Peritoneal B1 and B2 cells respond differently to LPS and IL-21 stimulation.

Peritoneal B cells can be divided into B1 cells (CD11b+CD19+) and B2 cells (CD11b-CD19+) based on CD11b expression. B1 cells play a crucial role in the innate immune response by producing natural antibodies and cytokines. B2 cells share similar traits with B1 cells, influenced by the peritoneal environment. However, the response of both B1 and B2 cells to the same stimuli in the peritoneum remains uncertain. We isolated peritoneal B1 and B2 cells from mice and assessed differences in Interleukin-10(IL-10) secretion, apoptosis, and surface molecule expression following exposure to LPS and Interleukin-21(IL-21). Our findings indicate that B1 cells are potent IL-10 producers, possessing surface molecules with an IgMhiCD43+CD21low profile, and exhibit a propensity for apoptosis in vitro. Conversely, B2 cells exhibit lower IL-10 production and surface markers characterized as IgMlowCD43-CD21hi, indicative of some resistance to apoptosis. LPS stimulates MAPK phosphorylation in B1 and B2 cells, causing IL-10 production. Furthermore, LPS inhibits peritoneal B2 cell apoptosis by enhancing Bcl-xL expression. Conversely, IL-21 has no impact on IL-10 production in these cells. Nevertheless, impeding STAT3 phosphorylation permits IL-21 to increase IL-10 production in peritoneal B cells. Moreover, IL-21 significantly raises apoptosis levels in these cells, a process independent of STAT3 phosphorylation and possibly linked to reduced Bcl-xL expression. This study elucidates the distinct functional and response profiles of B1 and B2 cells in the peritoneum to stimuli like LPS and IL-21, highlighting their differential roles in immunological responses and B cell diversity.

Virus-mediated inactivation of anti-apoptotic Bcl-2 family members promotes Gasdermin-E-dependent pyroptosis in barrier epithelial cells.

Two sets of innate immune proteins detect pathogens. Pattern recognition receptors (PRRs) bind microbial products, whereas guard proteins detect virulence factor activities by the surveillance of homeostatic processes within cells. While PRRs are well known for their roles in many types of infections, the role of guard proteins in most infectious contexts remains less understood. Here, we demonstrated that inhibition of protein synthesis during viral infection is sensed as a virulence strategy and initiates pyroptosis in human keratinocytes. We identified the BCL-2 family members MCL-1 and BCL-xL as sensors of translation shutdown. Virus- or chemical-induced translation inhibition resulted in MCL-1 depletion and inactivation of BCL-xL, leading to mitochondrial damage, caspase-3-dependent cleavage of gasdermin E, and release of interleukin-1α (IL-1α). Blocking this pathway enhanced virus replication in an organoid model of human skin. Thus, MCL-1 and BCL-xL can act as guard proteins within barrier epithelia and contribute to antiviral defense.

CD28 Agonism Improves Survival in Immunologically Experienced Septic Mice via IL-10 Released by Foxp3+ Regulatory T Cells.

Immune dysregulation during sepsis is mediated by an imbalance of T cell costimulatory and coinhibitory signaling. CD28 is downregulated during sepsis and is significantly altered on memory versus naive T cells. Thus, to study the role of CD28 during sepsis in a more physiologically relevant context, we developed a "memory mouse" model in which animals are subjected to pathogen infections to generate immunologic memory, followed by sepsis induction via cecal ligation and puncture. Using this system, we show that agonistic anti-CD28 treatment resulted in worsened survival in naive septic animals but conferred a significant survival advantage in immunologically experienced septic animals. Mechanistically, this differential response was driven by the ability of CD28 agonism to elicit IL-10 production from regulatory T cells uniquely in memory but not naive mice. Moreover, elevated IL-10 released by activated regulatory T cells in memory mice inhibited sepsis-induced T cell apoptosis via the antiapoptotic protein Bcl-xL. Together, these data demonstrate that immunologic experience is an important parameter that affects sepsis pathophysiology and can fundamentally change the outcome of modulating the CD28 pathway during sepsis. This study suggests that testing therapeutic strategies in immunologically experienced hosts may be one way to increase the physiologic relevance of rodent models in sepsis research.

Development of Conformational Antibodies to Detect Bcl-xL's Amyloid Aggregates in Metal-Induced Apoptotic Neuroblastoma Cells.

