IL-6 and APRIL influence the growth, differentiation, and survival of normal and neoplastic Ab-forming cells (AFC). In this study, we identify two subsets of myeloid cells that associate with the AFC and are the main producers of these factors during a T-dependent Ab response to alum-precipitated protein in mouse lymph nodes. First CD11c ؉ CD8␣ ؊ dendritic cells located in the perivascular area of the T zone provide about half of the IL-6 mRNA produced in the node together with significant amounts of APRIL mRNA. The number of these cells increases during the response, at least in part due to local proliferation. The second subset comprises Gr1 ؉ CD11b ؉ F4/80 ؉ monocyte/macrophages. These colonize the medullary cords during the response and are the other main IL-6 mRNA producers and the greatest source of APRIL mRNA. This medullary cord monocyte/macrophage subset results in local increase of APRIL mRNA that mirrors the polarity of CXCL12 expression in the node. The distribution of these myeloid cell subsets correlates with a gradient of AFC maturation assessed by progressive loss of Ki67 as AFC pass from the B cell follicle along the perivascular areas to the medullary cords.

BackgroundAlthough in vitro IL-4 directs CD4 T cells to produce T helper 2 (Th2)-cytokines, these cytokines can be induced in vivo in the absence of IL-4-signalling. Thus, mechanism(s), different from the in vitro pathway for Th2-induction, contribute to in vivo Th2-differentiation. The pathway for in vivo IL-4-independent Th2-differentiation has yet to be characterized.FindingsHelios (ikzf2), a member of the Ikaros transcription regulator family, is expressed in thymocytes and some antigen-matured T cells as well as in regulatory T cells. It has been proposed that Helios is a specific marker for thymus-derived regulatory T cells. Here, we show that mouse ovalbumin-specific CD4 (OTII) cells responding to alum-precipitated ovalbumin (alumOVA) upregulate Th2 features - GATA-3 and IL-4 - as well as Helios mRNA and protein. Helios is also upregulated in follicular helper T (TFh) cells in this response. By contrast, OTII cells responding to the Th1 antigen - live attenuated ovalbumin-expressing Salmonella - upregulate Th1 features - T-bet and IFN-γ - but not Helios. In addition, CD4 T cells induced to produce Th2 cytokines in vitro do not express Helios. The kinetics of Helios mRNA and protein induction mirrors that of GATA-3. The induction of IL-4, IL-13 and CXCR5 by alumOVA requires NF-κB1 and this is also needed for Helios upregulation. Importantly, Helios is induced in Th2 and TFh cells without parallel upregulation of Foxp3. These findings suggested a key role for Helios in Th2 and TFh development in response to alum-protein vaccines. We tested this possibility using Helios-deficient OTII cells and found this deficiency had no discernable impact on Th2 and TFh differentiation in response to alumOVA.ConclusionsHelios is selectively upregulated in CD4 T cells during Th2 and TFh responses to alum-protein vaccines in vivo, but the functional significance of this upregulation remains uncertain.

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Alum-precipitated protein (alum protein) vaccines elicit long-lasting neutralizing antibody responses that prevent bacterial exotoxins and viruses from entering cells. Typically, these vaccines induce CD4 T cells to become T helper 2 (Th2) cells that induce Ig class switching to IgG1. We now report that CD8 T cells also respond to alum proteins, proliferating extensively and producing IFN-γ, a key Th1 cytokine. These findings led us to question whether adoptive transfer of antigen-specific CD8 T cells alters the characteristic CD4 Th2 response to alum proteins and the switching pattern in responding B cells. To this end, WT mice given transgenic ovalbumin (OVA)-specific CD4 (OTII) or CD8 (OTI) T cells, or both, were immunized with alum-precipitated OVA. Cotransfer of antigen-specific CD8 T cells skewed switching patterns in responding B cells from IgG1 to IgG2a and IgG2b. Blocking with anti-IFN-γ antibody largely inhibited this altered B-cell switching pattern. The transcription factor T-bet is required in B cells for IFN-γ-dependent switching to IgG2a. By contrast, we show that this transcription factor is dispensable in B cells both for IFN-γ-induced switching to IgG2b and for inhibition of switching to IgG1. Thus, T-bet dependence identifies distinct transcriptional pathways in B cells that regulate IFN-γ-induced switching to different IgG isotypes.

IntroductionHomeostatic chemokines, including CXCL13, CXCL19/CXCL21, and CXCL12, are essential organizers of lymphoid tissues in steady states. For instance, they govern the compartmentalization between T and B cells. Importantly, they are also involved in the repositioning of these lymphocytes during the different stages of immune responses. The development of protective memory B cells and long-lived AFCs relies in part on changing expression by the responding B cells of the receptors for the chemokines CXCR5, CCR7, and CXCR4, and of the orphan receptor Epstein-Barr virus-induced molecule-2. 1-3 Thus, during the development of T-dependent antibody responses to protein-based antigens, such as alum-precipitated protein vaccines, chemokine-driven movements in lymph nodes (LNs) are sequentially involved in: (1) the cognate interaction of activated B cells with primed CD4 T cells [4][5][6] in the outer T zone, resulting in B-cell proliferation and class-switch recombination (CSR); or (2) the signals that determine whether B blasts differentiate outside follicles into AFCs without going through affinity maturation 1,3 or form germinal center (GC) in follicles. 2 Through CXCR4-and CXCR5-dependent movements, B cells undergo affinity maturation in GC through proliferation, hypermutation of their immunoglobulin (Ig) variable region genes, and selection of high-affinity mutants that emerge as memory B cells or long-lived AFCs. 7,8 The acquisition of CXCR4 by AFC attracts them to CXCL12 produced in bone marrow's long-term survival niches. In these niches, they maintain protective antibody titers over months. 9,10 Alongside the varying expression of CXCR5/CCR7/CXCR4 that modulates B-cell chemotaxis toward homeostatic chemokines, inflammatory conditions can induce IFN-␥-dependent expression of CXCR3 by lymphocytes, including AFCs. This receptor confers responsiveness to CXCL9, CXCL10, and CXCL11, which are produced at high levels in sites of inflammation. 11 This CXCR3-dependent pathway is important for the recruitment of lymphocytes at sites of infection and clearance of pathogens. 12,13 For instance, CXCR3 expression by mouse AFCs is critical for their migration to the CNS during viral encephalomyelitis. Thus, CXCR3-dependent migration of AFCs to the site of infection clears the virus from the CNS, although this is not achieved with systemic release of antibody. 14,15 CXCR3 ϩ AFCs and memory B cells were found at particularly high frequency in peripheral blood of patients with autoimmune diseases mediated by autoantibodies. 16,17 This suggests that selfreactive AFCs may be produced and/or attracted to and sustained in chronic inflammatory niches through a mechanism that involves CXCR3 and its ligands. 18 In mouse models for lupus erythematosus, AFCs are found in inflamed tissues. 19 Knockdown of CXCR3 has shown the importance of this chemokine receptor in the development of the autoimmune disorders, 20 including the production anti-double-stranded DNA IgG1. 21 Despite the importance of CXCR3 induction for antibody producti...

