INSITU IDENTIFICATION OF LYMPHOCYTE-T SUBSETS AND HLA-DR EXPRESSING CELLS IN THE HUMAN-SKIN TUBERCULIN REACTION

Abstract

T lymphocytes subsets and HLA-DR expressing cells were studied with an immunohistochemical double staining technique in frozen sections of human skin 6, 48 and 96 h after intradermal PPD [purified protein derivative] injections. The number of lymphocytes reacting with monoclonal Leu 1 antibodies (all mature peripheral T cells) increased with time. The majority of the T lymphocytes at 48 and 96 h reacted with Leu 3a (helper/inducer phenotype) antibodies and a few with Leu 2a (suppressor/cytotoxic phenotype) antibodies. Apposition of T lymphocytes of both subsets to HLA-DR expressing cells occurred in the dermis and in the epidermis. The study gives a morphological picture of the cell-mediated immune reactions in delayed type of hypersensitivity consistent with in vitro experiments on proliferative responses to soluble antigens.