The haemolymph of the cockroach, <I>Blaberus discoidalis</I>, contains multiple lectins, designated BDL1, BDL2, BDL3 and GSL, each with different carbohydrate specificities. Both these endogenous, as well as the exogenous lectins, Con A, WGA and HPA, have been shown to induce an enhanced phagocytic response by <I>B. discoidalis</I> plasmatocytes. Thus, the mannose-specific lectins (BDL1 and Con A) both increased the phagocytosis of baker's yeast and <I>Escherichia coli</I>, whereas the G1cNAc/Ga1NAc-specific lectins (BDL2, WGA and HPA) induced the phagocytosis of <I>Bacillus cereus </I>and <I>E. coli. </I>The β-1,3-glucan-specific lectin (GSL) and the Ga1NAc-specific BDL3 only enhanced the phagocytosis of yeast and <I>B. cereus</I>, respectively. The presence of putative receptors for all the phagocytosis-enhancing lectins on the plasmatocytes, was demonstrated using FITC-labelled exogenous lectins to probe the surface of the haemocytes for suitable carbohydrate moieties. When <I>B. cereus</I>, a Gram-positive bacteria, was incubated with an equivalent concentration of lysozyme to that found in the cell-free haemolymph of <I>B. discoidalis</I>, the opsonic activities of BDL1, BDL2 and the exogenous lectins were altered. The G1cNAc-specific lectins, BDL2, WGA and HPA, all exhibited a reduction in the level of enhanced phagocytosis, attributable to the degradation of the peptidoglycan layer surrounding the bacteria, while the mannose-binding lectins, BDL1 and Con A, induced an increase in the phagocytic rate, due to exposure of mannose residues on the surface of <I>B. cereus</I>. These results demonstrate, for the first time in insects, that multiple endogenous lectings, in the cockroach haemolymph are capable of acting as non-self recognition molecules, in a manner analogous to antibodies in the vertebrate immune system.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:636665 |
| Date | January 1998 |
| Creators | Wilson, R. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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