We evaluated the effects of recombinant DNA IL-2, a T-cell lymphokine which is essential for normal immune function on the responses to mitogen and alloantigen of peripheral blood mononuclear cells (PBMC) from 3 ADA deficient patients. There was significant enhancement by IL-2 of mitogenic responses to phytohemagglutinin (PHA), pokeweed mitogen (PWM) and alloantigen (MLR) in all 3 patients. Patients with ADA positive severe combined immunodeficiency disease showed no responses to IL-2:To determine the responsive cell population we measured T3, T4 and T8 expression in PBMC exposed to PHA ± IL-2. Normal PBMC respond with increased T3 cells but no change in T4 or T8 expression. The ADA deficient PBMC incubated with an ADA inhibitor, deoxyadenosine and PHA cannot be salvaged by IL-2. These results demonstrate a unique feature of the immunodeficiency in ADA deficiency and provide further evidence that purine metabolism is distinct in lymphocyte subsets. Also, the standard in vitro cell model of ADA deficiency may be significantly limited in its use in understanding the pathogenesis of this disease.
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