Haemorrhagic reactions elicited at sites of passive cutaneous anaphylaxis by the intravenous injection of aggregated gamma-globulin.

In guinea-pigs injected intradermally with a small amount of antibody and challenged 2 hours later, by the intravenous route, with a mixture of homologous antigen and aggregated γ-globulin, haemorrhagic reactions of the Arthus type develop at the sites of intradermal sensitization. This effect was obtained with γ-globulins of different species (human, rabbit and horse) by using different techniques for aggregation (heat, mercaptoethanol—urea and bis-diazobenzidine) and was always correlated with the ability of the aggregated globulin to fix complement. Fluorescein labelled aggregates of γ-globulin were detectable in the wall of vessels at sensitized sites. In experiments performed with guinea-pig antibodies, the localizing effect was observed only with γ1, whereas the γ2, Arthus-producing fraction proved completely ineffective. Histamine and histamine liberators are not sufficient for eliciting the effect obtained with sensitizing antibody plus homologous antigen. It is postulated, therefore, that other effects occurring at the site of specific sensitization may also be responsible for the phenomenon.