WAS and Wiskott-Aldrich syndrome: While thymic T cell development appears to be relatively normal in WAS KO mice (Cotta-de-Almeida et al. 2007; Snapper et al. 1998; Zhang et al. 1999), reduced number of circulating T cells are found in WAS KO mice (Snapper et al. 1998) as well as WAS patients (Ochs et al. 1980; Park et al. 2004).