Antimicrobial Peptides. An ancient immune system. Antimicrobial peptides: What are they?. Small proteins of cationic charge involved in host innate immune defense. Antimicrobial peptides: Where are they?. In everything from Amoebas to Humans (incl. Bacteria), Abundant in vertebrates in:
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An ancient immune system
The principal defense molecules secreted by Paneth cells are alpha-defensins, also known as cryptdins.
Paneth cells are stimulated to secrete defensins when exposed to bacteria (both Gram positive and negative types) or bacterial products (lipopolysaccharide, muramyl dipeptide and lipid A).
In addition to defensins, Paneth cells secrete lysozyme and phospholipase A2, both of which have clear antimicrobial activity.
This battery of secretory molecules gives Paneth cells a potent arsenal against a broad spectrum of agents, including bacteria, fungi and even some enveloped viruses (gastrointestinal barrier).
Immunohistochemistryshowing Cryptidin 4 in Paneth cell secretory granules (A,B). C and D are the
controls to the experiment to show specificity (peimmune serum/preadsorption).
! They are chemotactic.
274, 26249-26258, 1999
Immunohistochemical staining of BNBD-12. Cytospin preparations of peripheral blood leukocytes (A and B) and bone marrow cells (C and D) were incubated with anti-BNBD-12 IgG (A and C) or preimmune IgG (B and D). A, peripheral leukocytes. All cells shown are neutrophils except the three eosinophils (E). B, negative control staining of leukocytes using preimmune IgG as the first antibody. C, BNBD-12 immunoreactivity in neutrophilic precursors. A spectrum of cells at different stages of maturation is shown. MB, myeloblast; PM, promyelocyte; MC, myelocyte; MMC, metamyelocyte; NB; neutrophilic band. D, Staining of bone marrow cells using preimmune IgG as the first antibody.
but can also be de novo synthesised upon stimulation
with e.g. E.coli/LPS, triggering through Toll-like Receptors.
Mice with genetically engineered deficiency of a metalloproteinase (needed for extracellular cleavage and activation of a-defensins) show increased susceptibility to bacterial infection
In a mouse model of septicemia, LL-37 binds to and neutralises LPS and protects against endotoxic shock.
role in protection from periodontal disease by inhibiting protease of B. gingivalis
Epithelial antimicrobial peptides in host defense against infection. Review.
Respir Res 2000, 1:141-150