Bcl-xL, a member of the Bcl-2 family, is a pro-survival protein involved in apoptosis regulation. We have previously reported the ability of Bcl-xL to form various types of fibers, from native to amyloid conformations. Here, we have mimicked the effect of apoptosis-induced caspase activity on Bcl-xL by limited proteolysis using trypsin. We show that cleaved Bcl-xL (ΔN-Bcl-xL) forms fibers that exhibit the features of amyloid structures (BclxLcf37). Moreover, three monoclonal antibodies (mAbs), produced by mouse immunization and directed against ΔN-Bcl-xL or Bcl-xL fibers, were selected and characterized. Our results show that these mAbs specifically target ΔN-Bcl-xL in amyloid fibers in vitro. Upon metal-stress-induced apoptosis, these mAbs are able to detect the presence of Bcl-xL in amyloid aggregates in neuroblastoma SH-SY5Y cell lines. In conclusion, these specific mAbs directed against amyloidogenic conformations of Bcl-xL constitute promising tools for studying, in vitro and in cellulo, the contribution of Bcl-xL in apoptosis. These mAbs may further help in developing new diagnostics and therapies, considering Bcl-xL as a strategic target for treating brain lesions relevant to stroke and neurodegenerative diseases.

Varicella-Zoster Virus infected human neurons are resistant to apoptosis.

Varicella-zoster virus (VZV) is a pathogenic human herpesvirus that causes varicella (chickenpox) as a primary infection following which it becomes latent in ganglionic neurons. Following viral reactivation many years later VZV causes herpes zoster (shingles) as well as a variety of other neurological syndromes. The molecular mechanisms of the conversion of the virus from a lytic to a latent state in ganglia are not well understood. In order to gain insights into the neuron-virus interaction, we studied virus-induced apoptosis in cultures of both highly pure terminally differentiated human neurons and human fetal lung fibroblasts (HFL). It was found that (a) VZV DNA did not accumulate in infected human neurons; (b) VZV transcripts were present at lower levels at all days studied post-infection in neurons; (c) Western blot analysis showed less VZV IE 63 and very little detectable VZV gE proteins in infected neurons compared with HFL; (d) lower levels of the apoptotic marker cleaved Caspase-3 protein were detected in VZV-infected neurons compared with HFL, and higher levels of the known anti-apoptotic proteins Bcl2, Bcl-XL and also the mitochondrial MT-CO2 protein were found in VZV-infected neurons compared with uninfected cells; and (e) both the MT-CO2 protein and VZV IE 63-encoded protein were detected in infected neurons by dual immunofluorescence. These findings showed that neurons are resistant to VZV-induced apoptosis, which may have relevance to the switching of VZV from a lytic to latent ganglionic neuronal infection.

Bcl-XL: A multifunctional anti-apoptotic protein.

B-cell lymphoma-extra large (Bcl-XL) is one of the anti-apoptotic proteins of the Bcl-2 family that is localized in the mitochondria. Bcl-XL is one of the key regulators of apoptosis that can also regulate other important cellular functions. Bcl-XL is overexpressed in many cancers, and its inhibitors have shown good therapeutic effects. Bcl-XL interacts with Beclin 1, a key factor regulating autophagy. Bcl-XL is essential for the survival of neurons and plays protective roles in neuronal injuries. It can promote the growth of neurons and the correct formation of neural networks, enhance synaptic plasticity, and control neurotoxicity. Bcl-XL can also promote the transport of Ca2+ to mitochondria, increase the production of ATP, and improve metabolic efficiency. In addition, targeting Bcl-XL has shown potential value in autoimmune diseases and aging. In this review, we summarize the functions of Bcl-XL in cancer, autophagy, Ca2+ signaling, neuroprotection, neuronal growth and synaptic plasticity, energy metabolism, immunity, and senescence as revealed by investigations conducted in the past 10 years. Moreover, we list some inhibitors that have been developed based on the functions of Bcl-XL.

Identification of a Bcl-xL homolog from orange-spotted grouper (Epinephelus coioides) involved in SGIV-induced nonapoptotic cell death.

