Expression of cellular adhesion molecules in Langerhans cell histiocytosis and normal Langerhans cells.

Langerhans cell histiocytosis (LCH) is characterized by lesions with an accumulation and/or proliferation of Langerhans cells (LCs). Little is known of the etiology and pathogenesis of LCH. Although the relation between the LCH cell and normal LCs is currently uncertain, the localizations of the LCH cells is considered aberrant when compared with normal LCs. Cellular adhesion molecules (CAMs) are known to play an important role in a variety of cell functions such as migration, antigen presentation, and activation. Aberrant migration of LCs may play a role in the pathogenesis of LCH. We investigated CAMs in 27 tissue specimens of 20 patients with LCH retrieved from our files during the last 15 years. LCH cells showed strong expression of CAMs such as CD54, CD58, and the beta 1-integrin alpha 4 that are upregulated during activation of normal LCs. In contrast, CAMs not found on normal LCs could be demonstrated in a number of cases on LCH cells like CD2, CD11a, and CD11b. Also CD62L, normally expressed only by epidermal LCs, could be detected on LCH cells. The integrins alpha 5 and alpha 6, not or only weakly found on epidermal LCs and highly expressed by activated LCs, could not be demonstrated on LCH cells. Our data suggest abnormal expression of CAMs on LCH cells that may contribute to abnormal migration of LCs in LCH. The aberrant phenotype of LCH cells has characteristics of both epidermal LCs and activated LCs and may be indicative of an arrested state of activation and/or differentiation of LCs.