Defects in the Bcl-2-Regulated Apoptotic Pathway Lead to Preferential Increase of CD25lowFoxp3+ Anergic CD4+ T Cells.
Summary of "Defects in the Bcl-2-Regulated Apoptotic Pathway Lead to Preferential Increase of CD25lowFoxp3+ Anergic CD4+ T Cells."
Defects in the Bcl-2-regulated apoptotic pathway inhibit the deletion of self-reactive T cells. What is unresolved, however, is the nature and fate of such self-reactive T cells escaping deletion. In this study, we report that mice with such defects contained increased numbers of CD25(low)Foxp3(+) cells in the thymus and peripheral lymph tissues. The increased CD25(low)Foxp3(+) population contained a large fraction of cells bearing self-reactive TCRs, evident from a prominent increase in self-superantigen-specific Foxp3(+)Vβ5(+)CD4(+) T cells in BALB/c Bim(-/-) mice compared with control animals. The survival rate of the expanded CD25(low)Foxp3(+) cells was similar to that of CD25(high)Foxp3(+) CD4 T cells in vitro and in vivo. IL-2R stimulation, but not TCR ligation, upregulated CD25 on CD25(low)Foxp3(+)CD4(+) T cells in vitro and in vivo. The expanded CD25(low)Foxp3(+)CD4(+) T cells from Bim(-/-) mice were anergic but also had weaker regulatory function than CD25(high)Foxp3(+) CD4(+) T cells from the same mice. Analysis of Bim(-/-) mice that also lacked Fas showed that the peripheral homeostasis of this expanded population was in part regulated by this death receptor. In conclusion, these results show that self-reactive T cell escapees from thymic deletion in mice defective in the Bcl-2-regulated apoptotic pathway upregulate Foxp3 and become unresponsive upon encountering self-Ag without necessarily gaining potent regulatory function. This clonal functional diversion may help to curtail autoaggressiveness of escaped self-reactive CD4(+) T cells and thereby safeguard immunological tolerance.
Affiliation
Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.
Journal Details
This article was published in the following journal.
Name: Journal of immunology (Baltimore, Md. : 1950)
ISSN: 1550-6606
Pages: 1566-77
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21742968
- DOI: http://dx.doi.org/10.4049/jimmunol.1100027
Medical and Biotech [MESH] Definitions
Bcl-associated Death Protein
A pro-apoptotic protein and member of the Bcl-2 protein family that is regulated by PHOSPHORYLATION. Unphosphorylated Bad protein inhibits the activity of BCL-XL PROTEIN.
Apoptotic Protease-activating Factor 1
A CARD signaling adaptor protein that plays a role in the mitochondria-stimulated apoptosis (APOPTOSIS, INTRINSIC PATHWAY). It binds to CYTOCHROME C in the CYTOSOL to form an APOPTOSOMAL PROTEIN COMPLEX and activates INITIATOR CASPASES such as CASPASE 9.
Lead Poisoning, Nervous System
Injury to the nervous system secondary to exposure to lead compounds. Two distinct clinical patterns occur in children (LEAD POISONING, NERVOUS SYSTEM, CHILDHOOD) and adults (LEAD POISONING, NERVOUS SYSTEM, ADULT). In children, lead poisoning typically produces an encephalopathy. In adults, exposure to toxic levels of lead is associated with a peripheral neuropathy.
Lead Radioisotopes
Unstable isotopes of lead that decay or disintegrate emitting radiation. Pb atoms with atomic weights 194-203, 205, and 209-214 are radioactive lead isotopes.
Map Kinase Signaling System
An intracellular signaling system involving the MAP kinase cascades (three-membered protein kinase cascades). Various upstream activators, which act in response to extracellular stimuli, trigger the cascades by activating the first member of a cascade, MAP KINASE KINASE KINASES; (MAPKKKs). Activated MAPKKKs phosphorylate MITOGEN-ACTIVATED PROTEIN KINASE KINASES which in turn phosphorylate the MITOGEN-ACTIVATED PROTEIN KINASES; (MAPKs). The MAPKs then act on various downstream targets to affect gene expression. In mammals, there are several distinct MAP kinase pathways including the ERK (extracellular signal-regulated kinase) pathway, the SAPK/JNK (stress-activated protein kinase/c-jun kinase) pathway, and the p38 kinase pathway. There is some sharing of components among the pathways depending on which stimulus originates activation of the cascade.
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