Theileria parva-transformed T cells show enhanced resistance to Fas/Fas ligand-induced apoptosis

Küenzi, P; Schneider, P; Dobbelaere, Dirk, (2003). Theileria parva-transformed T cells show enhanced resistance to Fas/Fas ligand-induced apoptosis. Journal of immunology, 3(171), pp. 1224-31. Bethesda, Md.: American Association of Immunologists

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Lymphocyte homeostasis is regulated by mechanisms that control lymphocyte proliferation and apoptosis. Activation-induced cell death is mediated by the expression of death ligands and receptors, which, when triggered, activate an apoptotic cascade. Bovine T cells transformed by the intracellular parasite Theileria parva proliferate in an uncontrolled manner and undergo clonal expansion. They constitutively express the death receptor Fas and its ligand, FasL but do not undergo apoptosis. Upon elimination of the parasite from the host cell by treatment with a theilericidal drug, cells become increasingly sensitive to Fas/FasL-induced apoptosis. In normal T cells, the sensitivity to death receptor killing is regulated by specific inhibitor proteins. We found that anti-apoptotic proteins such as cellular (c)-FLIP, which functions as a catalytically inactive form of caspase-8, and X-chromosome-linked inhibitor of apoptosis protein (IAP) as well as c-IAP, which can block downstream executioner caspases, are constitutively expressed in T. parva-transformed T cells. Expression of these proteins is rapidly down-regulated upon parasite elimination. Antiapoptotic proteins of the Bcl-2 family such as Bcl-2 and Bcl-x(L) are also expressed but, in contrast to c-FLIP, c-IAP, and X-chromosome-linked IAP, do not appear to be tightly regulated by the presence of the parasite. Finally, we show that, in contrast to the situation in tumor cells, the phosphoinositide 3-kinase/Akt pathway is not essential for c-FLIP expression. Our findings indicate that by inducing the expression of antiapoptotic proteins, T. parva allows the host cell to escape destruction by homeostatic mechanisms that would normally be activated to limit the continuous expansion of a T cell population.

Item Type:

Journal Article (Original Article)


05 Veterinary Medicine > Department of Clinical Research and Veterinary Public Health (DCR-VPH) > Molecular Pathobiology

UniBE Contributor:

Dobbelaere, Dirk,




American Association of Immunologists




Factscience Import

Date Deposited:

04 Oct 2013 14:44

Last Modified:

30 Jul 2014 14:38

PubMed ID:


Web of Science ID:


URI: (FactScience: 462)

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