Humoral Factors of Innate Immune Response

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Humoral Factors of Innate Immune Response

  • The system of humoral factors of innate immunity comprises the enzymes, soluble proteins and peptides that promote non-specific immune reactions in biological fluids of the host (in plasma, saliva and other mucous secretions, breast milk, tears, etc.).
  • The humoral innate immune response consists of naturally occurring antibodies (NAb), pentraxins and the complement and contact cascades
  • Strong antimicrobial effects are demonstrated by the numerous group of so-called acute phase proteins present in plasma. Their concentrations increase the following inflammation.
  • Among them are C-reactive protein, mannose-binding lectin, alpha-2-macroglobulin, ceruloplasmin, ferritin, fibrinogen, serum amyloid components, and some others.
  • Their common mechanisms of activity include tight non-specific binding to microbial cells with bacterial arrest in the site of inflammation, prevention of microbial adhesion, activation of phagocytosis (opsonization), activation of complement system via lectin and alternative pathways, iron deprivation of bacterial cells, inhibition of microbial enzymes and toxins.
  • C-reactive protein and serum amyloid components are members of the pentraxin protein family regarded as a special group of pattern-recognition receptors.
  • Similar antimicrobial activities are characteristic for fibronectin plasma protein.
  • Lactoferrin is the iron-binding glycoprotein of biological fluids. Its antimicrobial action is related to high iron-binding capacity. Iron-deprived bacteria stop their growth and reproduction.
  • Cationic enzyme lysozyme (or muramidase) destroys glycosidic bonds between N-acetyl-glucosamine and N-acetyl-muramic acid within bacterial cell wall peptidoglycan (or murein). As a result, it causes the lysis of bacterial cells.
  • In addition, a great number of antimicrobial peptides of low molecular weight releases from the host cells into various biological fluids. Among them are defensins and cathelicidins from leukocytes, beta-lysins of platelets, histatins and cystatins from saliva and some others.

References

  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3576926/#:~:text=The%20humoral%20innate%20immune%20response,prevention%20and%20control%20of%20disease.