Allergenic and biologic activity of commercial preparations of house dust extract

The endotoxin, protein nitrogen unit (PNU) content, and allergenic activity of seven different extracts of house dust were determined. The PNU content varied from 1,600 to 44,000 PNU/ml. The endotoxin content as measured by the limulus assay varied from 450 to 500,000 ng/ml. Pyrogenic activity was present by rabbit fever assay and correlated well with the limulus assay. There was no correlation between endotoxin and PNU content of the different dust preparations. Leukocytes from 15 patients with a clinical history of allergy to dust were used for histamine release studies. The allergenic activity did not correlate with the PNU or endotoxin content of the different house dust preparations. The dust extracts could be divided into three groups according to their activities: three extracts which were the most reactive (30% histamine release with 0.12 to 0.39 PNU/ml), two which were about 20 times less active (4.75 to 6.43 PNU/ml for 30% histamine release), and a final group of two which were about 600 times less active. The leukocytes of three out of 15 patients failed to release histamine with one of these least reactive extracts. The reactivity pattern of five of the dust preparations appeared to correlate, suggesting that the different preparations contained the same allergens. Reactivities of two of the other extracts correlated poorly, and the reactivity of the least reactive sample did not correlate with six out of the seven preparations. Therefore, some dust preparations contain significant endotoxin-like material. Wide variations in the endotoxin, PNU content, allergenic activity, and reactivity patterns of different dust preparations were observed.