Antigenic similarities and differences in genus Pityrosporum

Using the indirect immunofluorescence technique no differences were observed in intensity of staining when antisera against Pityrosporum orbiculare and P. ovale or IgG fractions of these were incubated with P. orbiculare and P. ovale cells. However, a weaker reaction was observed with these antisera and P. pachydermatis cells. With IgG fractions the nonspecific fluorescence was minimized. Fungal cells in biopsies from tinea versicolor lesions showed a brilliant staining with the IgG fractions of antisera against P. orbiculare. This investigation indicates a close antigenic relationship between all of the 3 Pityrosporum species. A common antigenicity was found between P. orbiculare and P. ovale cells as well as between P. orbiculare cells from culture and the fungal cells in biopsies from tinea versicolor lesions. This strongly suggests that these 2 species are identical with each other and with the organism found in tissue.