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.
Clinical Research Center, Samsung Biomedical Research Institute, Seoul, Korea.
K
K
Suk
D Y
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Hwang
M S
MS
Lee
D000328:Adult; D000595:Amino Acid Sequence; D001323:Autoantibodies / Q000097:blood*; D018076:DNA, Complementary / Q000235:genetics; D003922:Diabetes Mellitus, Type 1 / Q000276:immunology; D005260:Female; D037161:Galectins; D015723:Gene Library; D006801:Humans; D007132:Immunoglobulin Isotypes; D007515:Islets of Langerhans / Q000378:metabolism; D037102:Lectins / Q000235:genetics / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D020033:Protein Isoforms; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
D001323:Autoantibodies; D018076:DNA, Complementary; D037161:Galectins; D007132:Immunoglobulin Isotypes; C105032:LGALS9 protein, human; D037102:Lectins; D020033:Protein Isoforms