IgE antibodies to protein and mannan antigens of pityrosporum ovale in atopic dermatitis patients.

Background: Pityrosporum ovale is a common saprophyte on the skin capable of inducing IgE antibody production in atopic dermatitis (AD) patients. Allergens of P. ovale have been examined in several studies, but consensus on them is lacking.
Objective: This study was carried out to obtain more information about the IgE antibody response against P. ovale, including mannan.
Methods: Sera from 64 AD patients and 10 healthy controls were analysed with immunoblotting and the nitrocellulose radio allergosorbent test (RAST) method specifically developed to detect antimannan P. ovale IgE antibodies.
Results: In immunoblotting a total of 39 different IgE stained protein bands were seen. A high molecular weight staining was also seen especially in patients who displayed elevated mannan P. ovale RAST values. The most commonly stained protein bands in immunoblotting were 9 and 96 kD bands with antibodies in 73 and 65% of AD patients who had been positive in commercial P. orbiculare RAST with total serum IgE less than 4000 kU/l. Mannan RAST appeared positive in 77% of them. Positive immunoblotting to either of these bands was seen in 90% and, if added with staining with the 20 kD band, in 100% of these AD patients. A combination of 9 kD IgE staining and mannan P. ovale RAST was positive in 92% of the patients and 96 kD and mannan P. ovale RAST in 85% of the patients.
Conclusion: It is evident that P. ovale has several allergens, the 9, 96 and 20 kD regions being the most important. According to our results mannan is also an important allegen of P. ovale.