The serum from 75% of the patients with cystic fibrosis (C.F.) who had a positive prick test in their skin to at least one or more antigens, together with elevated concentrations of total serum IgE, also gave strong immediate PCA reactions in the baboon skin to Aspergillus fumigatus, bovine serum albumin and egg albumin. Of the C.F. patients, 37% also had elevated serum specific IgE to A. fumigatus whereas only 8–10% had either raised specific IgE or PCA reaction to Dermatophagoides pteronyssinus. Abolition of the PCA activity by incubating the C.F. sera or sputum at 56°C suggested that the reaginic antibody was IgE rather than IgG4. PCA reactions to a number of allergens could be detected in both the C.F. sputum and saliva.
Several of the C.F. heterozygotes had a strongly positive history of allergy and a significant number of these heterozygotes had an elevated serum total IgE as well as positive PCA to Timothy grass pollen or to D. pteronyssinus similar to the patients with asthma or hay fever. Three C.F. patients who died gave strong prick test reactions to several allergens and their sera also had raised serum IgE and positive PCA to at least three different allergens, suggesting that immediate hypersensitivity is of some significance in patients with C.F.