Sera from 13 patients with positive Pityrosporum ovale skin prick test were analysed with IgE immunoblotting. Both P. ovale and Candida albicans antigens were used to reveal possible crossreactivity of these yeasts. Of the 13 sera, eight sera showed IgE binding to P. ovale and six sera to C. albicans. Simultaneous IgE-binding to both C. albicans and P. Ovale was observed in five of these sera. The most common IgE-binding band pairs were, a 23 kD band of P. ovale and a 27 kD band of C. albicans, as one pair, and a 26 kD band and a 13 kD band, respectively, as another pair. In addition to these protein bands, simultaneous reactivity was observed to C. albicans mannan, a polysaccharide, and to a diffuse high molecular weight component of P. ovale, possibly also a polysaccharide. The five sera with simultaneous IgE-binding were analysed with RAST-inhibition, which revealed presence of crossreacting IgE-antibodies to P. ovale and C. albicans in two of these sera. Crossreacting epitopes were suggested to be located in the mannan polysaccharide of C. albicans and high molecular weight diffuse stain of P. ovale, based on the immunoblotting and RAST-inhibition patterns of the studied sera. Crossreacting sera were pooled and used as an IgE probe in CRIE and Tandem-CRIE. These experiments revealed a fused precipitin line indicating presence of a common structure of P. ovale and C. albicans.
This suggested crossreactivity may imply an interesting phenomenon in atopics who are sensitized by C. albicans growth in the gastrointestinal tract and get exposed by P. ovale growing on the skin. Further studies are thus needed to clarify the clinical significance of these preliminary findings.