Bcl-2 family proteins play essential roles in modulating immune response and controlling cells' fate. Bcl-xL is one of anti-apoptotic protein in this family. In this study, a new Bcl-xL homolog (EcBcl-xL) was identified and characterized from orange-spotted grouper, Epinephelus coioides. EcBcl-xL encoded a 221 amino acid peptides that shared 86% identity to Larimichthys crocea Bcl-xL protein, contained four conserved BH domains and one transmembrane region. The predicted three-dimensional structure of EcBcl-xL was similar with Homo sapiens Bcl-xL. EcBcl-xL widely expressed in all tested tissues with highest expression in head kidney. Its expression level was significantly up-regulated after SGIV infection in vivo. Furthermore, overexpression of EcBcl-xL could inhibit SGIV-induced nonapoptotic cell death and suppressed viral genes transcriptions in GS cells. Our findings suggested that EcBcl-xL might play a role during virus infection through modulating SGIV-induced nonapoptotic cell death.

RORγt limits the amount of the cytokine receptor γc through the prosurvival factor Bcl-xL in developing thymocytes.

The cytokine receptor subunit γc provides critical signals for T cell survival and differentiation. We investigated the molecular mechanism that controls the cell surface abundance of γc during T cell development in the thymus. We found that the amount of γc was low on CD4+CD8+ double-positive (DP) thymocytes before their positive selection to become mature T cells. The transcription factor RORγt was abundant in immature DP thymocytes, and its loss resulted in an increase in the abundance of surface γc, specifically on preselection DP cells. Rather than directly repressing expression of the gene encoding γc, RORγt acted through the antiapoptotic protein Bcl-xL to reduce the abundance of surface γc, which resulted in decreased cytokine signaling and was associated with inhibition of cell metabolism and mitochondrial biogenesis. Accordingly, overexpression of Bcl-xL in RORγt-deficient thymocytes restored the amount of surface γc to that present on normal preselection DP cells. Together, these data highlight a previously unappreciated role for RORγt and Bcl-xL in limiting γc abundance at the cell surface and reveal a signaling circuit in which survival factors control cytokine signaling by limiting the abundance and surface distribution of a receptor subunit shared by several cytokines.

The lysine deacetylase Sirtuin 1 modulates the localization and function of the Notch1 receptor in regulatory T cells.

The ability to tune cellular functions in response to nutrient availability has important consequences for immune homeostasis. The activity of the receptor Notch in regulatory T (Treg) cells, which suppress the functions of effector T cells, is indispensable for Treg cell survival under conditions of diminished nutrient supply. Anti-apoptotic signaling induced by the Notch1 intracellular domain (NIC) originates from the cytoplasm and is spatially decoupled from the nuclear, largely transcriptional functions of NIC. We showed that Sirtuin 1 (Sirt1), which is an NAD+ (nicotinamide adenine dinucleotide)-dependent lysine deacetylase that inhibits NIC-dependent gene transcription, stabilized NIC proximal to the plasma membrane to promote the survival and function of activated Treg cells. Sirt1 was required for NIC-dependent protection from apoptosis in cell lines but not for the activity of the anti-apoptotic protein Bcl-xL. In addition, a variant NIC protein in which four lysines were mutated to arginines (NIC4KR) retained anti-apoptotic activity, but was not regulated by Sirt1, and reconstituted the functions of nonnuclear NIC in Notch1-deficient Treg cells. Loss of Sirt1 compromised Treg cell survival, resulting in antigen-induced T cell proliferation and inflammation in two mouse models. Thus, the Sirt1-Notch interaction may constitute an important checkpoint that tunes noncanonical Notch1 signaling.

MyD88 Shapes Vaccine Immunity by Extrinsically Regulating Survival of CD4+ T Cells during the Contraction Phase.

Soaring rates of systemic fungal infections worldwide underscore the need for vaccine prevention. An understanding of the elements that promote vaccine immunity is essential. We previously reported that Th17 cells are required for vaccine immunity to the systemic dimorphic fungi of North America, and that Card9 and MyD88 signaling are required for the development of protective Th17 cells. Herein, we investigated where, when and how MyD88 regulates T cell development. We uncovered a novel mechanism in which MyD88 extrinsically regulates the survival of activated T cells during the contraction phase and in the absence of inflammation, but is dispensable for the expansion and differentiation of the cells. The poor survival of activated T cells in Myd88-/- mice is linked to increased caspase3-mediated apoptosis, but not to Fas- or Bim-dependent apoptotic pathways, nor to reduced expression of the anti-apoptotic molecules Bcl-2 or Bcl-xL. Moreover, TLR3, 7, and/or 9, but not TLR2 or 4, also were required extrinsically for MyD88-dependent Th17 cell responses and vaccine immunity. Similar MyD88 requirements governed the survival of virus primed T cells. Our data identify unappreciated new requirements for eliciting adaptive immunity and have implications for designing vaccines.

