International Immunology, Vol. 12, No. 6, 927-935,
June 2000
© 2000 Japanese Society for Immunology
Membrane and transmembrane signaling in Herpesvirus saimiri-transformed human CD4+ and CD8+ T lymphocytes is ATM-independent.
Inmunología, Facultad de Medicina, Universidad Complutense, 28040 Madrid, Spain
1 Inmunología, Hospital Nacional de Niños, San José, Costa Rica
2 Department of Pathology, University of California at Los Angeles School of Medicine, Los Angeles, CA 90095-1732, USA
Correspondence to: J. R. Regueiro
In the genetic disorder ataxia telangiectasia (AT), humoral (B) and cellular (T) immunological abnormalities are frequently observed. As a consequence, AT patients are predisposed to life-threatening sinopulmonary infections. The pathogenic mechanisms remain unknown, but a role for ATM in signal transduction from membrane receptors has been proposed. We have explored the effects of a defective ATMgene on isolated human T-lineage cells from 13 AT patients with proven T cell dysfunction by transforming their CD4+ and CD8+ T lymphocytes with Herpesvirus saimiri, and analyzing their signaling behavior as compared to normal controls. Several functional parameters were assayed in response to both membrane (anti-CD3 and IL-2) and transmembrane (phorbol myristate acetate plus the calcium ionophore ionomycin) stimuli: (i) calcium mobilization, (ii) induction of activation molecules (CD25, CD40 ligand, CD69 and CD71), (iii) cytokine synthesis (IL-2 and tumor necrosis factor-
) and (iv) proliferation. All these early and late activation events were found to be normal in the transformed ATM/T cells, indicating that ATM is not necessary for their induction. As expected, ATM/ transformed T cells showed an increased radiosensitivity by both radioresistant DNA synthesis and cell survival assays. In contrast to an earlier report testing transformed B lymphocytes, our results indicate that transformed mature peripheral T lymphocytes from AT patients do not have intrinsic immune function defects. Rather, the described T-lineage signaling impairments observed in patients may be secondary in vivo to extrinsic ATM-dependent suppressive factors and/or to a developmental defect. These transformed T cells may help to understand the distinct biological role of ATM in different cell types and to develop rational therapies for the immunological dysfunction of AT patients.
Keywords: ATM protein, ataxia telangiectasia, Herpesvirus saimiri-transformed human T cells, T cell signaling
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