A DIAGNOSTIC ASSAY FOR THE WISKOTT-ALDRICH SYNDROME AND ITS VARIANT FORMS

Background: The Wiskott-Aldrich syndrome (WAS) is an X-linked recessiv e disease characterized by severe thrombocytopenia, eczema, and impair ed immunity, While the diagnosis is usually straightforward, the syndr ome may be expressed in an attenuated form, a phenotype which is diffi cult to distinguish from other types of congenital thrombocytopenia. A lthough a molecular-based assay for diagnosis of the spectrum of WAS p atients has not been available, recent data indicate that WAS is assoc iated with a specific profile of impaired mitogen responsiveness and s uggest that detection of this abnormality may provide a diagnostic mar ker for all forms of the disease, To address this issue, we have studi ed patients with classical and atypical WAS for their lymphocyte proli ferative responses to four T cell mitogenic stimuli and compared their response patterns to those detected in unaffected children. Methods: Clinical histories and informed consent were obtained from 23 patients with either classical or putative tie, atypical) WAS, 16 subjects wit h other disorders, and 12 healthy children, Peripheral blood mononucle ar cells (PBMCs) collected from patients and controls were resuspended in culture medium, stimulated with the T cell mitogens phytohemagglut inin (PHA), concanavalin A (Con A), neuraminidase/galactose oxidase (N AGO), or periodate, and cultured for 60 h in 0.2 mt aliquots, Followin g a 20 h pulse with H-3-thymidine, cultures were harvested and the H-3 -thymidine uptake was evaluated by liquid scintillation counting. Resu lts: The most striking observation involved response to periodate. Whi le lymphocytes from all healthy control children proliferated in respo nse to periodate treatment, cells from both classical as well as atypi cal WAS patients consistently failed to proliferate in response to thi s mitogen, By contrast, lymphocyte proliferative responses to PHA, Con A, and NAGO were detected in all patients and controls, although resp onses generally were lower in cells from classical WAS patients compar ed to other children. In two WAS patients, bone marrow transplantation and clinical improvement were associated with a change from no period ate response (pre-transplant) to periodate responsiveness (post-transp lant). In contrast to the WAS patients, cells from patients with other hematologic and primary immune deficiency diseases responded uniforml y to all four mitogens, including periodate. Conclusions: The data pre sented here indicate that T cells from patients with either classical or attenuated WAS fail to undergo proliferation in response to perioda te, an agent that induced extensive T cell mitogenesis of cells from a ll healthy controls as well as patients with diseases other than WAS, As the WAS patients' cells did proliferate in response to treatment wi th other T cell mitogens, it appears that periodate induced T cell pro liferation is selectively impaired in WAS and that detection of this d efect may be of value in the distinction of both classical and attenua ted WAS from other thrombocytopenic conditions.