Expression of GM-CSF receptor by Langerhans' cell histiocytosis cells

Langerhans' cell histiocytosis (LCH) is characterized by the proliferation of large mononucleated cells containing Birbeck granules and expressing CD1a. Recent studies have demonstrated that LCH is a clonal proliferation; however, its aetiology is still unknown. Growth and differentiation of bone-marrow-derived cells are controlled by cytokines. The proliferation, differentiation and activation of normal Langerhans cells are controlled by granulocyte/macrophage colony-stimulating factor (GM-CSF) in vitro. Therefore, GM-CSF could be implicated in the pathogenesis of LCH. Indeed, LCH cells contain GM-CSF, and children with disseminated LCH have an elevated GM-CSF serum level. As a cytokine only acts on cells expressing a specific receptor, we investigated the presence of GM-CSF receptor on LCH cells. Fourteen frozen tissue samples from children with LCH were studied by in situ immunohistochemistry with two mouse monoclonal antibodies specific for the alpha chain of the GM-CSF receptor (CDw116). LCH cells of all the samples were positively stained with both antibodies. This study suggests that GM-CSF may be a growth factor for LCH cells.