Differential quantification of SIgA and SC by two-directional rocket method.

The two-directional rocket method, a newly modified method for quantitative immunoelectrophoresis, was used as the assay for separating SC and SIgA, which have identical antigenicity but differ in mobility. This method proved to be sufficiently simple and sensitive to enable simultaneous assay of SC and SIgA in saliva. The method employs electrophoresis into antibody-containing agarose/agar gel in the presence of heparin-Ca EDTA. The height of the precipitation peaks formed in two directions is proportional to the concentration of the antigens. Concomitant use of agarose which has little electroendosmosis and agar which has high electroendosmosis facilitated cathodic migration of SIgA. Transfer of SC from beta-region to alpha 1-region without influencing the mobilities of SIgA, albumin or IgG was obtained by addition of heparin-Ca EDTA to agarose/agar gel. This effect of heparin-Ca EDTA is vulnerable to changes of pH of the gel, but is almost completely independent of change in composition or concentration of the gel. The function of heparin as a polyanion may be resonsible for it. Carbamylation of antibody was used to accelerate a clear-cut resolution of the cathodic rockets. This technique was found to be a method of choice for analysis of SIgA and SC in large numbers. In using this method as a screening assay for detection of primary immunodeficiency, by studying saliva samples collected from 3 month old infants on the occasion of regular check-up over a 2 year period, two cases of isolated IgA immunodeficiency and two cases of hypoglobulinaemia were discovered in 12,000 infants.