CTLs devoid of WASp fail to organize the peripheral actin cluster of the cytolytic synapse rich in the adhesion molecule lymphocyte function associated antigen-1 (LFA-1), and many of the WASp-deficient CTLs show breakage of the dense actin ring symmetry, resulting in delayed target cell killing in vitro and in vivo upon viral infection (37–39). Here, WAS is linked to viral infectious disease.