Human anti-smallpox long-lived memory B cells are defined by dynamic interactions in the splenic niche and long-lasting germinal center imprinting.

Memory B cells (MBCs) can persist for a lifetime, but the mechanisms that allow their long-term survival remain poorly understood. Here, we isolated and analyzed human splenic smallpox/vaccinia protein B5-specific MBCs in individuals who were vaccinated more than 40 years ago. Only a handful of clones persisted over such an extended period, and they displayed limited intra-clonal diversity with signs of extensive affinity-based selection. These long-lived MBCs appeared enriched in a CD21hiCD20hi IgG+ splenic B cell subset displaying a marginal-zone-like NOTCH/MYC-driven signature, but they did not harbor a unique longevity-associated transcriptional or metabolic profile. Finally, the telomeres of B5-specific, long-lived MBCs were longer than those in patient-paired naive B cells in all the samples analyzed. Overall, these results imply that separate mechanisms such as early telomere elongation, affinity selection during the contraction phase, and access to a specific niche contribute to ensuring the functional longevity of MBCs.

TSC-22 Promotes Interleukin-2-Deprivation Induced Apoptosis in T-Lymphocytes.

Originally described as a TGF-ß-inducible gene, tsc-22 (Transforming growth factor-beta Stimulated Clone 22) encodes a transcriptional regulator affecting biological processes such as cell growth, differentiation, or apoptosis. Along with GILZ (Glucocorticoid-Induced Leucine Zipper), TSC-22 belongs to the evolutionary conserved TSC-22 Domain family. We previously showed that, in T-lymphocytes, GILZ expression was induced upon IL-2 withdrawal, delaying apoptosis through down-regulation of the pro-apoptotic protein BIM expression. The aim of this work was then to elucidate the respective roles of GILZ and TSC-22 upon IL-2 deprivation-induced apoptosis. We report here that these two highly homologous genes are concomitantly expressed in most human tissues and in primary T-lymphocytes and that expression of TSC-22 promotes T-lymphocytes apoptosis by inhibiting GILZ functions. Indeed, we demonstrated that TSC-22 expression in the murine lymphoid CTLL-2 cell line promoted IL-2 deprivation-induced apoptosis. BIM expression and caspases-9 and -3 activities were markedly increased in TSC-22 expressing clones compared to control clones. Analysis of GILZ expression revealed that TSC-22 prevented the induction of the GILZ protein upon IL-2 deprivation, by inhibiting gilz mRNA transcription. These results suggested that TSC-22 could counteract the protective effect of GILZ on IL-2-deprivation-induced apoptosis. Moreover, TSC-22-induced inhibition of GILZ expression was also found in CTLL-2 cells treated with glucocorticoids or TGF-ß. In the human NKL cell line deprived of IL-2, TSC-22 showed the same effect and thus may represent a potent repressor of GILZ expression in IL-2-dependent cells, independently of the cell type, or the stimulus, leading to an increase of IL-2-deprived T-cells apoptosis. J. Cell. Biochem. 117: 1855-1868, 2016. © 2016 Wiley Periodicals, Inc.

[TSC-22D proteins: new regulators of cell homeostasis?]. / Les protéines de la famille TSC-22D - De nouveaux régulateurs de l'homéostasie cellulaire ?

The GILZ (glucocorticoid-induced leucine zipper) protein has first been identified as a glucocorticoid-responsive gene and is now presented as a major regulator of inflammation. Expanding literature documents a role for GILZ as a mediator of the immuno-modulatory and anti-inflammatory effects of glucocorticoids, mainly through interference with key signal transduction pathways such as nuclear factor-kappa B (NF-kB) or activated protein-1 (AP-1). The TSC-22 (TGF-ß-stimulated clone-22) protein is described as an apoptosis modulator and as a new tumor suppressor gene. GILZ and TSC-22, characterized by the presence of a leucine zipper domain and a TSC-box, belong to the TSC-22D (TSC-22 domain) family of proteins which comprises today 18 members. Functions of these proteins suggest that this family plays a major role in cell homeostasis and in the regulation of the immune system.

Glucocorticoid-Induced Leucine Zipper Is Expressed in Human Neutrophils and Promotes Apoptosis through Mcl-1 Down-Regulation.

Glucocorticoid-induced leucine zipper (GILZ) is a potent anti-inflammatory protein, the expression of which is mainly induced by glucocorticoids (GCs) in haematopoietic cells. GILZ regulates signal transduction pathways of inflammation and plays a role in cell survival. The objective of this study was to evaluate the expression and mechanisms of action of GILZ in the apoptosis of human neutrophils. GILZ expression was induced by GCs in human neutrophils, enhanced upon phosphatidylinositol 3-kinase inhibition and resulted in apoptosis amplification. We then stably transfected PLB-985 cells with the human gilz gene and differentiated both control and GILZ-overexpressing clones in neutrophil-like cells. GILZ overexpression in PLB-985 cells led to an exacerbated apoptosis, associated with caspase-3, caspase-9 and caspase-8 activations, and a loss of mitochondrial potential, suggesting that GILZ-induced apoptosis used the mitochondrial pathway. The expression of BH3 interacting domain death agonist, Bcl-2 interacting mediator of cell death, annexin-A1 and Bcl-2-associated X was not affected in PLB-985-GILZ clones, but phosphorylation and subsequent proteasomal degradation of myeloid cell leukemia-1 (Mcl-1) were observed. Noteworthy, Mcl-1 phosphorylation was related to a significant and sustained activation of c-Jun N-terminal kinase (JNK) in PLB-985-GILZ clones. These results reveal GILZ to be a new actor in apoptosis regulation in neutrophil-like cells involving JNK and Mcl-1.

Neutrophil expression of glucocorticoid-induced leucine zipper (GILZ) anti-inflammatory protein is associated with acute respiratory distress syndrome severity.

BACKGROUND: Glucocorticoid-induced leucine zipper (GILZ) is a potent anti-inflammatory protein involved in neutrophil apoptosis and the resolution of inflammation. Given the numerous pathophysiologic roles of neutrophils in the acute respiratory distress syndrome (ARDS), we postulated that neutrophil GILZ expression might be induced during ARDS, to modulate the inflammatory process and participate in lung repair. METHODS: This single-center, prospective, observational cohort study took place in the surgical intensive care unit of Bichat Hospital (Paris, France) and involved 17 ARDS patients meeting the Berlin criteria at inclusion, and 14 ventilated controls without ARDS. Serial blood samples were obtained every 2 days until extubation or death (from 1 to 9 samples per patient). GILZ protein and gene expression was quantified in blood neutrophils, along with markers of inflammation (CRP, extracellular DNA) or its resolution (Annexin A1). RESULTS: Neutrophil GILZ expression was detected at the transcriptional and/or translational level in 9/17 ARDS patients (in particular 7/10 severe ARDS) and in 2/14 ventilated controls. The highest mRNA levels were observed in the most severely ill patients (p < 0.028). GILZ was expressed in about ¾ of the corticosteroid-treated patients and its expression could also occur independently of corticosteroids, suggesting that inflammatory signals may also induce neutrophil GILZ expression in vivo. CONCLUSIONS: In this pilot study, we show for the first time that blood neutrophils from patients with ARDS can express GILZ, in keeping with an anti-inflammatory and regulatory endogenous role of GILZ in humans. Contrary to some markers of inflammation or its resolution, the levels of gilz gene expression were related to ARDS severity.