T cell proliferative response to mitogen derived from mycoplasma arthritidis in presence of la+ epidermal cells as an accessory cell source

In normal mammalian epidermis, class II molecules are expressed only by bone marrow-derived dendritic Langerhans cells (LC). LCs secrete interleukin-1 (IL-1) and are the critical accessory/stimulator cells required for epidermal cell-induced allogeneic and antigen specific T-cell activation. Keratinocytes, which constitute the majority of epidermal cell, have also been shown to secrete IL-1. These cells are induced to express class II molecules in a variety of skin diseases and certain experimental conditions associated with lymphocyte infiltrations into the skin. The T cell proliferative response induced by a mitogen from both cultures of Mycoplasma arthritidis (MAS) is dependent upon the presence of class II antigen-expressing accessory cells (AC). Therefore, the objective of this study was to determine whether class II antigen-expressing keratinocytes could serve as MAS. The results demonstrate that MAS-induced T cell proliferation responses occure in the presence of either LCs or class II antigen-positive keratinocytes. Therefore, control of the MAS response is mediated at the level of ACs, which express the appropriate class II molecules.