WAS and Wiskott-Aldrich syndrome: WASP is a hematopoietic-cell-specific NPF activated downstream of TCR, originally identified as a target of loss-of-function mutations in the X-linked immunodeficiency Wiskott-Aldrich syndrome (WAS) (Derry et al., 1994; Machesky and Insall, 1998; Takenawa and Miki, 2001).