CD44 expression in normal and inflamed skin.

CD44 is the principal cell surface receptor for hyaluronate. In non-inflamed skin, CD44 expression is limited to the cell membrane of eccrine coil cells. The distribution on these cells is asymmetric, with intense staining on the dermal side and little staining on the luminal side of the coil cell. In skin containing a pathologic process, either inflammatory or neoplastic, CD44 expression can be widespread on the membranes of keratinocytes and on infiltrating lymphocytes in the vicinity of the process. Diverse roles have been proposed for CD44 and largely involve aspects of cellular adhesion in one setting or another. CD44 may identify a more mobile, proliferating keratinocyte that is responding to local injury. In eccrine coil, the stable presence of CD44 on the non-luminal surface of secretory cells indicates an undefined function for CD44 in the generation of eccrine sweat.