An anti-human μ chain monoclonal antibody: use for detection of IgM antibodies to Toxoplasma gondii by reverse immunosorbent assay

Abstract A precipitating anti-human μ chain monoclonal antibody (designated Tibi 82 McAb) was produced by the cell fusion technique. This McAb (isotype: IgG1κ) reacted by radioimmunoassay with all 10 human IgM proteins tested. In contrast, no reactivity was observed with IgG, IgA, IgE, λ and κ chains. 19 S IgM proteins were precipitated by Tibi 82 McAb using the Ouchterlony method under standard conditions. Hence specificity of this McAb for the Cμ2 domain was characterized by inhibition of precipitin reactions using human IgM fragments. Despite its narrow specificity for the Cμ2 domain, such a McAb coulb be used for IgM capture in the detection of specific IgM to Toxoplasma gandii employing the IgM immunosorbent agglutination assay (IgM-ISAGA). Tibi 82 McAb was compared with 3 anti-human IgM polyclonal reagents in the routine analysis of 117 sera. With 2 of them, a correlation coefficient of 0.976 was obtained and Tibi 82 McAb was more sensitive than the third polyclonal reagent tested. The IgM-ISAGA technique was shown to be reproducible using Tibi 82 McAb and similar anti-human μ chain McAbs could permit the wider development of reverse immunosorbent methods for the detection of specific IgM in various infectious diseases.