Successful treatment of relapsing polychondritis with circumferential bronchial wall thickening including the tracheomembranous area with tumor necrosis factor-α inhibitor.

This is a case of a 55-year-old man who presented with cough and anterior chest pain. Tracheal biopsy confirmed the diagnosis of relapsing polychondritis (RP). Although the patient had circumferential bronchial wall thickening extending to the tracheomembranous area and was positive foRPR3-ANCA, he did not meet the diagnostic criteria for granulomatosis with polyangiitis. The patient was refractory to prednisolone + methotrexate + azathioprine and responded to adalimumab, a biologic tumor necrosis factor-α inhibitor effective in RP refractory cases. Herein, we report a rare case of RP with circumferential bronchial wall thickening extending to the tracheomembranous area.

Human PD-1hiCD8+ T Cells Are a Cellular Source of IL-21 in Rheumatoid Arthritis.

Background: Rheumatoid arthritis (RA) is a prototypical autoantibody-driven autoimmune disease in which T-B interactions play a critical role. Recent comprehensive analysis suggests that PD-1+CD8+ T cells as well as two distinct IL-21-producing PD-1+CD4+ T cell subsets, follicular helper T (Tfh) and peripheral helper T (Tph) cells, are involved in the pathogenesis of RA. Herein, we aimed to clarify a generation mechanism of IL-21-producing CD8+ T cells in humans, and to characterize this novel subset in patients with RA. Methods: CD8+ T cells in the peripheral blood (PB) and synovial fluid (SF) of healthy control (HC) and patients with RA were subject to the analysis of IL-21 mRNA and protein. We evaluated the surface marker, cytokine and transcription profiles of IL-21-producing CD8+ T cells in HCPB, RAPB and RASF. Results: IL-21-producing CD8+ T cells were enriched in the CD45RA-(memory) PD-1+, especially PD-1hi subpopulation, and IL-12 and IL-21 synergistically induced IL-21 production by naïve CD8+ T cells. Memory PD-1hiCD8+ T cells in HCPB facilitated plasmablast differentiation and IgG production in an IL-21-dependent manner. In addition, PD-1hiCD8+ T cells in RASF and RAPB produced large amounts of IL-21 and were characterized by high levels of CD28, ICOS, CD69, HLA-DR, and CCR2 but not CXCR5. Furthermore, PD-1hiCD8+ T cells expressed high levels of transcripts of MAF and PRDM1, a feature observed in Tph cells. Conclusions: Identification of IL-21-producing PD-1hiCD8+ T cells expands our knowledge of T cell subsets with B helper functions in RA. Selective targeting of these subsets could pave an avenue for the development of novel treatment strategies for this disease.

Type 1 helper T cells generate CXCL9/10-producing T-bet+ effector B cells potentially involved in the pathogenesis of rheumatoid arthritis.

Efficacy of B-cell depletion therapy highlights the antibody-independent effector functions of B cells in rheumatoid arthritis (RA). Given type 1 helper T (Th1) cells abundant in synovial fluid (SF) of RA, we have determined whether Th1 cells could generate novel effector B cells. Microarray and qPCR analysis identified CXCL9/10 transcripts as highly expressed genes upon BCR/CD40/IFN-γ stimulation. Activated Th1 cells promoted the generation of CXCL9/10-producing T-bet+ B cells. Expression of CXCL9/10 was most pronounced in CXCR3+ switched memory B cells. Compared with peripheral blood, SFRA enriched highly activated Th1 cells that coexisted with abundant CXCL9/10-producing T-bet+ B cells. Intriguingly, anti-IFN-γ antibody and JAK inhibitors significantly abrogated the generation of CXCL9/10-producing T-bet+ B cells. B cell derived CXCL9/10 significantly facilitated the migration of CD4+ T cells. These findings suggest that Th1 cells generate the novel CXCL9/10-producing T-bet+ effector B cells that could be an ideal pathogenic B cell target for RA therapy.

Crystal structure of a pyridoxal 5'-phosphate-dependent aspartate racemase derived from the bivalve mollusc Scapharca broughtonii.

Aspartate racemase (AspR) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that is responsible for D-aspartate biosynthesis in vivo. To the best of our knowledge, this is the first study to report an X-ray crystal structure of a PLP-dependent AspR, which was resolved at 1.90 Šresolution. The AspR derived from the bivalve mollusc Scapharca broughtonii (SbAspR) is a type II PLP-dependent enzyme that is similar to serine racemase (SR) in that SbAspR catalyzes both racemization and dehydration. Structural comparison of SbAspR and SR shows a similar arrangement of the active-site residues and nucleotide-binding site, but a different orientation of the metal-binding site. Superposition of the structures of SbAspR and of rat SR bound to the inhibitor malonate reveals that Arg140 recognizes the ß-carboxyl group of the substrate aspartate in SbAspR. It is hypothesized that the aromatic proline interaction between the domains, which favours the closed form of SbAspR, influences the arrangement of Arg140 at the active site.