Analysis of the lymphocyte transformation response to Pityrosporum orbiculare in patients with tinea versicolor.

Lymphocyte transformation responses to Pityrosporum orbiculare were compared in tinea versicolor patients and normal subjects with respect to the number of antigen responsive cells (ARC) present, the first generation lymphocyte response (FGLR), and the magnitude of the total response. A modest, but statistically significant decrease in the magnitude of the lymphocyte transformation response to P. orbiculare was found in the tinea versicolor group and appeared to be accounted for by a similar decrease in the number of ARC to the organism in this group. There did not appear to be any significant rearrangements in the later phases of the lymphocyte transformation response in the tinea versicolor group. Significant enhancement of the response was not obtained using indomethacin, cimetidine or removal of adherent cells. Therefore, in spite of long standing contact wih P. orbiculare and evidence from previous studies of elevated antibody titres against it, patients with tinea versicolor appear to have diminished lymphocyte transformation responses to this organism, apparently due to decreased numbers of cells that are initially responsive to its antigens.