Studies on the specificity of human IgE-antibodies to the plant proteases papain and bromelain

The sera of seven patients clinically hypersensitive to papain—in one case also to bromelain—and the sera of sixty asthmatic patients with allergies to other inhalant and food allergens were investigated for IgE antibody activity to the plant proteases papain and bromelain and to common allergens by RAST, confirmed in some sera by RAST inhibition. There seems to be a relation between the antibody reactions to papain and bromelain, in several cases also between the reactions to these proteases and to grass pollen and flour. Studies by RAST inhibition showed that papain, bromelain, wheat flour, rye flour, grass pollen and birch pollen mutually inhibit IgE antibody to each antigen; but the degree of inhibition varies among the different sera and allergens. Our results suggest that these allergens from various plants, besides having specific antigenic determinants, also possess similar or even identical antigenically active regions, leading to immunological cross-reactivity.