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.
Suk
K
K
Clinical Research Center, Samsung Biomedical Research Institute, Seoul, Korea.
Hwang
D Y
DY
Lee
M S
MS
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