Labeling immunoelectrophoresis: a general method for increasing the sensitivity of rocket immunoelectrophoresis with 125I-labeled anti-antibodies.

In a new procedure, rocket immunoelectrophoresis is performed at pH 8.7 with rabbit antibodies and 5% polyethyleneglycol 6000 in the agarose gel. After the pH in the gel has been changed to 5 the nonprecipitated immunoglobulins are electrophorsed out of the gel simultaneously with the electrophoresis of 125I-labeled swine antibodies against rabbit IgG into the gel. The latter antibodies tag the rabbit IgG, which is not present only in the precipitates. The radioactive precipitates are visualized by autoradiography. The method permits quantification of antigens down to an amount of approximately 0.5 ng; well-defined rockets are not formed below this limit. Compared to conventional protein staining with Coomassie brilliant blue, this represents an increase in sensitivity of up to 20 times.