Cutting Edge: IL-4, IL-21, and IFN-γ Interact To Govern T-bet and CD11c Expression in TLR-Activated B Cells.

T-bet and CD11c expression in B cells is linked with IgG2c isotype switching, virus-specific immune responses, and humoral autoimmunity. However, the activation requisites and regulatory cues governing T-bet and CD11c expression in B cells remain poorly defined. In this article, we reveal a relationship among TLR engagement, IL-4, IL-21, and IFN-γ that regulates T-bet expression in B cells. We find that IL-21 or IFN-γ directly promote T-bet expression in the context of TLR engagement. Further, IL-4 antagonizes T-bet induction. Finally, IL-21, but not IFN-γ, promotes CD11c expression independent of T-bet. Using influenza virus and Heligmosomoides polygyrus infections, we show that these interactions function in vivo to determine whether T-bet(+) and CD11c(+) B cells are formed. These findings suggest that T-bet(+) B cells seen in health and disease share the common initiating features of TLR-driven activation within this circumscribed cytokine milieu.

Application of exogenous mixture of glutathione and stable isotope labeled glutathione for trapping reactive metabolites in cryopreserved human hepatocytes. Detection of the glutathione conjugates using high resolution accurate mass spectrometry.

Metabolites (including reactive metabolites) of troglitazone were generated by incubation with cryopreserved human hepatocytes and trapped in the presence of an exogenous mixture of unlabeled and stable isotope labeled (SIL: [1,2-(13)C, (15)N]-glycine) glutathione (GSH/SIL-GSH). The incubation samples were analyzed using liquid chromatography-high resolution accurate mass spectrometry (LC-HRAMS) implemented on a LTQ Orbitrap mass spectrometer. The GSH conjugates of the reactive metabolites were detected via a characteristic mono-isotopic pattern (peaks separated by 3.0037u). Analysis of the incubation samples led to detection of a number of previously described GSH conjugates, as well as two novel methylated GSH conjugates, which were partially characterized based on accurate mass measurements and MS/MS data. The addition of exogenous GSH led to an increase in the apparent level of detected GSH conjugates. Kinetic isotopic measurements showed that the rates of incorporation of exogenous GSH are conjugate-specific. In conclusion, this approach, based on the use of a mixture of GSH/SIL-GSH, allows facile capture and detection of reactive metabolites in human hepatocytes. Moreover, the data suggest that routine addition of glutathione to the assay medium may be advisable for experiments with cryopreserved hepatocytes.