Materials And Methods A The System IgGIgM

The bare polystyrene latex particles were prepared under emulsifier-free conditions by the two-step procedure [32]. Particles of 900 nm diameter developed in 0.03 mol/L NaCl at pH 7.3 a surface potential of -13.5 mV. The density was 1.045 g/mL. Fully IgG-coated latex particles were prepared by using the conventional procedure. The antigen IgM was provided by Biomerieux at a concentration of 30 IU/mL. One liter of the aqueous phase at pH 7.3 employed to disperse the IgG-coated particles contained 7.2 g Glycocoll, 1.6 g NaCl, and 1.5 g trishydroxyaminomethane. This preparation constitutes the suspending medium of the slide test.

Figure 3 shows the electrophoretic mobility of the system IgG-IgM as a function of the amount of IgM added per gram of IgG-coated latex particles

FIG. 2 Schematic representation of the elementary structure of the link formed by the HCG molecules (b) between two latex particles, one bearing the monoclonal anti-aHCG determinant (a) and the other bearing the monoclonal anti-PHCG determinant (c).

0 2000 4000 6000 8000 10000 Antigen {U.l./g latex)

FIG. 3 Representation of the electrophoretic mobility (pm s-1 V-1 cm) of antibody-coated latex particles as function of the concentration of antigen in the solution for the different systems: IgG-IgM in 0.03 mol/L NaCl at pH 7.3 (□), anti-|3HCG-HCG (O) and anti-aHCG-HCG (O) in 0.05 mol/L NaCl at pH 7.6.

dispersed in the standard solution. Increased surface coverage with IgM molecules strongly decreases the electrophoretic mobility of the coated particles.

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