1,25-Dihydroxy Vitamin D3 Modulates Endometriosis-Related Features of Human Endometriotic Stromal Cells.

PROBLEM: We aimed to evaluate modulatory effects of vitamin D3 on endometriosis-related features of endometriotic stromal cells. METHOD OF STUDY: The effect of vitamin D3 on adhesion, invasion, proliferation, apoptosis, cytokine production, and angiogenesis potential of the eutopic (EuESCs), ectopic (EESCs), and control (CESCs) stromal cells from 25 women with and 20 women without endometriosis was investigated. RESULTS: In all groups, vitamin D3 significantly increased cell adhesion (P = 0.0013-0.042), while decreased invasion (P = 0.026-0.031) and proliferation (P = 0.0013-0.039) of EESCs and EuESCs. Such treatment also resulted in a significant decrease in IL-6 production by EESCs (P = 0.039), but had no significant effect on the IL-8 production. This vitamin also caused significant decrease in Bcl-2 gene expression by EuESCs (P = 0.04) and Bcl-xL by EESCs (P = 0.044-0.009). In addition, vitamin D3 treatment reduced VEGF-A gene expression by EESCs (P = 0.046-0.009). CONCLUSION: Based on substantial favourable in vitro effects of vitamin D3 in endometriosis-related features of human endometriotic stromal cells, further investigations on therapeutic potential of this hormone in endometriosis are warranted.

Eosinophil-specific deletion of IκBα in mice reveals a critical role of NF-κB-induced Bcl-xL for inhibition of apoptosis.

Eosinophils are associated with type 2 immune responses to allergens and helminths. They release various proinflammatory mediators and toxic proteins on activation and are therefore considered proinflammatory effector cells. Eosinophilia is promoted by the cytokines interleukin (IL)-3, IL-5, and granulocyte macrophage-colony-stimulating factor (GM-CSF) and can result from enhanced de novo production or reduced apoptosis. In this study, we show that only IL-5 induces differentiation of eosinophils from bone marrow precursors, whereas IL-5, GM-CSF, and to a lesser extent IL-3 promote survival of mature eosinophils. The receptors for these cytokines use the common ß chain, which serves as the main signaling unit linked to signal transducer and activator of transcription 5, p38 mitogen-activated protein kinase, and nuclear factor (NF)-κB pathways. Inhibition of NF-κB induced apoptosis of in vitro cultured eosinophils. Selective deletion of IκBα in vivo resulted in enhanced expression of Bcl-xL and reduced apoptosis during helminth infection. Retroviral overexpression of Bcl-xL promoted survival, whereas pharmacologic inhibition of Bcl-xL in murine or human eosinophils induced rapid apoptosis. These results suggest that therapeutic strategies targeting Bcl-xL in eosinophils could improve health conditions in allergic inflammatory diseases.

IL-10/Janus kinase/signal transducer and activator of transcription 3 signaling dysregulates Bim expression in autoimmune lymphoproliferative syndrome.

BACKGROUND: Autoimmune lymphoproliferative syndrome (ALPS) is a human disorder of T cell homeostasis caused by mutations that impair FAS-mediated apoptosis. A defining characteristic of ALPS is the expansion of double negative T cells (DNTC). Relatively little is known about how defective FAS-driven cell death and the Bcl-2 apoptotic pathway intersect in ALPS patients. OBJECTIVE: We studied changes in Bcl-2 family member expression in ALPS to determine whether the Bcl-2 pathway might provide a therapeutic target. METHODS: We used flow cytometry to analyze the expression of pro- and anti-apoptotic Bcl-2 family members in T cells from 12 ALPS patients and determined the in vitro sensitivity of ALPS DNTC to the pro-apoptotic BH3 mimetic, ABT-737. RESULTS: The pro-apoptotic molecule, Bim, was significantly elevated in DNTC. Although no general pattern of individual anti-apoptotic Bcl-2 family members emerged, increased expression of Bim was always accompanied by increased expression of at least 1 anti-apoptotic Bcl-2 family member. Strikingly, Bim levels in DNTC correlated significantly with serum IL-10 in ALPS patients, and IL-10 was sufficient to mildly induce Bim in normal and ALPS T cells via a Janus kinase/signal transducer and activator of transcription 3-dependent mechanism. Finally, ABT-737 preferentially killed ALPS DNTC in vitro. CONCLUSION: Combined, these data show that an IL-10/Janus kinase/signal transducer and activator of transcription 3 pathway drives Bim expression in ALPS DNTC, which renders them sensitive to BH3 mimetics, uncovering a potentially novel therapeutic approach to ALPS.

