Fas-Mediated Apoptosis Regulates the Composition of Peripheral αβ T Cell Repertoire by Constitutively Purging Out Double Negative T Cells

BACKGROUND: The Fas pathway is a major regulator of T cell homeostasis, however, the T cell population that is controlled by the Fas pathway in vivo is poorly defined. Although CD4 and CD8 single positive (SP) T cells are the two major T cell subsets in the periphery of wild type mice, the repertoire of mice bearing loss-of-function mutation in either Fas (lpr mice) or Fas ligand (gld mice) is predominated by CD4(-)CD8(-) double negative alphabeta T cells that also express B220 and generally referred to as B220+DN T cells. Despite extensive analysis, the basis of B220+DN T cell lymphoproliferation remains poorly understood. In this study we re-examined the issue of why T cell lymphoproliferation caused by gld mutation is predominated by B220+DN T cells. METHODOLOGY AND PRINCIPAL FINDINGS: We combined the following approaches to study this question: Gene transcript profiling, BrdU labeling, and apoptosis assays. Our results show that B220+DN T cells are proliferating and dying at exceptionally high rates than SP T cells in the steady state. The high proliferation rate is restricted to B220+DN T cells found in the gut epithelium whereas the high apoptosis rate occurred both in the gut epithelium and periphery. However, only in the periphery, apoptosis of B220+DN T cell is Fas-dependent. When the Fas pathway is genetically impaired, apoptosis of peripheral B220+DN T cells was reduced to a baseline level similar to that of SP T cells. Under these conditions of normalized apoptosis, B220+DN T cells progressively accumulate in the periphery, eventually resulting in B220+DN T cell lymphoproliferation. CONCLUSIONS/SIGNIFICANCE: The Fas pathway plays a critical role in regulating the tissue distribution of DN T cells through targeting and elimination of DN T cells from the periphery in the steady state. The results provide new insight into pathogenesis of DN T cell lymphoproliferation

Analysis of single nucleotide polymorphisms in the FAS and CTLA-4 genes of peripheral T-cell lymphomas

Angioimmunoblastic T-cell lymphoma (AILT) represents a subset of T-cell lymphomas but resembles an autoimmune disease in many of its clinical aspects. Despite the phenotype of effector T-cells and high expression of FAS and CTLA-4 receptor molecules, tumor cells fail to undergo apoptosis. We investigated single nucleotide polymorphisms (SNPs) of the FAS and CTLA-4 genes in 94 peripheral T-cell lymphomas. Although allelic frequencies of some FAS SNPs were enriched in AILT cases, none of these occurred at a different frequency compared to healthy individuals. Therefore, SNPs in these genes are not associated with the apoptotic defect and autoimmune phenomena in AILT

Coupling of palmitate to ovalbumin inhibits the induction of oral tolerance

Oral tolerance is a phenomenon that may occur in animals exposed to protein antigens for the first time by the oral route. They become unable to produce immune responses at the levels normally observed when they are immunized parenterally with antigen in the presence of adjuvants. Lipids have been used as adjuvants for both parenteral and oral immunization. In the present study we coupled ovalbumin with palmitate residues by incubating the protein with the N-hydroxysuccinimide palmitate ester and tested the preparation for its ability to induce oral tolerance. This was performed by giving 20 mg of antigen to mice by the oral route 7 days prior to parenteral immunization in the presence of Al(OH)3. Mice were bled one week after receiving a booster that was given 2 weeks after primary immunization. Specific antibodies were detected by ELISA. Despite the fact that the conjugates are as immunogenic as the unmodified protein when parenterally injected in mice, they failed to induce oral tolerance. This discrepancy could be explained by differences in the intestinal absorption of the two forms of the antigen. In fact, when compared to the non-conjugated ovalbumin, a fast and high absorption of the lipid-conjugated form of ovalbumin was observed by "sandwich" ELISA

Joint modeling of additive and non-additive genetic line effects in single field trials

The original publication can be found at www.springerlink.comAbstract A statistical approach is presented for selection of best performing lines for commercial release and best parents for future breeding programs from standard agronomic trials. The method involves the partitioning of the genetic effect of a line into additive and non-additive effects using pedigree based inter-line relationships, in a similar manner to that used in animal breeding. A difference is the ability to estimate non-additive effects. Line performance can be assessed by an overall genetic line effect with greater accuracy than when ignoring pedigree information and the additive effects are predicted breeding values. A generalized definition of heritability is developed to account for the complex models presentedHelena Oakey, Arūnas Verbyla, Wayne Pitchford, Brian Cullis and Haydn Kuche

Cytokine mRNA repertoire of peripheral blood mononuclear cells in Takayasu's arteritis

We have investigated constitutive and phytohaemagglutinin (PHA) + phorbol 12-myristate 13-acetate (PMA)-induced gene expression of tumour necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-2, IL-3, IL-4, IL-10, IL-12 and granulocyte macrophage colony-stimulating factor (GM-CSF) in peripheral blood mononuclear cells (PBMCs) of 10 patients with Takayasu's arteritis (TA) and 10 healthy controls by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). The constitutive mRNA expression of TNF-α (69·0 ± 4·0% versus 27·5 ± 18·0%; P = 0·001) and IL-4 (60·0 ± 10·0% versus 0%; P = 0·001) was significantly higher in patients than controls; that of IL-3 was comparable in both groups (38·0 ± 6·0% versus 32·0 ± 5·0%; P = 0·651) while no constitutive mRNA expression was observed for the other cytokines studied. The stimulated PBMCs of patients, as compared with the controls, had higher mRNA gene expression of TNF-α (127·0 ± 16·0% versus 54·0 ± 6·0%; P = 0·001), IFN-γ (93·0 ± 13·0% versus 57·0 ± 5·0%; P = 0·032), IL-2 (109·0 ± 13·0% versus 68·0 ± 6·0%; P = 0·015), IL-3 (60·0 ± 8·0% versus 21·2 ± 3·0%; P = 0·045) and IL-4 (68·0 ± 7·0% versus 27·0 ± 7·2%; P = 0·01) The mRNA expression of IL-10 was lower in patients than controls (35·0 ± 8·0% versus 75·0 ± 12·0%; P = 0·022). The GM-CSF mRNA was similar (102·0 ± 6·0% versus 89·0 ± 5·0%; P = 0·475) in both groups. Stimulation of cells with PHA + PMA showed no IL-12 expression but stimulation with lipopolysaccharide induced higher IL-12 mRNA in patients than controls (83·0 ± 14·0% versus 33·0 ± 4·0%; P = 0·005). Our data suggest that an inflammatory cytokine signature exists in TA with a key role for TNF-α, IL-4, IL-10 and IL-12 in different pathological processes of the disease