ISSN:
1432-0878
Keywords:
Exocytosis
;
Phagocytosis
;
Cell cooperation
;
Prophenoloxidase
;
Invertebrate immunity
;
Pacifastacus leniusculus
;
Carcinus maenas
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary The role of exocytosis in the cellular defence reactions of arthropods was investigated using in vitro cultures of isolated haemocytes (blood cells) from the freshwater crayfish Pacifastacus leniusculus, and the shore crab Carcinus maenas. In both species, activated lysates of those cell types that contain the prophenoloxidase activating system (granular cells of crab and crayfish and semigranular cells of crayfish) were found to induce degranulation (exocytosis) of semigranular and granular cells. A cell lysate, in which the prophenoloxidase system was kept inactive, did not have this effect. Limited degranulation of granular cells of crab was also induced by lipopolysaccharides as has earlier been shown for crayfish semigranular cells. The phagocytic capability of semigranular cells from crayfish was lost after exocytosis induced by the Ca2+ ionophore A23187, and under no conditions were the granular cells of crabs or crayfish seen to ingest bacteria in vitro. An opsonic function for the attaching proteins of a β1,3-glucan-activated haemocyte lysate was demonstrated using the phagocytic hyaline cells from crabs. Phenoloxidase appeared to lack opsonic properties. We suggest that, in crustaceans, opsonization takes place through hierarchically stimulated exocytotic release, and biochemical activation of the prophenoloxidase activating system: first from lipopolysaccharide-sensitive cells (semigranular cells of crayfish or granular cells of crabs) and then from granular cells, triggered by the initially released and activated prophenoloxidase system. Finally, “sticky” proteins of the activated prophenoloxidase system coat the invader, rendering it susceptible to the phagocytes (hyaline cells in both crab and crayfish and, to a lesser extent, semigranular cells of crayfish). These processes would, together, constitute a cellular communication pathway not previously demonstrated for invertebrates.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00218085
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