Panethceller

Paneth cells, also called Panethceller, are specialized secretory epithelial cells of the small intestine. They sit at the base of the crypts of Lieberkühn, with the highest density in the proximal small intestine (duodenum and proximal jejunum) and fewer in the ileum; they are generally absent from the colon.

Morphology: Paneth cells are tall, columnar cells with prominent eosinophilic secretory granules packed basally. Upon secretion, these granules release a repertoire of antimicrobial proteins into the crypt lumen, including α-defensins (cryptdins) such as HD5 and HD6, lysozyme, and secretory phospholipase A2.

Functions: They contribute to innate immunity by directly killing bacteria and shaping the intestinal microbiota. They also help maintain the stem cell niche in the crypt base by providing signaling molecules, notably Wnt3, epidermal growth factor (EGF), and Notch ligands such as Dll4, which support Lgr5+ intestinal stem cells.

Regulation and clinical relevance: Paneth cell activity is influenced by microbial signals and host genetics. Mutations in NOD2, a pattern recognition receptor linked to Crohn's disease, are associated with reduced α-defensin expression in Paneth cells and increased susceptibility to intestinal inflammation. Paneth cell dysfunction or loss is linked to ileal Crohn's disease, and Paneth cell metaplasia can occur in chronic inflammatory conditions.

Origin and history: Paneth cells differentiate from intestinal stem cells within the crypts and contribute to ongoing crypt homeostasis. The term honors Johann Paneth, a 19th-century anatomist.