Collaborative clinical assay of the biological potency of allergen skin-test extracts.

A multicentre collaborative clinical trial has been made at one centre in each of six countries to decide if the potency of allergen extracts can be determined satisfactorily by skin-prick tests in man. Although there was considerable variation in potency of antigen when determined in different patients, if a sufficiently large group (n = 54) of persons were tested, it was shown to be feasible to compare potencies of sequential batches of the same specificity, and also of antigens of different specificities. It was shown that batches of mite extract were weaker than that of a grass pollen, but it proved to be a simple matter to adjust the concentration to give the same biological potency.

Familial human short-term sensitizing (IgG S-TS) antibody.

Skin tests on a middle-aged English housewife (the initial case) with a history of seasonal grass pollen rhinitis and asthma showed strong immediate and late reactions to grass pollens. Early in the grass pollen season, 1976, RAST showed normal levels of IgE antibodies in the serum. Passive transfer in Rhesus monkey skin was also negative for heat-labile IgE but gave a very vigorous reaction for short-term sensitizing heat-stable IgG antibody (IgG S-TS Ab). Skin tests and studies on sera from other members of the family showed that another five also formed IgG S-TS Ab, and indicated that the ability to form this antibody was familial. One member of the family had only an immediate reaction on skin testing, and much IgE to grass pollen. Towards the end of the grass pollen season the IgE titre in the initial case had been tripled and the IgG S-TS Ab had disappeared. By September the specific IgE titre had risen even further.