Allergenic and antigenic cross-reactivities of group IX grass pollen allergens

The allergenic and antigenic cross-reactivities between a major recombinant Poa pratensis (Poa p) IX allergen, rKBG8.3, and its corresponding proteins of different grass pollens were examined. Immunoblotting of the proteins of thirteen different grass pollens using anti-rKBG8.3 antibodies indicated that Poa p IX-like proteins are present in ten other grass pollens, albeit in variable amounts and polymorphic forms. These proteins ranged in size from 20 to 88 kDa in different grass pollens. The percent relative binding determined for each grass pollen extract using allergic human sera showed a significant correlation (r = 0.891) with that of anti-rKBG8.3 antiserum. Moreover, there was a strong association (r = 0.901) between the Kentucky bluegrass extract and rKBG8.3 with respect to their inhibition of the binding of human IgE antibodies to allergens in grass pollen extracts. Taken together, these results suggest that the allergenic and antigenic epitopes of the Poa p IX-related proteins in some but not all grass pollens are similar in structure and specificities. It is concluded that the group IX allergens constitute a major family of homologous proteins in several grass pollens.