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Heightened mitochondrial priming is the basis for apoptotic hypersensitivity of CD4+ CD8+ thymocytes.

ABSTRACT: It is well established that CD4(+) CD8(+) thymocytes are more sensitive to myriad death stimuli than CD4(+) or CD8(+) single positive (SP) thymocytes. The mechanism behind this hypersensitivity to apoptosis of CD4(+) CD8(+) thymocytes is not understood. To test whether the difference lay in the apoptotic preset of mitochondria, established by the BCL-2 family of proteins, we developed a method, FACS-based BH3 profiling. Using this tool, we could discriminate thymocyte subpopulations and demonstrate that mitochondria in double positive (DP) thymocytes are more primed for death than those in single positive counterparts. Loss of proapoptotic BIM, known to cause autoimmunity, also causes loss of "priming." Priming is a phenotype with physiologic consequences, which can be measured at the single-cell level in complex samples using FACS-based BH3 profiling.

SUBMITTER: Ryan JA

PROVIDER: S-EPMC2919900 | biostudies-other | 2010 Jul

REPOSITORIES: biostudies-other

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Heightened mitochondrial priming is the basis for apoptotic hypersensitivity of CD4+ CD8+ thymocytes.

Ryan Jeremy A JA Brunelle Joslyn K JK Letai Anthony A

Proceedings of the National Academy of Sciences of the United States of America 20100706 29

It is well established that CD4(+) CD8(+) thymocytes are more sensitive to myriad death stimuli than CD4(+) or CD8(+) single positive (SP) thymocytes. The mechanism behind this hypersensitivity to apoptosis of CD4(+) CD8(+) thymocytes is not understood. To test whether the difference lay in the apoptotic preset of mitochondria, established by the BCL-2 family of proteins, we developed a method, FACS-based BH3 profiling. Using this tool, we could discriminate thymocyte subpopulations and demonstr ...[more]

PMID: 20615979

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Project description:The outcome of untreated HIV-1 infection is progression to AIDS and death in nearly all cases. Some important exceptions are the small number of patients infected with HIV-1 deleted for the accessory gene, nef. With these infections, disease progression is entirely suppressed or greatly delayed. Whether Nef is critical for high levels of replication or is directly cytotoxic remains controversial. The major problem in determining the role of Nef in HIV/AIDS has been the lack of tractable in vivo models where Nef's complex pathogenic phenotype can be recapitulated.Intravenous inoculation (3000 to 600,000 TCIU) of BLT humanized mice with HIV-1LAI reproducibly establishes a systemic infection. HIV-1LAI (LAI) replicates to high levels (peak viral load in blood 8,200,000?±?1,800,000 copies of viral RNA/ml, range 3,600,000 to 20,400,000; n?=?9) and exhaustively depletes CD4+ T cells in blood and tissues. CD4+CD8+ thymocytes were also efficiently depleted but CD4+CD8- thymocytes were partially resistant to cell killing by LAI. Infection with a nef-deleted LAI (LAINefdd) gave lower peak viral loads (1,220,000?±?330,000, range 27,000 to 4,240,000; n?=?17). For fourteen of seventeen LAINefdd-infected mice, there was little to no loss of either CD4+ T cells or thymocytes. Both LAI- and LAINefdd-infected mice had about 8% of total peripheral blood CD8+ T cells that were CD38+HLA-DR+ compared <1% for uninfected mice. Three exceptional LAINefdd-infected mice that lost CD4+ T cells received 600,000 TCIU. All three exhibited peak viral loads over 3,000,000 copies of LAINefdd RNA/ml. Over an extended time course, substantial systemic CD4+ T cell loss was observed for the three mice, but there was no loss of CD4+CD8+ or CD4+CD8- thymocytes.We conclude Nef is necessary for elevated viral replication and as a result indirectly contributes to CD4+ T cell killing. Further, Nef was not necessary for the activation of peripheral blood CD8+ T cells following infection. However, CD4+CD8+ thymocyte killing was dependent on Nef even in cases of elevated LAINefdd replication and T cell loss. This depletion of thymic T cell precursors may be a significant factor in the elevated pathogenicity of CXCR4 trophic HIV-1.

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Dataset Information

Heightened mitochondrial priming is the basis for apoptotic hypersensitivity of CD4+ CD8+ thymocytes.

Publications

Heightened mitochondrial priming is the basis for apoptotic hypersensitivity of CD4+ CD8+ thymocytes.

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