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Apoptosis of activated T cells is critical for the termination of immune responses. Here we show that adjuvant-stimulated dendritic cells secrete cytokines that prime activated T cells for survival and analyze the roles of the NF-[kappa]B regulator Bcl-3 and the proapoptotic Bcl-2 family members Bim and Puma. Bcl-3 overexpression increased survival, and activated bcl-[3.sup.-/-] T cells died abnormally rapidly. Cytokines from adjuvant-stimulated dendritic cells induced Bcl-3, but survival through cytokine priming was Bcl-3-independent. Apoptosis inhibition by Bcl-3 involved blockade of Bim activation, because Bim was overactivated in Bcl-3-deficient cells, and Bcl-3 failed to increase survival of [bim.sup.-/-] T cells. However, adjuvants increased survival also in Bim-deficient T cells. This Bim-independent death pathway is at least in part regulated by Puma, as shown by analysis of [puma.sup.-/-] and [noxa.sup.-/-] T cells. IL-1, IL-7, and IL-15 primed T cells for survival even in the absence of Bim or Puma. Our data define interrelations and a Bim-independent pathway to activated T cell death. adjuvant | apoptosis | Bcl-2-family | survival

There is ample evidence that somatic cell differentiation during development is accompanied by extensive DNA demethylation of specific sites that vary between cell types. Although the mechanism of this process has not yet been elucidated, it is likely to involve the conversion of 5mC to 5hmC by Tet enzymes. We show that a Tet2/Tet3 conditional knockout at early stages of B-cell development largely prevents lineage-specific programmed demethylation events. This lack of demethylation affects the expression of nearby B-cell lineage genes by impairing enhancer activity, thus causing defects in B-cell differentiation and function. Thus, tissue-specific DNA demethylation appears to be necessary for proper somatic cell development in vivo. [ABSTRACT FROM AUTHOR]

Although canonical NF-κB signaling is crucial to generate a normal mature B-cell compartment, its role in the persistence of resting mature B cells is controversial. To resolve this conflict, we ablated NF-κB essential modulator (NEMO) and IκB kinase 2 (IKK2), two essential mediators of the canonical pathway, either early on in B-cell development or specifically in mature B cells. Early ablation severely inhibited the generation of all mature B-cell subsets, but follicular B-cell numbers could be largely rescued by ectopic expression of B-cell lymphoma 2 (Bcl2), despite a persisting block at the transitional stage. Marginal zone (MZ) B and B1 cells were not rescued, indicating a possible role of canonical NF-κB signals beyond the control of cell survival in these subsets. When canonical NF-κB signaling was ablated specifically in mature B cells, the differentiation and/or persistence of MZ B cells was still abrogated, but follicular B-cell numbers were only mildly affected. However, the mutant cells exhibited increased turnover as well as functional deficiencies upon activation, suggesting that canonical NF-κB signals contribute to their long-term persistence and functional fitness. [ABSTRACT FROM AUTHOR]

Apoptosis of activated T cells is critical for the termination of immune responses. Here we show that adjuvant-stimulated dendritic cells secrete cytokines that prime activated T cells for survival and analyze the roles of the NF-κB regulator Bcl-3 and the proapoptotic Bcl-2 family members Bim and Puma. Bcl-3 overexpression increased survival, and activated bcl-3-/- T cells died abnormally rapidly. Cytokines from adjuvant-stimulated dendritic cells induced Bcl-3, but survival through cytokine priming was Bcl-3-independent. Apoptosis inhibition by Bcl-3 involved blockade of Bim activation, because Bim was overactivated in Bcl-3-deficient cells, and Bcl-3 failed to increase survival of bim-/- T cells. However, adjuvants increased survival also in Bim-deficient T cells. This Bim-independent death pathway is at least in part regulated by Puma, as shown by analysis of puma-/- and noxa-/- T cells. IL-1, IL-7, and IL-15 primed T cells for survival even in the absence of Bim or Puma. Our data define interrelations and a Bim-independent pathway to activated T cell death. [ABSTRACT FROM AUTHOR]