Quantitative Determination of Serum Immunoglobulins in Antibody-Agar Plates

The antibody in agar plate test has proved valuable for the quantitative measurement of individual serum immunoglobulins. With this technique, specific antiserum is mixed uniformly in an agar gel plate. Antigen containing solutions are placed in small antigen wells cut in the agar. A concentric ring of antigen: antibody precipitate forms around the antigen well. By graphically comparing the ring diameters with those of appropriate standards, the protein concentration of the test sera can be determined. The probable error in measurement of normal serum immunoglobulins is ±10%. This procedure has been used to quantify protein concentrations as low as 0.003 mg/ml. Multiple samples can be easily tested and less than 0.1 ml of sample is required. The mean immunoglobulin levels in 20 normal human sera were found to be 12.4 mg/ml for IgG (7 S γ2-globulins); 2.8 mg/ml for IgA (γ1A or β2A-globulins) and 1.23 mg/ml for the IgM (18 S γ1M-globulins). Type K (I) and Type L (II) immunoglobulins were similarly determined. The results by the antibody-agar plate method are similar to those obtained by the isotopic immune inhibition technique, except for the serum IgA and Type K (I) and Type L (II) immunoglobulin levels. With each of these proteins the values obtained by the isotopic immune inhibition test are higher than those found by the antibody-agar plate test. The basis for this difference is discussed.