Relative antigenicity of P. orbiculare and C. albicans

In lymphocyte transformation studies using optimal concentrations of P. orbiculare and C. albicans extracts, positive responses were found in 31 of 32 normal human subjects to the former and 44 of 49 to the latter. The overall degree of sensitivity to extracts of the 2 organisms as judged by stimulation ratios was not significantly different. The organisms did not appear to cross-react in lymphocyte transformation tests, and in individual human subjects tested with both organisms, a strong response to one did not correlate with a strong response to the other. Extracts of neither organism contained substances suppressive of lymphocyte transformation. P. orbiculare extracts appeared to be significantly less antigenic than those of C. albicans, whether tested against naturally-sensitized humans or artificially-sensitized guinea pigs even though the same amount of protein was extractable from each organism. Therefore, these studies indicate that P. orbiculare has been as successful as C. albicans in producing sensitization against its antigens in the general human population. However, P. orbiculare appears to be significantly less antigenic than is C. albicans, a finding which might be related to the relative lack of inflammation in lesions produced by P. orbiculare, and the rather high incidence of chronic tinea versicolor as compared to chronic mucocutaneous candidiasis.