The heat stability of short ragweed pollen extract and the importance of individual allergens in skin reactivity.

A short ragweed pollen extract that was heated in a boiling-water bath remained skin reactive for some allergic individuals and lost reactivity for others. Comparison of heated and unheated extract by immunodiffusion showed that AgE, AgK, and Ra3 could not be detected in the boiled extract but Ra5 was present. By inhibition of the radioallergosorbent test the concentration of Ra5 remained essentially unchanged, but the concentrations of AgE and Ra3 were greatly diminished. The sera of these ragweed-allergic individuals were analyzed for IgE antibodies to AgE, Ra3, and Ra5. Skin reactivity in 17 ragweed-allergic individuals to the heated extract correlated significantly with the levels of IgE antibodies to Ra5. However, the large number of individuals reacting to the boiled extract indicates that Ra5 is not likely to be the only heat-stable allergen. Skin reactivity of the unheated extract did not correlate with IgE antibody levels to any allergen. The results underscore the importance of individual allergens in the materials used for skin testing.