c-Rel-dependent priming of naive T cells by inflammatory cytokines

CD38 is required for priming by TNF-alpha: a mechanism for extracellular coordination of cell fate

Cytokines are protein messengers that act to modulate the differentiation or activation of their target cells. Bone marrow macrophages can become activated tissue macrophages, dendritic cells, or osteoclasts depending on to which cytokines they are exposed. However, one cytokine can often induce divergent outcomes, suggesting that other signals are needed to establish the specificity of the result. We hypothesize that these signals may derive from the local environment and serve to prime cells to respond toward a specific outcome. Here, it is shown that the cytokine TNF-alpha is capable of affecting the fate of macrophages by upregulating the NADase CD38. CD38 upregulation primes macrophages, such that signals induced by inflammatory stimuli are augmented, while those leading to osteoclast formation are inhibited. We show that TNF-alpha-induced CD38 expression negatively affects the expression of osteoclast markers, while it enhances inflammatory gene expression by decreasing ERK1/2 phosphorylation and increasing NF-kappaB activation. Furthermore, it is shown that CD38 may reduce osteoclastogenesis and increase inflammatory gene induction by decreasing cellular histone deacetylase activity. These results provide a demonstration of how a cytokine can prime cells to differentiate toward a certain lineage or acquire enhanced activation characteristics. Since CD38 is an ectoenzyme, we suggest that the modulation of extracellular NAD(+) metabolism likely serves as a unique mechanism to coordinate the fate of cells within a local environment.

NF-kappaB and the immune response

One of the primary physiological roles of nuclear factor-kappa B (NF-kappaB) is in the immune system. In particular, NF-kappaB family members control the transcription of cytokines and antimicrobial effectors as well as genes that regulate cellular differentiation, survival and proliferation, thereby regulating various aspects of innate and adaptive immune responses. In addition, NF-kappaB also contributes to the development and survival of the cells and tissues that carry out immune responses in mammals. This review, therefore, describes the role of the NF-kappaB pathway in the development and functioning of the immune system.

Unravelling the complexities of the NF-κB signalling pathway using mouse knockout and transgenic models

The nuclear factor-kappaB (NF-kappaB) signalling pathway serves a crucial role in regulating the transcriptional responses of physiological processes that include cell division, cell survival, differentiation, immunity and inflammation. Here we outline studies using mouse models in which the core components of the NF-kappaB pathway, namely the IkappaB kinase subunits (IKKalpha, IKKbeta and NEMO), the IkappaB proteins (IkappaBalpha, IkappaBbeta, IkappaBvarepsilon and Bcl-3) and the five NF-kappaB transcription factors (NF-kappaB1, NF-kappaB2, c-Rel, RelA and RelB), have been genetically manipulated using transgenic and knockout technology.

Numbers and activities of CD56+ T cells and natural killer cells in cirrhotic livers with hepatitis C

AIM: To study the numbers and anti-tumor activities of CD56⁺ T cells and natural killer (NK) cells in cirrhotic liver with hepatitis C (HC).

METHODS: Hepatic mononuclear cells (MNC) were isolated from liver specimens obtained from the patients (n = 16) with HC-induced cirrhosis by liver biopsy. In addition, the numbers of CD56⁺ T cells and natural killer cells were determined by flow cytometry. Liver MNC and peripheral blood mononuclear cells (PBMC) were co-cultured with the interleukin-2 (IL-2), respectively, and the production of interferon-g (IFN-g) and the antitumor activity were measured.

RESULTS: The percentages of CD56⁺ T cells among hepatic MNC in health individuals, HC and HC-induced cirrhosis patients were 20.4% ± 6.2%, 11.2% ± 3.1% and 5.0% ± 1.6%, respectively; the proportions of NK cells among liver MNC in the three groups were 31.1% ± 9.7%, 31.6% ± 8.3% and 18.3% ± 5.4%, respectively; the productions of IFN-g in the three groups were 7.4 ± 2.4, 3.2 ± 1.8 and 1.9 ± 0.5 mg/L, respectively; the anti-tumor activities hepatic MNC in the three groups were 61.1% ± 17.1%, 59.2% ± 14.6%, and 26.7% ± 8.5%, respectively. For the above four groups of parameters, the changes in HC-induced cirrhosis patients was the most significant (P < 0.05).

CONCLUSION: The numbers and anti-tumor activities of CD56⁺T cells and NK cells are decreased in cirrhotic livers with HC.

