Page 61 - Veterinary Immunology, 10th Edition

VetBooks.ir Pathogen-Associated Molecular

Patterns

As described earlier, PAMPs are common, essential, conserved
molecular structures (or patterns) that are produced by a diverse
range of potential microbial invaders. Thus, they include
lipopolysaccharides, peptidoglycans, and nucleic acids.

Bacterial Lipopolysaccharides

Lipopolysaccharides are structural components of the cell walls of
many bacteria, especially Gram-negative ones. They are recognized
by TLR4. TLR4 does not bind LPS directly but only when linked to

three other proteins. These proteins are MD-2 (myeloid
differentiation factor-2), LPS-binding protein (LBP), and CD14. The
CD14 interacts with TLR4 in such a way that it decreases the

specificity of these reactions and enables both rough and smooth
strains of bacteria to be recognized (Fig. 2.7). Binding of LPS to the
CD14/TLR4/MD-2 complex activates macrophages and triggers
cytokine production. The LPS subsequently dissociates from CD14
and binds to lipoproteins, where its toxic activities are lost. CD14

also binds many other bacterial molecules, including
lipoarabinomannans from mycobacteria, mannuronic acid
polymers from Pseudomonas, and peptidoglycans from

Staphylococcus aureus.

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