BOTH DENDRITIC CELLS AND MEMORY T-LYMPHOCYTES EMIGRATE FROM ORGAN-CULTURES OF HUMAN SKIN AND FORM DISTINCTIVE DENDRITIC-T-CELL CONJUGATES

Prior studies of mouse skin in organ culture have shown that dendritic cells selectively emigrate from the explants over 1-3 d, This emigrat ion may model the movements of dendritic cells that can occur in situ, as in transplantation and contact sensitivity, In this study, we cult ured explants of normal human skin that had been removed with a dermat ome, Dendritic cells with characteristic morphology and mixed leukocyt e response-stimulatory activity emigrated, The dendritic cells had the expected phenotype, e,g,, rich in major histocompatibility complex cl ass II and accessory molecules such as B7-1, intercellular adhesion mo lecule-1, and leukocyte function-associated antigen-3, Small lymphocyt es also were present in the emigrated populations and proved to be T c ells exclusively, almost entirely of the TcR alpha beta and memory typ e (CD45RA(weak), CD45RO(+) LFA-3/CD58(+)), with a CD4:CD8 subset ratio of about 2:1, Some of the T cells were bound tightly to the dendritic cells, These conjugates did not dissociate after exposure to trypsin or to calcium- and magnesium-free medium, or during cytofluorography. This made it possible to sort distinct populations of single dendritic cells, single T cells, and conjugates of the two cell types, Conjugat es would continue to form from mixtures of separated dendritic cells a nd T cells in culture, Therefore, cutaneous dendritic cells and memory T lymphocytes emigrate from human skin explants, and some of these ce lls form distinctive conjugates that we hypothesize contribute to immu nologic recall reactions.