A pathogenic role for ER stress-induced autophagy and ER chaperone GRP78/BiP in T lymphocyte systemic lupus erythematosus.

Abnormal regulation of ER stress and apoptosis has been implicated in autoimmune disorders. Particularly, ER stress-induced autophagy and the role of GRP78, or BiP in T lymphocyte survival and death in SLE are poorly understood. This study investigated the pathogenic roles of ER stress-induced autophagy and GRP78/BiP in apoptosis of T lymphocytes. We compared spontaneous and induced autophagy and apoptosis of T lymphocytes in healthy donors and patients with SLE. The molecular mechanism of altered autophagy and apoptosis was investigated in T lymphocytes transfected with siRNA for beclin 1 and CHOP and T lymphocytes overexpressing GRP78. Decreased autophagy and increased apoptosis in response to TG-induced ER stress were observed in lupus T lymphocytes. GRP78 and ER stress-signaling molecules, such as PERK, p-eIF2α, IRE1, and ATF6 decreased, whereas CHOP levels increased in lupus T cells in response to TG. The levels antiapoptotic molecules, Bcl-2 and Bcl-XL decreased, whereas the proapoptotic molecules, Bax and caspase 6, increased in lupus T cells. The TG-induced ER stress altered autophagy and apoptosis, which in turn, led to abnormal T cell homeostasis with increased apoptotic T cell death. We hypothesize that aberrant autophagy of T lymphocytes as a result of ER stress and decreased GRP78 expression is involved in the pathogenesis of SLE and might serve as important therapeutic targets.

Dendritic cell maturation and survival are differentially regulated by TNFR1 and TNFR2.

The capacity of dendritic cells (DC) to regulate adaptive immunity is controlled by their maturation state and lifespan. Although TNF is a well-known maturation and survival factor for DC, the role of the two TNFR, TNFR1 and TNFR2, in mediating these effects is poorly understood. By using unique TNF variants that selectively signal through TNFR1 and/or TNFR2, we demonstrate differential functions of TNFR in human monocyte-derived and blood CD1c(+) DC. Activation of TNFR1, but not TNFR2, efficiently induced DC maturation, as defined by enhanced expression of cell surface maturation markers (CD83, CD86, and HLA-DR) as well as enhanced T cell stimulatory capacity. In contrast, both TNFR1 and TNFR2 significantly protected DC against cell death, indicating that innate signals can promote DC survival in the absence of DC maturation. We further show differential activation of NF-κB signaling pathways by the TNFR: TNFR1 activated both the p65 and p52 pathways, whereas TNFR2 triggered p52, but not p65, activation. Accordingly, the p65 NF-κB pathway only played a role in the prosurvival effect of TNFR1. However, cell death protection through both TNFR was mediated through the Bcl-2/Bcl-xL pathway. Taken together, our data show that TNFR1, but not TNFR2, signaling induces DC maturation, whereas DC survival can be mediated independently through both TNFR. These data indicate differential but partly overlapping responses through TNFR1 and TNFR2 in both inflammatory and conventional DC, and they demonstrate that DC maturation and DC survival can be regulated through independent signaling pathways.

Bcl-xL regulates CD1d-mediated antigen presentation to NKT cells by altering CD1d trafficking through the endocytic pathway.

