CD43, also known as Leukosialin and Ly48, is a 125 kD sialoprotein (glycosylated protein) expressed from 1.2 kBase mRNA in bone marrow-derived cells. This occurs early in development. Cells expressing CD43 include gamma/delta T cells, macrophages, mature B cells, and dendritic cells. CD43 functions as an anti-adhesive surface molecule, promoted by antibody cross-linking, that releases the trailing edge of the cell during locomotion to allow movement of the cell body towards the lamellipodia. The intracellular distribution of CD43 is determined by binding to moesin, an intracellular membrane protein, which is in-turn bound in some manner to the actin cytoskeleton. Defects with CD43 function and expression retard cellular locomotion, resulting in a wide range of immune disorders. Wiscott-Alderich syndrome, and the varying degrees of its severity, is related to the dysregulation of CD43 expression.