Secretion of microbicidal alpha-defensins by intestinal Paneth cells in response to bacteria

Paneth cells in mouse small intestinal crypts secrete granules rich in micr obicidal peptides when exposed to bacteria or bacterial antigens. The dose- dependent secretion occurs within minutes and alpha-defensins, or cryptdins , account for 70% of the released bactericidal peptide activity. Gram-negat ive bacteria, Gram-positive bacteria, lipopolysaccharide, lipoteichoic acid , lipid A and muramyl dipeptide elicit cryptdin secretion. Live fungi and p rotozoa, however, do not stimulate degranulation. Thus intestinal Paneth ce lls contribute to innate immunity by sensing bacteria and bacterial antigen s, and discharge microbicidal peptides at effective concentrations accordin gly.