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Microparticle-enhanced nephelometric immunoassay (Nephelia) for immunoglobulins G, A, and M

ML Cuilliere, P Montagne, T Bessou, R el Omari, D Riochet, P Varcin, P Laroche, P Prud'homme, J Marchand and O Flecheux
Immunology Laboratory, Faculty of Medicine, Vandoeuvre-les-Nancy, France.

Covalent binding of gamma chains of IgG, whole IgA, and mu chains of IgM on polyfunctional hydrophilic microspheres (MS) yields MS-Ig conjugates, usable as reagents in new microparticle-enhanced nephelometric immunoassays (Nephelia).

The principle of the assays is inhibition by free analyte (IgG, IgA, and IgM) of agglutination of the MS-Ig conjugate with specific antiserum, the light scattered by the aggregates being measured with a nephelometer.

The immunoglobulin assays developed are easy to perform (single-step assays, no washing or phase separation) and sensitive (high dilution of biological samples to exclude interferences and pretreatment).

Analytical recovery results (95.4-101.2%) and correlations with generally used commercial assays (r = 0.86-0.98) indicate that the assays are accurate for large concentration ranges of immunoglobulins. Precision study gives CVs = 2.8-9.6%. Nephelia appears to be useful for quantifying a large variety of biological molecules.