Immune system and antioxidants, especially those derived from Indian medicinal plants.

During the functioning of the immune system, such as in phagocytosis, reactive oxygen and nitrogen species are generated. If they are left unchecked they can affect the components of the immune system by inducing oxidative damage. This is more so in the elderly or during inflammation where there is excess generation of these reactive species than can be taken care of by the defenses in the form of antioxidants. Dietary supplementation with antioxidants may greatly help in such conditions. There are some indications of possible benefits of antioxidant supplementation. Natural compounds from medicinal plants having antioxidant and immunomodulatory activities have potential as therapeutic agents in this regard. Indian medicinal plants with these activities have been identified and their antioxidant and immunomodulatory effects reviewed. The possible future prospects in this regard are also outlined.

Characterization and biological activities of Chenopodium leaf hemagglutinin (CLH).

A hemagglutinin (CLH) having native molecular mass of 58 kDa and subunit molecular mass of 33 kDa had been purified from the leaves of Chenopodium amaranticolor. The protein agglutinated rabbit erythrocytes and no agglutination was observed with any of the groups A, B or O of human blood. The amino acid composition revealed that CLH was rich in aspartic acid, glutamic acid, glycine and phenylalanine and also significant amount of methionine. The N-terminal amino acid sequence analysis showed that CLH had no homology with any of the plant hemagglutinins studied so far. It was inactive towards human peripheral blood cells but mitogenic for mouse spleen B-lymphocytes. CLH inhibited protein synthesis in rat thymocytes at high concentration. CLH did not inhibit TMV infection of leaves indicating absence of antiviral properties.

Radiolabelled monoclonal antibodies against human cardiac myosin.

Myocardial infarction (MI) can be monitored using several protein markers including human cardiac myosin (HCM). Monoclonal antibodies were raised against HCM by hybridoma technique. Antimyosin antibody producing clones were identified by ELISA and monoclonality was established by limiting dilution. The antibodies were purified, isotyped and their cross reactions with myosin from other species were estimated. All the clones showed negligible cross reaction with rabbit myosin, but reacted with bovine skeletal myosin to different extents (40-100%). The most avid antibody Mab 4G4 which also strongly reacted with rat cardiac myosin, was labelled with 125I using different oxidising agents such as iodogen, chloramine-T and lactoperoxidase. More than 95% pure radiolabelled antibody could be obtained by gel filtration. The immunoreactivity was retained. Mab 4G4 was also labelled with 99mTc using stannous tartrate as the reducing agent. Radiolabelling yield was approximately 60%, the purity was >95%. Both the radiolabelled preparations were tested for biodistribution in rats--both normal and those with induced MI. Approximately 0.7 % of the injected activity/g was found in the infarcted region and the accumulation of activity in the infarcted heart was 1.5 times that in the normal heart. A very high percentage of activity (80%) accumulated in the thyroid. With further optimisation of labelling and use of F(ab')2 fragments, better delineation of the infarct sites may become possible.

Electrokinetic behaviour of subpopulations of T lymphocytes in allografted mice.

In AKR(H-2k) mice transplanted with DBA/2(H-2d) skin grafts, the mean electrophoretic mobilities (EPM) of total lymph node cells (LNC) and T cells were significantly reduced. Subpopulations of T lymphocytes, viz. CD4- (CD8- (CD4+) T cells were obtained by depletion treatment of T cells with monoclonal antibodies specific for these surface antigens and complement. Determination of EPM of these two subpopulations revealed that the electrokinetic change following immunostimulation equally afflicted these two subpopulations. These data thus confirmed that CD4+ as well as CD8+ T cells were activated in MHC unmatched allograft rejection.

Electrokinetic studies on concanavalin A as a tool to probe the surface characteristics of differentiated lymphoid cells.

The redistribution of surface receptors induced by the binding of concanavalin A to different types of lymphoid cells was studied by the techniques of cell electrophoresis and fluorescence microscopy. The cells studied included, splenic lymphocytes from normal healthy as well as terminally leukaemic mice, thymocytes from mice of varying ages from newborns to adults and antigen sensitised or educated lymphocytes. These cells were in different stages of growth and/or differentiation. The nature and especially the behaviour of surface receptors in response to treatment with concanavalin A under capping conditions differed markedly but appeared to be dependent on the differentiational status of the cells. On this basis, the adult thymocytes were found to consist of two sub-populations differing in their proliferative and differentiational status. The proportions of these varied during their ontogenic development. Lymphocytes specifically committed to an antigen bound concanavalin A but were found to be incapable of bringing about the redistribution of the surface receptor-ligand complexes.