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Sialic acid specific lectin Pjlec isolated from serum of the freshwater crab Paratelphusa jacquemontii served as an antigen for the production of immunoglobulin (Ig) in Balb/c mice sera. Enzyme-linked immunosorbent assay (ELISA) of mice anti-sera with Pjlec lectin affirmed the induction and production of antibody. Anti-Pjlec antibody was isolated from the antisera of mice by Protein A Sepharose affinity chromatography and checked for purity by immunoblot with lectin. Mass spectrometry (MS/MS) of papain digethe peptide sequence of antigen binding fragment (Fab) and fragment crystallizable (Fc). Coatingsted anti-Pjlec revealed of anti-Pjlec to the target cell, rabbit erythrocyte failed to enhance in vitro phagocytosis in the crab. However, inoculation of anti-Pjlec in the hemolymph of the crab elicited in vitro phagocytosis. Proteins in hemocyte lysate supernatant (HLS) were separated by electrophoresis failed to immunoblot with Pjlec or anti-Pjlec. Peptide sequences of trypsin digested lectin protein appeared homologous to deuterostome chordate. The protostome crab that lack the ability to synthesize sialic acid however bind to sialic acid a deuterostome sugar to suggest the complexity in innate immune system of invertebrates. The application of lectin and its antibody require further study on application of pathological conditions associated with alterations in sialylated cell surface.

Hemocyanin is a copper containing protein and its role in the immune function of phenoloxidase (PO) activity was investigated in the giant freshwater prawn Macrobrachium rosenbergii. Hemocyanin, sedimented by ultracentrifugation from the plasma appeared on polyacrylamide gel electrophoresis (PAGE 7%) on Coomassie Brilliant Blue and bathocuproine sulfonic acid stain as four copper containing proteins of molecular masses 50, 60, 114 and 325kDa. Accordingly, on diethylaminoethyl-cellulose anion exchange column hemocyanin separated into four proteins designated as MrHc1, MrHc2, MrHc3 and MrHc4 with electrophoretically (PAGE) determined molecular masses of 60, 114, 50 and 325kDa respectively. The reduction of proteins in sodium dodecyl sulphate (SDS)-PAGE revealed that MrHc1 and 3 were monomeric for 60and 50kDa respectively, MrHc2 dimeric of 56 and 58kDa subunits and MrHc4 appeared with three subunits of 74, 76 and 78kDa. The PO activity was determined in plasma, hemocyanin and the four separated hemocyanin proteins in vitro using L-3,4-dihydroxyphenylalanine (L-DOPA) at pH7.5, 25°C and appeared elicited by exogenous activators such as trypsin, SDS, cell wall components of bacteria and polysaccharide laminarin. This study clearly demonstrated hemocyanin as the major copper containing protein in the plasma of M. rosenbergii with potent PO activity.

A new lectin was purified to electrophoretic homogeneity from pronase treated human serum by a single-step of affinity chromatography on concanavalin A-Sepharose 4B. The isolated lectin agglutinated five types of vertebrate RBC, with highest titer against hen RBC. This activity was independent of divalent cations, insensitive to EDTA and specific to mannosamine, glucosamine as well as galactosamine. Purified lectin gave a single symmetrical peak in its native form with a molecular mass estimate of 6kDa in FPLC analysis and 6.5kDa by MALDI-TOF MS. SDS-PAGE analysis of the lectin revealed that it is a homo-oligomer of a 3kDa subunit protein. Isolated lectin did possess both, hemagglutinating and phenoloxidase activities, but did not exhibit any antibacterial or antifungal activities. In addition, this lectin could oxidize all nine different phenolic substrates tested, with hydroquinone proving to be the best among them. Phenoloxidase inhibitors namely, phenylthiourea and tropolone inhibited this oxidation activity.

The lectin, Pjlec isolated from the hemolymph of the freshwater crab Paratelphusa jacquemontii hemagglutinated (HA) with mice, rabbit and rat erythrocytes. However, the lectin failed to agglutinate neraminidase treated asialylated erythrocytes showing its sialic acid specificity. The poyacyrlamide gel electrophoresis of lectin yielded 310 kDa proteins, on sodium sulphate dodecyl (SDS) gel appeared as a tetramer with subunits of 76 kDa. The observation of in vitro phagocytosis in granular hemocytes of lectin opsonized rabbit erythrocyte by Transmission electron microscopy (TEM) showed the release of lytic vesicles by exocytosis prior to engulfment. The Pjlec lectin also showed an ability to oxidize L-3, 4 dihydroxyphenylalanine (L-DOPA) and in hemocyte lysate preparation (HLS) was enhanced on reduction with SDS and on proteolytic cleavage with trypsin. The lectin appeared to have a regulatory role in activation of enzyme activity associated with phagocytosis and melanin formation.

A lectin with insecticidal property against the stored product pest, Callosobruchus maculatus was successfully isolated from the seeds of Canavalia virosa using standard affinity chromatography. The isolated molecule typically behaved like a lectin in its characteristics. It agglutinated indicator red blood cells (RBC) in its native as well as enzyme treated conditions. The enzyme treated RBC types exhibited a very high hemagglutination (HA) titre values and this property of isolated molecule behaved like arcelin, the lectin-like molecules reported from several species of Phaseolus. As a characteristic feature of a lectin, the isolated molecule effectively inhibited the agglutination of indicator RBC types with simple and complex carbohydrates including glycoproteins. This nature of the isolated molecule also relate with characteristic feature of arcelin isoforms in inhibiting HA activity with complex glycoproteins as reported in many studies. Most interestingly, the present study disclosed trehalose as a potent inhibitor of C. virosa lectin. Therefore, feeding insect pests on the lectin like arcelin could serve as antibiosis factor/anti-insect activity. The molecular characteristics of this isolated molecule and its mass studies too revealed its homology with arcelin, arcelin-1, 2 and 6 isoforms of P. vulgaris and lectin from Canavalia cathartica, C. lineata and C. brasiliensis.