While IL-4 directs CD4 T cells to produce Th2 cytokines (including IL-4, IL-13, IL-5) in vitro it has been shown that production of these cytokines can be induced in vivo in the absence of IL-4/ IL-13/STAT-6 signaling. The present report shows that CD8 as well as CD4 T cells activated through their TCR, in vitro upregulate the Th2-features -IL-4, IL-13, IL-5, and GATA-3. However, in vivo while alum-precipitated antigen strongly and selectively induces these Th2-features in CD4 T cells, CD8 T cells mount a markedly different response to this antigen. This CD8 response is associated with strong proliferation and production of IFN-, but no Th2-features are induced. Alum-protein formulations are widely used in human vaccines and typically induce strong antibody responses characterized by the differentiation of IL-4-producing CD4 T cells and immunoglobulin class switching to IgG1. Nevertheless, the mechanism responsible for CD4 Th2 and follicular helper T cell commitment triggered by these alum-protein vaccines is still poorly understood. Analysis of the in vivo response to alum-precipitated protein shows that while subsets of CD4 T cells strongly upregulate Th2 and follicular helper T cell features including the surface markers OX40, CXCR5, PD-1, IL-17RB and the transcription factor c-Maf, CD8 T cells do not. These discrete differences between responding CD4 and CD8 T cells provide further insight into the differences between Th2 polarization of CD4 T cells directed by IL-4 in vitro and the induction of IL-4 production by CD4 T cells in vivo in response to alum-precipitated protein.

Synthetic retinoid-related molecules, such as N-(4-hydroxyphenyl)retinamide (fenretinide) and 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437) induce apoptosis in a variety of malignant cells. The mechanism(s) of action of these compounds does not appear to involve retinoic acid receptors (RARs) and retinoid X receptors (RXRs), although some investigators disagree with this view. To clarify whether some retinoid-related molecules can induce apoptosis without involving RARs and/or RXRs, we used 4-[3-(1-heptyl-4,4-dimethyl-2-oxo-1,2,3,4-tetrahydroquinolin-6-yl)-3-oxo-E-propenyl] benzoic acid (AGN193198) that neither binds effectively to RARs and RXRs nor transactivates in RAR-and RXR-mediated reporter assays. AGN193198 potently induced apoptosis in prostate, breast, and gastrointestinal carcinoma cells and in leukemia cells. AGN193198 also abolished growth (by 50% at 130 -332 nM) and induced apoptosis in primary cultures established from prostatic carcinoma (13 patients) and gastrointestinal carcinoma (1 patient). Apoptosis was induced rapidly, as indicated by mitochondrial depolarization and DNA fragmentation. Molecular events provoked by AGN193198 included activation of caspase-3, -8, -9, and -10 (by 4 -6 h) and the production of BID/p15 (by 6 h). These findings show that caspase-mediated induction of apoptosis by AGN193198 is RAR/RXR-independent and suggest that this compound may be useful in the treatment of prostate cancer.

Screening of synthetic retinoids for activity against prostate carcinoma cell lines has identified antagonists of retinoic acid receptors (RARs) as potent growth inhibitors (Hammond et al, 2001, Br J Cancer 85, 453 -462). Here we report that 5 days of exposure to a high-affinity pan-RAR antagonist (AGN194310) abolished growth of prostate carcinoma cells from 14 out of 14 patients, with halfmaximal inhibition between 200 and 800 nM. It had similar effects (at B250 nM) on the prostate carcinoma lines LNCaP, DU-145 and PC-3. AGN194310 inhibited the growth of normal prostate epithelium cells less potently, by 50% at B1 mM. The growth of tumour cells was also inhibited more than that of normal cells when RARb together with RARg, but not RARa alone, were antagonised. Treatment of LNCaP cells with AGN194310 arrested them in G1 of cell cycle within 12 h, with an accompanying rise in the level of p21 waf1 . The cells underwent apoptosis within 3 days, as indicated by mitochondrial depolarisation, Annexin V binding and DNA fragmentation. Apoptosis was caspase-independent: caspases were neither cleaved nor activated, and DNA fragmentation was unaffected by the pan-caspase inhibitor Z-VAD-FMK. The ability of AGN 194310 to induce apoptosis of prostate cancer cells and its differential effect on malignant and normal prostate epithelial cells suggests that this compound may be useful in the treatment of prostate cancer.