The active form of vitamin D (calcitriol) promotes CXCR5 expression during follicular helper T cell differentiation.

Follicular helper T (Tfh) cells promote B cell differentiation and antibody production in the B cell follicles of secondary lymphoid organs. Tfh cells express their signature transcription factor BCL6, interleukin (IL)-21, and surface molecules including inducible T cell costimulator, programmed cell death-1 (PD-1), and the chemokine receptor CXCR5. Migration of Tfh cells to B cell follicles largely depends on the CXCR5 expression induced by interactions with antigen-presenting dendritic cells in the T cell area. How Tfh cells acquire sufficient levels of CXCR5 expression, however, has remained unclear. Using our in vitro culture system to generate CXCR5low Tfh-like cells from naïve CD4+ T cells with IL-6 in the absence of other cell types, we found that the active form of vitamin D, calcitriol, markedly enhanced CXCR5 expression after the release from persistent T cell receptor (TCR) stimulation. CH-223191, an aryl hydrocarbon receptor antagonist, further enhanced CXCR5 expression. IL-12 but not IL-4, in place of IL-6, also supported calcitriol to enhance CXCR5 expression even before the release from TCR stimulation, whereas the cell viability sharply decreased after the release. The Tfh-like cells generated with IL-6 and calcitriol exhibited chemotaxis towards CXCL13, expressed IL-21, and helped B cells to produce IgG antibodies in vitro more efficiently than Tfh-like cells generated without added calcitriol. Calcitriol injections into antigen-primed mice increased the proportion of CXCR5+PD-1+CD4+ cells in their lymphoid organs, and enhanced T cell entry into B-cell follicles. These results suggest that calcitriol promotes CXCR5 expression in developing Tfh cells and regulates their functional differentiation.

Release from persistent T cell receptor engagement and blockade of aryl hydrocarbon receptor activity enhance IL-6-dependent mouse follicular helper T-like cell differentiation in vitro.

Follicular helper T (Tfh) cells are crucial for humoral immunity. Dysregulation of Tfh cell differentiation can cause infectious, allergic, and autoimmune diseases. To elucidate the molecular mechanisms underlying Tfh cell differentiation, we attempted to establish an in vitro mouse model of Tfh cell differentiation in the absence of other cell types. Various cytokines and cell surface molecules are suggested to contribute to the differentiation. We found that stimulating naïve CD4+ T cells with immobilized antibodies to CD3, ICOS, and LFA-1 in the presence of soluble anti-CD28 antibody, IL-6, and antibodies that block IL-2 signaling for 3 days induced the expression of Bcl6 and Rorc(γt), master regulator genes of Tfh and Th17 cells, respectively. TGF-ß significantly enhanced cell proliferation and Bcl6 and Rorc(γt) expression. An additional 2 days of culture without immobilized antibodies selectively downregulated Rorc(γt) expression. These cells produced IL-21 and promoted B cells to produce IgG antibodies. Adding the aryl hydrocarbon receptor (AhR) antagonist CH-223191 to the T cell culture further downregulated Rorc(γt) expression without significantly affecting Bcl6 expression, and upregulated expression of a key Tfh marker, CXCR5. Although their CXCR5 expression levels were still not high, the CH-223191-treated cells showed chemotactic activity towards the CXCR5 ligand CXCL13. On the other hand, AhR agonists upregulated Rorc(γt) expression and downregulated CXCR5 expression. These findings suggest that AhR activity and the duration of T cell receptor stimulation contribute to regulating the balance between Tfh and Th17 cell differentiation. Although this in vitro system needs to be further improved, it may be useful for elucidating the mechanisms of Tfh cell differentiation as well as for screening physiological or pharmacological factors that affect Tfh cell differentiation including CXCR5 expression.

Resolution of Infliximab-Refractory Nivolumab-Induced Acute Severe Enterocolitis After Cyclosporine Treatment in a Patient with Non-Small Cell Lung Cancer.

BACKGROUND Enterocolitis is an immune-related adverse event associated with nivolumab treatment. Although intravenous corticosteroids and infliximab are recommended as a first-line and second-line therapy, respectively, there is no established treatment for severe enterocolitis that is refractory to these drugs. CASE REPORT A 62-year-old male with non-small cell lung cancer, with multiple brain metastasis, received nivolumab as the eighth-line chemotherapy for his disease. A few days after nivolumab administration, grade 2-3 enterocolitis developed in the patient. The enterocolitis improved to grade 1 after careful observation; however, it was aggravated to grade 3 after resuming nivolumab treatment. After cessation of nivolumab, 3.3 mg of intravenous dexamethasone and 40 mg of methylprednisolone were administered for 16 days and subsequently 30-60 mg of oral prednisolone was administered for 50 days, with little improvement in the patient's colitis. A second-line treatment with 5 mg/kg of infliximab was twice attempted, but the patient had persistent diarrhea. Therefore, 50 mg of oral cyclosporine was started as a third-line therapy. Three days after the start of cyclosporine, the number of diarrhea events decreased, with resolution 2 weeks after cyclosporine administration. CONCLUSIONS Oral cyclosporine treatment can be a third-line therapy for enterocolitis associated with immune-related adverse events.

A Molecular and Serological Survey of Rickettsiales Bacteria in Wild Sika Deer (Cervus nippon nippon) in Shizuoka Prefecture, Japan: High Prevalence of Anaplasma Species.

We surveyed Rickettsiales bacteria, including Rickettsia, Ehrlichia, Anaplasma, and Neoehrlichia, in wild sika deer (Cervus nippon nippon) from Shizuoka prefecture, Japan. In spleen samples from 187 deer, Anaplasma phagocytophilum (deer type), A. bovis, and A. centrale were successfully detected by PCR assay targeting to 16S rDNA or p44/msp2, and their positive rates were 96.3% (180/187), 53.5% (100/187), and 78.1% (146/187), respectively. Additionally, 2 or 3 Anaplasma species could be detected from a single deer in 165 spleen samples (88.2%), indicating dual or triple infection. In contrast, A. phagocytophilum (human type) 16S rDNA, Rickettsia gltA, Ehrlichia p28/omp-1, and Neoehrlichia 16S rDNA could not be amplified. The serological test of 105 deer serum samples by immunofluorescence assay showed that the detection of antibodies against antigens of A. phagocytophilum HZ (US-human isolate) and Rickettsia japonica YH were 29.5% (31/105) and 75.2% (79/105), respectively. These findings suggest that A. phagocytophilum (deer type), A. centrale, and A. bovis are highly dominant and prevalent in wild sika deer from Shizuoka, a central region of Japan, and that the antibodies against some Rickettsiales bacteria have also been retained in deer blood.