| Summary: | Using hybridoma technology, six monoclonal antibodies (mAbs) against a serum lectin designated BDL1 from the cockroach, <I>Blaberus discoidalis</I>, were produced and characterised. These antibodies, namely, 1G12, 1H4, 3B1, 6B4, 11E1, 13E10, were isotyped as IgG1. Immunoaffinity chromatography using purified mAbs against BDL1 immobilised on CNBr-activated Sepharose 4B matrix was successfully employed to purify BDL1 from the serum of the cockroach, <I>Blaberus dicoidalis</I>. BDL1-like lectins were also detected in the sera of two other cockroach species, namely, <I>Blaberus craniifer</I> and <I>Gromphadorhina portentosa</I>, and were purified by immunoaffinity chromatography. BDL1 and BDL1-like lectins purified by immunoaffinity chromatography have molecular masses of <I>ca</I>. 65 kDa and 32 kDa under non-reducing and reducing conditions, respectively. Immunocytochemistry with mAbs demonstrated that BDL1 is present in the haemocytes of <I>B. discoidalis</I>. Its presence in the haemocytes was further confirmed by Western blotting. BDL1 was not found in other tissues such as fat body, Malphigian tubules, midgut, testis and ovary. Immunocytochemical staining also showed that BDL1-related components are present in the haemocytes from several other cockroach species, namely, <I>Blaberus craniifer, Gromphadorhina portentosa, Periplaneta americana, </I>and <I>Leucophaea maderae</I>. Immunoaffinity purified BDL1 was found to agglutinate a range of animal erythrocytes as well as bacteria and yeast <I>in vitro</I>. It also enhanced the phagocytosis of of nonself particles including rabbit erythrocytes, <I>E. coli</I> and the baker's yeast <I>Saccharomyces cerevisie</I> by the plasmatocytes of the cockroach, <I>Blaberus discoidalis</I>, in an <I>in vitro</I> phagocytosis assay. In addition, BDL1 enhanced the activation of prophenoloxidase system by laminarin. All these results indicate that BDL1 is a multifunctional factor in the haemolymph of the cockroach, <I>Blaberus discoidalis</I>, and plays important roles in the immune responses of this insect.
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