CD4+ T-cell memory: generation and multi-faceted roles for CD4+ T cells in protective immunity to influenza

We have outlined the carefully orchestrated process of CD4+ T-cell differentiation from naïve to effector and from effector to memory cells with a focus on how these processes can be studied in vivo in responses to pathogen infection. We emphasize that the regulatory factors that determine the quality and quantity of the effector and memory cells generated include (i) the antigen dose during the initial T-cell interaction with antigen-presenting cells; (ii) the dose and duration of repeated interactions; and (iii) the milieu of inflammatory and growth cytokines that responding CD4+ T cells encounter. We suggest that heterogeneity in these regulatory factors leads to the generation of a spectrum of effectors with different functional attributes. Furthermore, we suggest that it is the presence of effectors at different stages along a pathway of progressive linear differentiation that leads to a related spectrum of memory cells. Our studies particularly highlight the multifaceted roles of CD4+ effector and memory T cells in protective responses to influenza infection and support the concept that efficient priming of CD4+ T cells that react to shared influenza proteins could contribute greatly to vaccine strategies for influenza.

Nuclear factor-kappaB dimer exchange promotes a p21(waf1/cip1) superinduction response in human T leukemic cells

The nuclear factor-kappaB (NF-kappaB)/Rel transcription factors are recognized as critical apoptosis regulators. We reported previously that NF-kappaB contributes to chemoresistance of CEM human T leukemic cells in part through its ability to induce p21(waf1/cip1). Here, we provide evidence that sequential NF-kappaB-activating signals induce heightened NF-kappaB DNA binding and p21(waf1/cip1) induction in CEM and additional T leukemic cell lines. This response arises from exceedingly low basal expression of the p105/p50 NF-kappaB subunit encoded by the NFKB1 gene in these cell lines. An initial NF-kappaB activation event enhances the recruitment of p65 and ELF1 to the NFKB1 promoter, leading to p65- and ELF1-dependent synthesis of p105/p50, which promotes an exchange of NF-kappaB complexes to p50-containing complexes with an increased DNA-binding activity to certain NF-kappaB target elements. Subsequent stimulation of these cells with an anticancer agent, etoposide, results in augmented NF-kappaB-dependent p21(waf1/cip1) induction and increased chemoresistance of the leukemia cells. Thus, we propose that low basal NFKB1 expression coupled with sequential NF-kappaB activation events can promote increased chemoresistance in certain T leukemic cells.

IL-1beta, but not IL-1alpha, is required for antigen-specific T cell activation and the induction of local inflammation in the delayed-type hypersensitivity responses

As IL-1 expression is augmented in delayed-type hypersensitivity (DTH) responses, we analyzed the role of IL-1 in this response. DTH responses against methyl BSA (mBSA) were significantly suppressed in IL-1beta-deficient (IL-1beta-/-) and IL-1alpha/beta-/- mice, but not in IL-1alpha-/- mice. In contrast, responses in IL-1R antagonist-/- (IL-1Ra-/-) mice were exacerbated. Lymph node cells derived from mBSA-sensitized IL-1beta-/-, IL-1alpha/beta-/- and IL-1R type I (IL-1RI)-/- mice, but not from IL-1alpha-/- mice, exhibited reduced proliferative responses against mBSA, while these from IL-1Ra-/- mice demonstrated augmented responses. DTH responses in wild-type mice following adoptive transfer of CD4+ T cells from mBSA-sensitized IL-1alpha/beta-/- mice were also reduced, while those in mice given cells derived from IL-Ra-/- mice were increased. DTH responses in IL-1RI-/-, but not IL-1alpha/beta-/-, mice were reduced upon transplantation of mBSA-sensitized CD4+ T cells from wild-type mice. The recall response of mBSA-sensitized CD4+ T cells against mBSA decreased upon co-culture with dendritic cells (DCs) from IL-1RI-/- mice, while the responses were normal with DCs from IL-1alpha/beta-/- mice. DTH responses in tumor necrosis factor alpha-/- (TNF-/-) mice were also suppressed; the magnitude of the suppression in IL-1alpha/beta-/-TNF-/- mice, however, was similar to that observed in IL-1alpha/beta-/- mice. These observations indicate that IL-1 possesses dual functions during the DTH response. IL-1beta is necessary for the efficient priming of T cells. In addition, CD4+ T cell-derived IL-1 plays an important role in the activation of DCs during the elicitation phase, resulting in the production of TNF, that activate allergen-specific T cells.