Membrane ecto-ATPase on epidermal Langerhans cells

Epidermal Langerhans cells (LC) possess a plasma membrane Mg(++)- or Ca(++)-dependent ecto-ATPase (mATPase), the function of which is not known. On the other hand, extracellular ATP (ATPo) has been shown to cause a rapid increase in cell-membrane permeability for selected cells, thus inducing the entry of exogenous substances, leading eventually to cell death. ATPo has also been shown to be a mediator of T cell-mediated cytotoxicity. We have observed human LC to be resistant to the permeabilizing effects of ATPo when compared to cultured human keratinocytes and J774 macrophages. In addition, our preliminary evidence in vitro suggests that mATPase on LC may provide protection against the lytic effects of ATPo. Finally, we propose that this latter mechanism may also operate in vivo.