Antibodies to cytoskeletal systems in normal human serum

Serum antibodies to cytoskeletal systems were measured by indirect immunofluorescence using human skin fibroblasts as the substrate for actin and vimentin, and HEp2 cells for cytokeratin. IgM concentration in 12 umbilical cord blood was less than 20 mg/dl, but antibody to cytokeratin was detected in samples that contained more than 10 mg/dl of IgM. Sera from 8-year-old pupils had elevated antibody titer to vimentin of IgG, IgM and IgA class and to cytokeratin of IgG and IgM class. Healthy adults had IgM anti-vimentin and anti-cytokeratin antibody at 60 times serum dilution, but other antibodies were lower than 10 times serum dilution. IgG and IgA concentration did not have any correlation with anti-cytoskeletal system antibodies. IgM concentration tended to correlate with IgM antibody titer to vimentin and cytokeratin. With increasing age in adults, antibody to actin of IgG class appeared.