IgE production, antigen-induced airway inflammation and airway hyperreactivity in the brown Norway rat: the effects of ricin.

Ricin has been shown to enhance IgE production in the rat, probably through inhibition of suppressor T lymphocytes. We have studied further the effects of ricin on IgE titre and have determined its effects on antigen-induced airway inflammation and hyperreactivity in the Brown Norway rat. Immunization with ovalbumin (1-100 micrograms, intraperitoneally) produced dose-related increases in serum antigen-specific IgE titre. Ricin augmented the total IgE titre and caused about a 10-fold increase in the peak antigen-specific IgE titre. In sensitized animals, antigen challenge (three times with aerosolized ovalbumin every second day) caused a significant influx of eosinophils and neutrophils and significant airway hyperreactivity 24 hr after the third challenge. In sensitized animals that had also received ricin, the eosinophil and neutrophil influx was further significantly potentiated and a significant influx of lymphocytes also occurred. Thus, there was a relationship between the degree of sensitization and the magnitude of the inflammatory response. However, the enhanced airway inflammation in ricin-treated animals was not accompanied by a further enhancement of airway hyperreactivity. The present study demonstrates that ricin enhances IgE production and augments an antigen-induced inflammatory pathology but does not potentiate antigen-induced airway hyperreactivity.