CD24 is a 35-45 kD glycosylphosphatidylinositol (GPI)-linked protein also known as heat stable antigen (HSA), BA-1, Ly-52, and nectadrin. It is expressed on the surface of B cells (but not plasma cells), granulocytes, follicular dendritic cells, and epithelial cells. CD24 may play a role in the regulation of B-cell proliferation and maturation. CD24 crosslinking induces a Ca2+ flux in mature B cells. CD24 has been shown to interact with CD62P (P-selectin).