Passive cutaneous anaphylaxis and its enhancement by normal IgG.

Rats were injected intradermally with rabbit anti-ovalbumin serum and 3 hours later were challenged intravenously with ovalbumin and Evans Blue dye. Inflammatory lesions were produced within 20 minutes and their size was markedly dose-dependent. Attempts were made to interfere with this passive cutaneous anaphylaxis (PCA) by admixture of normal IgG with the rabbit anti-ovalbumin to measure the relative tissue binding affinities of IgG from various species. It was found that normal IgG from any of the species tested had an enhancing effect on PCA in rats. These immunoglobulins serially arranged in the order of their decreasing enhancing abilities were: bovine>guinea-pig>pig>rat>rabbit>horse>human. The extent and significance of the enhancement increased considerably with increasing concentration of IgG in the test doses. The mechanism of enhancement was investigated and a hypothesis was proposed to explain the phenomenon.