The formation of a uropod by lymphocytes (hand-mirror cells) represents a morphologic stage of immune activation and motility in lymphocytes. Immune complexes have been previously shown to induce hand-mirror-cell (HMC) formation in human lymphocytes and have been associated with increased number of HMC in acute leukemia. We studied the ability of immune complexes to induce HMC in patients with Wiskott-Aldrich syndrome (WAS), a disease of cellular immune deficiency. Our findings indicate that lymphocytes from patients with WAS adhere to immune complexes but have a defect in their ability to form HMC when compared with normal human lymphocytes. These results support the concept that immune complexes induce HMC formation and that the HMC is related to the normal cellular immune response.