Prolonged immunotherapy with alum-precipitated pyridine ragweed extracts-a clinical and immunological study

In 18 ragweed hay fever patients who received injections of alum-precipitated pyridine (Allpyral) ragweed extracts in maintenance doses of between 6000 and 8000 P.N.U. at intervals of between two and four months over a two-year period, the prolonged interval did not seem to influence either the clinical response or the tendency to reaction, or result in significant change in immunological tolerance as determined by antibody studies, which included fluorescent antibody assays, as well as hemagglutination and RAST technics.