NKT cells are a unique subset of T cells that recognize glycolipid Ags presented in the context of CD1d molecules. NKT cells mount strong antitumor responses and are a major focus in developing effective cancer immunotherapy. It is known that CD1d molecules are constantly internalized from the cell surface, recycled through the endocytic compartments, and re-expressed on the cell surface. However, little is known about the regulation of CD1d-mediated Ag processing and presentation in B cell lymphoma. Prosurvival factors of the Bcl-2 family, such as Bcl-xL, are often upregulated in B cell lymphomas and are intimately linked to sphingolipid metabolism, as well as the endocytic compartments. We hypothesized that Bcl-xL can regulate CD1d-mediated Ag presentation to NKT cells. We found that overexpression or induction of Bcl-xL led to increased Ag presentation to NKT cells. Conversely, the inhibition or knockdown of Bcl-xL led to decreased NKT cell activation. Furthermore, knockdown of Bcl-xL resulted in the loss of CD1d trafficking to lysosome-associated membrane protein 1(+) compartments. Rab7, a late endosomal protein, was upregulated and CD1d molecules accumulated in the Rab7(+) late endosomal compartment. These results demonstrate that Bcl-xL regulates CD1d-mediated Ag processing and presentation to NKT cells by altering the late endosomal compartment and changing the intracellular localization of CD1d.

IL-33/ST2 axis promotes mast cell survival via BCLXL.

Mast cells (MC) are potent innate immune cells that accumulate in chronically inflamed tissues. MC express the IL-33 receptor IL-1 receptor-related protein ST2 at high level, and this IL-1 family cytokine both activates MC directly and primes them to respond to other proinflammatory signals. Whether IL-33 and ST2 play a role in MC survival remains to be defined. In skin-derived human MC, we found that IL-33 attenuated MC apoptosis without altering proliferation, an effect mediated principally through the antiapoptotic molecule B-cell lymphoma-X large (BCLXL). Murine MC demonstrated a similar mechanism, dependent entirely on ST2. In line with these observations, St2(-/-) mice exhibited reduced numbers of tissue MC in inflamed arthritic joints, in helminth-infected intestine, and in normal peritoneum. To confirm an MC-intrinsic role for ST2 in vivo, we performed peritoneal transfer of WT and St2(-/-) MC. In St2(-/-) hosts treated with IL-33 and in WT hosts subjected to thioglycollate peritonitis, WT MC displayed a clear survival advantage over coengrafted St2(-/-) MC. IL-33 blockade specifically attenuated this survival advantage, confirming IL-33 as the relevant ST2 ligand mediating MC survival in vivo. Together, these data reveal a cell-intrinsic role for the IL-33/ST2 axis in the regulation of apoptosis in MC, identifying thereby a previously unappreciated pathway supporting expansion of the MC population with inflammation.

Protein phosphatase 6 controls BCR-induced apoptosis of WEHI-231 cells by regulating ubiquitination of Bcl-xL.

Crosslinking BCR in the immature B cell line WEHI-231 causes apoptosis. We found that Bcl-xL was degraded by polyubiquitination upon BCR crosslinking and in this study explored the mechanism that controls the degradation of Bcl-xL. Ser(62) of Bcl-xL was phosphorylated by JNK to trigger polyubiquitination, and this was opposed by serine/threonine protein phosphatase 6 (PP6) that physically associated with Bcl-xL. We show BCR crosslinking decreased PP6 activity to allow Ser(62) phosphorylation of Bcl-xL. CD40 crosslinking rescues BCR-induced apoptosis, and we found PP6 associated with CD40 and PP6 activation in response to CD40. Our data suggest that PP6 activity is regulated to control apoptosis by modulating Ser(62) phosphorylation of Bcl-xL, which results in its polyubiquitination and degradation.

Induction of Bcl-xL-specific cytotoxic T lymphocytes in mice.

The induction of active immunity against tumour-associated antigens to prevent relapse of cancer is a promising approach but has so far shown only low efficacy. This low efficacy may in part be due to clonal escape of tumour cell variants by the downregulation of antigen expression or inflammation-induced dedifferentiation. Identification of novel tumour-associated antigens that at the same time are essential for continued tumour cell survival is thus critical for the development of active cancer vaccinations. At the same time, identification of novel endogenous murine tumour antigens will help improve preclinical development of cancer immunotherapy. The anti-apoptotic protein Bcl-xL has been suggested to be such an essential tumour antigen, but the lack of well-defined murine epitopes have delayed preclinical studies of Bcl-xL-targeting cancer vaccines. Here, we report the identification of two novel murine tumour-associated epitopes TAYQSFEQV and AFFSFGGAL derived from mouse Bcl-xL. Dendritic cell (DC)-based vaccination induced CD8(+) T cells capable of producing IFN-γ upon restimulation with these epitopes. Thus, our data may benefit the design of future immunotherapy strategies by providing a preclinical model for cancer vaccination with an endogenous tumour antigen that can be combined with other cancer treatments.