Soluble flagellin coimmunization attenuates Th1 priming to Salmonella and clearance by modulating dendritic cell activation and cytokine production.

Soluble flagellin (sFliC) from Salmonella Typhimurium (STm) can induce a Th2 response to itself and coadministered antigens through ligation of TLR5. These properties suggest that sFliC could potentially modulate responses to Th1 antigens like live STm if both antigens are given concurrently. After coimmunization of mice with sFliC and STm there was a reduction in Th1 T cells (T-bet(+) IFN-γ(+) CD4 T cells) compared to STm alone and there was impaired clearance of STm. In contrast, there was no significant defect in the early extrafollicular B-cell response to STm. These effects are dependent upon TLR5 and flagellin expression by STm. The mechanism for these effects is not related to IL-4 induced to sFliC but rather to the effects of sFliC coimmunization on DCs. After coimmunization with STm and sFliC, splenic DCs had a lower expression of costimulatory molecules and profoundly altered kinetics of IL-12 and TNFα expression. Ex vivo experiments using in vivo conditioned DCs confirmed the effects of sFliC were due to altered DC function during a critical window in the coordinated interplay between DCs and naïve T cells. This has marked implications for understanding how limits in Th1 priming can be achieved during infection-induced, Th1-mediated inflammation.

Morning vaccination enhances antibody response over afternoon vaccination: A cluster-randomised trial.

OBJECTIVES: Older adults are less able to produce a protective antibody response to vaccinations. One factor that contributes to this is immune ageing. Here we examined whether diurnal variations in immune responses might extend to the antibody response to vaccination. DESIGN: We utilised a cluster-randomised trial design. SETTING: 24 General Practices (GPs) across the West Midlands, UK who were assigned to morning (9-11am; 15 surgeries) or afternoon (3-5pm; 9 surgeries) vaccination times for the annual UK influenza vaccination programme. PARTICIPANTS: 276 adults (aged 65+ years and without a current infection or immune disorder or taking immunosuppressant medication). INTERVENTIONS: Participants were vaccinated in the morning or afternoon between 2011 and 2013. MAIN OUTCOME MEASURES: The primary outcome was the change in antibody titres to the three vaccine influenza strains from pre-vaccination to one month post-vaccination. Secondary outcomes of serum cytokines and steroid hormone concentrations were analysed at baseline to identify relationships with antibody responses. RESULTS: The increase in antibody levels due to vaccination differed between morning and afternoon administration; mean difference (95% CI) for H1N1 A-strain, 293.3 (30.97-555.66) p=.03, B-strain, 15.89 (3.42-28.36) p=.01, but not H3N2 A-strain, 47.0 (-52.43 to 146.46) p=.35; those vaccinated in the morning had a greater antibody response. Cytokines and steroid hormones were not related to antibody responses. No adverse events were reported. CONCLUSIONS: This simple manipulation in the timing of vaccine administration to favour morning vaccination may be beneficial for the influenza antibody response in older adults, with potential implications for vaccination strategies generally. TRIAL REGISTRATION: This trial is registered with the ISRCTN (ISRCTN70898162).

Germinal center dysregulation by histone methyltransferase EZH2 promotes lymphomagenesis.

Protection against deadly pathogens requires the production of high-affinity antibodies by B cells, which are generated in germinal centers (GCs). Alteration of the GC developmental program is common in many B cell malignancies. Identification of regulators of the GC response is crucial to develop targeted therapies for GC B cell dysfunctions, including lymphomas. The histone H3 lysine 27 methyltransferase enhancer of zeste homolog 2 (EZH2) is highly expressed in GC B cells and is often constitutively activated in GC-derived non-Hodgkin lymphomas (NHLs). The function of EZH2 in GC B cells remains largely unknown. Herein, we show that Ezh2 inactivation in mouse GC B cells caused profound impairment of GC responses, memory B cell formation, and humoral immunity. EZH2 protected GC B cells against activation-induced cytidine deaminase (AID) mutagenesis, facilitated cell cycle progression, and silenced plasma cell determinant and tumor suppressor B-lymphocyte-induced maturation protein 1 (BLIMP1). EZH2 inhibition in NHL cells induced BLIMP1, which impaired tumor growth. In conclusion, EZH2 sustains AID function and prevents terminal differentiation of GC B cells, which allows antibody diversification and affinity maturation. Dysregulation of the GC reaction by constitutively active EZH2 facilitates lymphomagenesis and identifies EZH2 as a possible therapeutic target in NHL and other GC-derived B cell diseases.

SLC6A4 expression and anti-proliferative responses to serotonin transporter ligands chlomipramine and fluoxetine in primary B-cell malignancies.

B-cell lines of diverse neoplastic origin express the serotonin transporter (SERT/SLC6A4) and growth arrest in response to SERT-ligands, including the antidepressants chlomipramine and fluoxetine. Here we detail SLC6A4 transcript (Q-PCR) and protein (FACS) expression in primary cells from patients with: chronic lymphocytic leukaemia; mantle cell lymphoma; follicular lymphoma; Burkitt's lymphoma; and diffuse large B-cell lymphoma. The ability of the SERT-binding antidepressants to impact the growth of these cells when sustained on CD154-transfected fibroblasts was also determined. The results reveal a broad spectrum of primary B-cell malignancies expressing SLC6A4 with a proportion additionally displaying growth arrest on SERT-ligand exposure.