Passive cutaneous anaphylaxis: improvement of quantitative analysis by radioactively labelled antigen.

Experiments were performed to improve the quantitative analysis of passive cutaneous anaphylaxis (PCA) by labelling the antigen with radioactive iodine. After intradermal injection of antibodies and intravenous administration of labelled antigen in rats a close correlation was found between the radioactivity measured in skin biopsies and the amount of antigen as well as the amount of antibodies. This direct dependence makes it possible to improve quantitatively the reading of PCA test results. A quantitative correlation was also found when radioactivity is measured over the skin by scanning procedures. Therefore it is not necessary to cut out skin biopsies. Thus the same test animal can be used several times, which minimizes biological variations.