded RNA in the cytosol and trigger type I interferon production. C‑type lectin receptors (CLRs) bind carbohydrates on pathogens and modulate phagocytosis and cytokine secretion.

Activation of an innate immune sensor initiates intracellular signaling cascades that converge on transcription factors such as NF‑κB, AP‑1 and interferon regulatory factors (IRFs). The resulting transcriptional program drives the production of cytokines, chemokines, antimicrobial peptides and the up‑regulation of costimulatory molecules, thereby coordinating innate and adaptive immunity. In addition to pathogen recognition, many sensors detect damage‐associated molecular patterns released by stressed or dying cells, linking tissue injury to immune responses.

Dysregulation of innate immune sensors can contribute to inflammatory, autoimmune and neurodegenerative diseases. Conversely, therapeutic manipulation of sensor signaling pathways is being explored to enhance vaccine efficacy, control infections and treat chronic inflammatory disorders. Thus, innate immune sensors serve as critical nodes that translate external and internal danger cues into coordinated immune responses.

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