Purification and characterization of natural antibodies that recognize a human brain lectin

Animal Galectins and Plant Lectins as Tools for Studies in Neurosciences

Lectins are proteins or glycoproteins of non-immunological origin capable of reversibly and specifically binding to glycoconjugates. They exist in free form or associated with cells and are widely distributed in nature, being found in plants, microorganisms, and animals. Due to their characteristics and mainly due to the possibility of reversible binding to glycoconjugates, lectins have stood out as important tools in research involving Neurobiology. These proteins have the ability to modulate molecular targets in the central nervous system (CNS) which may be involved with neuroplasticity, neurobehavioral effects, and neuroprotection. The present report integrates existing information on the activity of animal and plant lectins in different areas of Neuroscience, presenting perspectives to direct new research on lectin function in the CNS, providing alternatives for understanding neurological diseases such as mental disorders, neurodegenerative, and neuro-oncological diseases, and for the development of new drugs, diagnoses and therapies in the field of Neuroscience.

The effect of galectin-1 on the differentiation of fibroblasts and myoblasts in vitro

Normal murine dermal fibroblasts implanted into the muscles of the mdx mouse, a model for Duchenne muscular dystrophy, not only participate in new myofibre formation but also direct the expression of the protein dystrophin which is deficient in these mice. We have reported that the lectin galectin-1 is implicated in the conversion of dermal fibroblasts to muscle. In the current work we confirm the presence of galectin-1 in the medium used for conversion. Furthermore we report that exposure of clones of dermal fibroblasts to this lectin results in 100% conversion of the cells. Conversion was assessed by the expression within the cells of the muscle-specific cytoskeletal protein desmin. We also investigate the effects of galectin-1 on cells of the C2C12 mouse myogenic cell line and on primary mouse myoblasts. Exposing both transformed and primary myoblasts to the lectin resulted in an increase in fusion of cells to the terminally differentiated state in both types of cultures. Galectin-1 does not cause the myogenic conversion of murine muscle-derived fibroblasts.

Natural autoantibody to galectin-9 in normal human sera

Antibodies to certain self-antigens are detected in normal individuals as well as in patients with autoimmune diseases. Natural autoantibodies found in normal human sera are thought to act as an immune regulator, a functional controller of specific proteins, or the first-line defense against pathogenic microorganisms. In the course of screening human pancreatic islet cDNA library with human sera, we found that autoantibodies to galectin-9 and its unique isoform are present in normal healthy individuals. Galectin-9 antibody was detected in all 44 human sera tested by the immunoprecipitation assays, suggesting a widespread presence of galectin-9 autoantibodies in humans. The reactivity of the sera to galectin-9 was not inhibited by lactose or endoglycosidase treatment, indicating that the reactivity was not due to a nonspecific lectin-carbohydrate interaction. We also demonstrated by RT-PCR that galectin-9 and its isoform are expressed in a variety of human tissues such as pancreatic islets, liver, lung, and tonsils as well as HeLa and Jurkat cell lines. Thus, although it has been reported previously that human galectin-9 is expressed mainly in immune cells and tissues, the current work suggests that the expression of galectin-9 and its isoform is not tissue-restricted and natural autoantibodies against them are present in normal human sera. The significance of these autoantibodies needs to be studied further.

The immune system can affect learning: chronic immune complex disease in a rat model

Evidence is presented that the immune system can affect central nervous system functioning, leading to changes in learning. Immune complex disease is induced in rats and their behavior tested using a Lashley maze. Significant differences in behavior were found between the animals with high disease activity and those with low disease activity and the non-disease controls. These changes were not due to uremia and are most likely due to the immune response. There is some evidence immune complex deposits in the choroid plexus may play some role, but not the sole or major role in the behavioral changes. This provides a model by which immunologic processes can cause neuropsychiatric manifestations in autoimmune diseases like lupus, as well as showing that immune processes can affect behavioral functioning.

Lectin histochemistry of astrocytic tumors and in vitro characterization of lectin-induced modifications on the proliferation of the SW1088, U373 and U87 human astrocytic cell lines

The role of lectins as biosignalling molecules or as markers of human astrocytic tumors remains relatively unexplored. The aim of the present work is to investigate (1) whether or not human astrocytic tumors express specific glycans, evidenced experimentally by means of lectin histochemistry, and (2) whether, in turn, these lectins can significantly modulate astrocytic tumor cell proliferation. Using a cell image processor, we therefore began by quantitatively measuring the histochemical binding pattern of 5 lectins (WGA, PNA, PHA-L, GSA-IA4 and Con A) in 5 astrocytomas, 5 anaplastic astrocytomas and 5 glioblastomas. Secondly, we measured the influence of these 5 lectins on the proliferation of 3 astrocytic tumor cell lines (SW1088, U373 and U87) growing in vitro as monolayers. Cell proliferation was assessed by means of the colorimetric MTT assay. The histochemical lectin staining markedly varied intra- and inter-group. However, some constant results were obtained. Indeed, the staining increased markedly from GSA-IA4 and PHA-L through WGA and PNA to ConA in the three histopathological groups. The assessment of cell proliferation demonstrated that WGA, Con A and PHA-L very significantly decreased proliferation in the 3 astrocytic cell lines in a dose-dependent manner. Astrocytic tumor cells in the confluent growth phase were less sensitive to the WGA, Con A and PHA-L lectin-induced effects than cells in the log growth phase. The GSA-IA4 and PNA lectins had globally very weak effects on the proliferation of the astrocytic tumor cell lines. Increasing the fetal calf serum from 1% to 10% in the culture media significantly antagonized the WGA-, Con A- and PHA-L-induced cell proliferation decrease in the 3 astrocytic cell lines. In conclusion, the present data strongly suggest that some lectins (including WGA, Con A and PHA-L) significantly influence the proliferation of astrocytic tumor cells.

Anti-galectin-1 autoantibodies in serum of patients with neurological diseases

The presence of autoantibodies to human brain galectin-1 was investigated in serum from patients with multiple sclerosis, patients with or without evidence of other neurological disorders, and healthy controls, using an ELISA on purified brain galectin-1. Levels of autoantibodies to galectin-1 were significantly higher in patients than in healthy controls. Comparison of levels of anti-galectin-1 and anti-idiotypic antibodies mimicking human brain galectin-1 (L-IgG) showed that the highest levels of autoantibodies were present in patients with low levels of L-IgG. This finding can be explained by hypothesizing that the concentration of autoantibodies to galectin-1 is possibly associated with impairment of the regulation of the immune system.