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[Establishment and evaluation of enzyme-linked immunosorbent assay for measuring human IgM autoantibody to folate receptor].

OBJECTIVE
To establish the method of enzyme-linked immunosorbent assay (ELISA) for measuring human IgM autoantibody to folate receptor.


METHODS
Folate receptor was extracted and purified from the healthy woman placenta. The protein was coated on 96-well plates with a concentration of 5 ng/Μl. Goat monoclonal antibody was used for detecting antibody. Pooled plasma from healthy donors was used to plot the standard curve and the IgM concentration of pooled plasma was defined as 1. We set up an ELISA procedure to measure human IgM autoantibody to folate receptor. The sensitivity, precision, and stability of the method were evaluated. Further, the folate receptor and bovine folate-binding protein were used as the antigen, respectively, to determine the autoantibody levels in 24 healthy individuals and 20 individuals once gave birth to baby with neural tube defects.


RESULTS
The measuring range of the method was from 6.25 × 10⁻⁴ to 8.00 × 10⁻². The lowest IgM level that can be detected was 3.12 × 10⁻⁴. The inter-assay coefficients of variations for samples with high, medium, and low IgM levels were 6.61%,3.50%, and 5.12%, respectively. The intra-assay coefficients of variations were 4.54%, 5.49%, and 5.44%, respectively. The stability test results were considered within acceptable limits. The data from folate receptor-ELISA was significantly higher than that from bovine folate binding protein-ELISA, both in the healthy group (t=-11.9, P<0.001) and in the neural tube defect group (t = 7.35, P<0.001).


CONCLUSIONS
The folate receptor-ELISA method for measuring human IgM autoantibody to folate receptor was successfully established. The method is sensitive, repeatable, and stable.