Immune reactivity to Der p I and Der p II in house dust mite sensitive patients attending paediatric and adult allergy clinics

Summary A comparison was made of immune responses to house dust mite allergens in symptomatic patients from paediatric and adult allergy clinics. IgE‐specific immune reactivity to Dermatophagoides pteronyssinus was examined by Western blotting and, for Der p I and Der p II. by radioimmune dot‐blot using purified allergens. Nineteen mite‐sensitive children (mean age 9 years) and 26 adults (mean age 31 years) were compared. Positive IgE responses by dot‐blot were found to Der p I and Der p II in 79% of children, whereas reactivity was only present in 23% and 19% respectively of adults, and densitometry indicated a weaker response. In children. Western blotting indicated that the majority of the serologic reactivity was directed to Der p II (17/19, 89%) or a 100 kDa fraction whereas in adults, reactivities were generally directed to other fractions with only 15/26 (58%) recognizing Der p II. Consistent with results of others, a fraction corresponding to Der p I was poorly detected on Western analysis despite positive dot‐blots. To determine whether the relative lack of IgE serological immune reactivity in adults was associated with a similar lack of cellular recognition, T‐cell proliferation studies were performed, also using purified allergens. Interestingly, these revealed that cellular responsiveness, without serological reactivity, was present in 29% of subjects to Der p I and 50% to Der p II. Proliferative responses were evident in all individuals with specific IgE.