Immunity of Molluscs

IMMUNITY OF MOLLUSCS

  • The immune system of molluscs such as oysters, clams and mussels, consists only of innate immunity and lacks adaptive immunity.
  • Shells, mucus and epithelia which are external barriers of mollusks constitute the first line of defense against pathogens and parasites. The second, internal line of defense are the cellular and humoral hemolymph components.

Humoral components

  • Lysosomal enzymes - β-glucuronidase, acid and alkaline phosphatase, lipase, aminopeptidase and lysozyme
  • Lectins- Agglutinins, fibrinogen-related proteins (FREPS), and C-type lectins, and antimicrobial peptides.

These components help in the recognition of pathogens and parasites by marking them for destruction via opsonization which involves the binding of an opsonin, eg., antibody to a receptor on the pathogen's cell membrane or by directly killing.

Cellular components

  • Cellular components of the haemolymph (a fluid of crustaceans and insects similar to the blood in higher vertebrates), hemocytes (blood cells), play a central role in the innate immune responses of molluscs.
  • Hemocytes consists of two types of cells namely,
  • Hyalinocytes - Small cells with cytoplasm containing few or no granules. These cells are similar to vertebrate monocytes and macraphages.
  • Granulocytes - Large phagocytic cells containing abundant numbers of cytoplasmic granules. It is involved in phagocytosis, pathogen-induced oxidative burst, production and release of nitric oxide and lysosomal enzymes.
Last modified: Sunday, 18 September 2011, 5:27 AM