A simple, effective and inexpensive method to highlight antigen-antibody reaction based on liquid-semisolid phase

Identification of the immunological antigen-antibody reaction performed either in liquid phase or in agarose have several limits: antigen excess, low sensitivity, low speed reaction. A new method is described for the antigen-antibody reaction, easy, simple to perform and inexpensive. It is based on a reaction where the specific antibody is mixed with a semi-solid gel on a transparent surface and the antigen to be identified is inoculated into the gel. In this method, an immune precipitate can be shown in just few minutes, obtaining a good sensitivity compared with manual methods such as the Ouchterlony technique and other similar methods. By using albumin, IgG, RBP, transferrin, alpha-2-macroglobulin as antigen, the immune precipitate is formed within 10 min at 2–8 microgram/ml and, after 30 min, at 1–4 microgram/ml may be detected. The display of the immune precipitate is favored by oblique observation on a black background with a perpendicular light illuminating the gel from the bottom upwards. This method also allows a good control of antigen excess, a problem that is instead found in immunoturbidimetric reactions. The method here described has also been tested in serum and urine, and then it can be advantageously used as qualitative or semi-quantitative immunological test in research or diagnostic. Moreover, it could be particularly useful in low resources geographical areas, where an immunoassay that requires the use of dedicated equipment is not economically sustainable. The authors have waived the patent rights to allow the free development of new tests based on this method.