Analysis of cross-reactive allergens from American and German cockroaches by human IgE

Serum from atopics hypersensitive to the American cockroach were examined for their specific IgE to American and German cockroaches by the fluoroallergosorbent test (FAST). Of 44 sera tested, 86.4% (38/44) contained IgE to American and German cockroaches, and 13.6% (6/44) were found to be positive for American cockroach alone by FAST. Nine individual sera containing IgE antibodies to both cockroaches were used to analyze the cross-reacting allergens in the crude American and German cockroach extracts by FAST inhibition and immunoblotting. FAST-inhibition studies showed various degrees but similar inhibition of binding of human IgE to solid-phase American cockroach extract. Proteins from both cockroach extracts were separated on SDS-PAGE followed by immunoblotting, and the results showed considerable heterogeneity in the IgE-binding patterns with each of the cockroach extracts for the same nine individual sera. Components with apparent molecular weights of 60, 52, 49, 38, and 12 kDa from both the American and German cockroaches were able to bind IgE antibody. These results suggest the presence of cross-reactive allergens in the American and the German cockroaches.