Effect of mixing allergenic extracts containing Helminthosporium, D. farinae, and cockroach with perennial ryegrass.

Allergenic extracts used for immunotherapy often contain mixes of different allergens. Studies have shown that certain allergenic extracts contain enzymes that can cause a decrease in grass pollen allergenicity when mixed with grass extracts. Glycerin and buffered saline with phenol (BSP) extracts containing Helminthosporium interseminatum, D. farinae, and cockroach were mixed with perennial ryegrass extracts and analyzed 7, 30, 60, and 90 days after mixing to determine the mixing effect of these extracts on the ryegrass pollen potency. Analysis was performed using RAST inhibition, SDS-PAGE and, to determine biologic potency, a quantitative intradermal skin test technique. All tests showed significant decreases in ryegrass potency when mixed with Helminthosporium and cockroach. This decrease was not seen with the D. farinae mix. Glycerin seemed to have some protective effect. Even in the situation showing the most decrease in ryegrass potency (Helminthosporium mixed with ryegrass in a BSP extract), the resulting extract still contained an estimated biologic potency of 10,000 AU/mL. This may explain why such mixes, which have been used clinically for many years, appear to give adequate therapeutic results. The study also suggest that clinicians may be well advised not to mix grass pollen extracts with extracts that may contain proteolytic enzymes.