Quantitative determination of human alpha 2-macroglobulin by means of immunoelectrophoresis in antibody-containing gel

Abstract

The present investigation was undertaken in order to evaluate the applicability of Laurell's method of quantitative immunoelectrophoresis to the routine determination of α 2-macroglobulin concentration in human serum. It was found that over the whole range of concentrations used a straight-line relationship existed between the amount of antigen and the surface area of the corresponding precipitin peak. When peak heights were recorded instead of areas, the calibration curve was rectilinear only over a limited range of concentrations. Depending upon the amount of α 2 m present in the sample, the standard deviation of the determinations ranged from 1.2 to 2.5% of the mean, when peak areas were used, and from 0.0 to 2.2% of the mean if peak heights were employed. In a large series of measurements on the same sample (0.35 μg α 2 m content) the error appeared to be 1% for heights and 1.4% for areas. In a series of unselected 34 sera the α 2 m content was evaluated both using the single radial immunodiffusion technique of Mancini and the immunoelectrophoretic technique of Laurell, with a very satisfactory agreement. The lowest amount of precipitate on which reasonably accurate surface measurements could be carried out corresponded to 0.035 μg of antigen with the Mancini method as well as with the area-recording modification of the Laurell method, and to 0.14μg with the height-recording version of Laurell's method.