The cellular response in the human skin tuberculin reaction was studied with immunohistochemical double-staining techniques in frozen sections of skin biopsies taken 6 h to 8 days after intradermal PPD injections. Cell infiltrates were observed from day 2 onwards and increased in size up to 4 days. Most of the infiltrating cells reacted with anti-Leu 3a (T 'helper/inducer' phenotype) antibodies. In contrast to normal epidermis, not only Langerhans cells but also keratinocytes expressed HLA-DR antigens from day 4 onwards. The induction of HLA-DR antigens on keratinocytes may be secondary to T-cell activation. Since the HLA-DR expression on keratinocytes appeared late in the tuberculin reaction, the function may be to suppress rather than enhance the immune response.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.