The effect of extracts of champedak (Artocarpus integer) seed lectin on the proliferation of normal human lymphocyte was investigated. The IgA1 binding lectin was demonstrated to stimulate the proliferation of human peripheral blood mononuclear cells. Action of the lectin on enriched T and B cell populations demonstrated T lymphocyte specificity. The lectin was not mitogenic to B lymphocytes. Optimal stimulation of proliferative response was achieved when cells were subjected to 5 days exposure to the crude lectin at 20 micrograms/ml.
Purified lectins from seeds of six distinct clones of Artocarpus integer (lectin C) were shown to be structurally and functionally similar. All lectins comprised of two types of non-covalently-linked subunits with apparent M(r) of 13,300 and 16,000. The lectins appeared to interact with several human serum proteins, with the predominance of the IgA1 and C1 inhibitor molecules. Interaction was not detected with IgA2, IgD, IgG and IgM. The lectin Cs were also shown to precipitate monkey, sheep, rabbit, cat, hamster, rat and guinea-pig serum. Due to their uniform properties, lectin C may provide better alternative to the Artocarpus heterophyllus lectin, jacalin, for use in future investigations.
Current diagnosis of melioidosis is based on bacterial culture and/or serology which is becoming increasingly useful. An IgM-ELISA using heat-killed whole cells of Pseudomonas pseudomallei was developed and compared with an indirect haemagglutination technique (IHAT) and an indirect immunofluorescent technique(IFAT). The IgM-ELISA using a P:N ratio of > or = 2 had a sensitivity of 91% and a specificity of 96%. All 3 assays were further used in a seroepidemiological survey amongst different groups of patients and healthy individuals. It was found that the IFAT performed better than the IHAT, detecting antibodies to P. pseudomallei in 6% of diabetics, 5% of pyrexics, 8% of pregnant women and 3% of farmers. For the same groups the IgM-ELISA detected antibodies in 1% of pyrexics, 8% of pregnant women and a further 14% of farmers. The IgM-ELISA was found to be sensitive and useful for the serological diagnosis of acute melioidosis.
The effect of Artocarpus integer lectin (lectin C) on the functional activity of guinea-pig complement was investigated. Purified and crude extract of lectin C from six cultivars of Artocarpus integer seeds were found to consume complement and thus decreased the complement-induced haemolytic activity of sensitized sheep erythrocytes. The change in the complement-mediated haemolytic activity was significantly decreased when incubation of the lectins was performed in the presence of melibiose. The reversal effect of the carbohydrate, which is a potent inhibitor of the lectin's binding to O-linked oligosaccharides of glycoprotein, demonstrate involvement of the lectins interaction with O-glycans of glycoproteins in the consumption of guinea-pig complement.