Phosphate Transporter Profiles in Murine and Human Thymi Identify Thymocytes at Distinct Stages of Differentiation.

Thymocyte differentiation is dependent on the availability and transport of metabolites in the thymus niche. As expression of metabolite transporters is a rate-limiting step in nutrient utilization, cell surface transporter levels generally reflect the cell's metabolic state. The GLUT1 glucose transporter is upregulated on actively dividing thymocytes, identifying thymocytes with an increased metabolism. However, it is not clear whether transporters of essential elements such as phosphate are modulated during thymocyte differentiation. While PiT1 and PiT2 are both phosphate transporters in the SLC20 family, we show here that they exhibit distinct expression profiles on both murine and human thymocytes. PiT2 expression distinguishes thymocytes with high metabolic activity, identifying immature murine double negative (CD4-CD8-) DN3b and DN4 thymocyte blasts as well as immature single positive (ISP) CD8 thymocytes. Notably, the absence of PiT2 expression on RAG2-deficient thymocytes, blocked at the DN3a stage, strongly suggests that high PiT2 expression is restricted to thymocytes having undergone a productive TCRß rearrangement at the DN3a/DN3b transition. Similarly, in the human thymus, PiT2 was upregulated on early post-ß selection CD4+ISP and TCRαß-CD4hiDP thymocytes co-expressing the CD71 transferrin receptor, a marker of metabolic activity. In marked contrast, expression of the PiT1 phosphate importer was detected on mature CD3+ murine and human thymocytes. Notably, PiT1 expression on CD3+DN thymocytes was identified as a biomarker of an aging thymus, increasing from 8.4 ± 1.5% to 42.4 ± 9.4% by 1 year of age (p < 0.0001). We identified these cells as TCRγδ and, most significantly, NKT, representing 77 ± 9% of PiT1+DN thymocytes by 1 year of age (p < 0.001). Thus, metabolic activity and thymic aging are associated with distinct expression profiles of the PiT1 and PiT2 phosphate transporters.

Intrathymic adeno-associated virus gene transfer rapidly restores thymic function and long-term persistence of gene-corrected T cells.

BACKGROUND: Patients with T-cell immunodeficiencies are generally treated with allogeneic hematopoietic stem cell transplantation, but alternatives are needed for patients without matched donors. An innovative intrathymic gene therapy approach that directly targets the thymus might improve outcomes. OBJECTIVE: We sought to determine the efficacy of intrathymic adeno-associated virus (AAV) serotypes to transduce thymocyte subsets and correct the T-cell immunodeficiency in a zeta-associated protein of 70 kDa (ZAP-70)-deficient murine model. METHODS: AAV serotypes were injected intrathymically into wild-type mice, and gene transfer efficiency was monitored. ZAP-70-/- mice were intrathymically injected with an AAV8 vector harboring the ZAP70 gene. Thymus structure, immunophenotyping, T-cell receptor clonotypes, T-cell function, immune responses to transgenes and autoantibodies, vector copy number, and integration were evaluated. RESULTS: AAV8, AAV9, and AAV10 serotypes all transduced thymocyte subsets after in situ gene transfer, with transduction of up to 5% of cells. Intrathymic injection of an AAV8-ZAP-70 vector into ZAP-70-/- mice resulted in a rapid thymocyte differentiation associated with the development of a thymic medulla. Strikingly, medullary thymic epithelial cells expressing the autoimmune regulator were detected within 10 days of gene transfer, correlating with the presence of functional effector and regulatory T-cell subsets with diverse T-cell receptor clonotypes in the periphery. Although thymocyte reconstitution was transient, gene-corrected peripheral T cells harboring approximately 1 AAV genome per cell persisted for more than 40 weeks, and AAV vector integration was detected. CONCLUSIONS: Intrathymic AAV-transduced progenitors promote a rapid restoration of the thymic architecture, with a single wave of thymopoiesis generating long-term peripheral T-cell function.

High levels of natural killer cells are associated with response to tocilizumab in patients with severe rheumatoid arthritis.

OBJECTIVES: We aimed to assess the effect of tocilizumab (TCZ), an IL-6 receptor inhibitor, on B, T, NK and NKT cells in patients with RA and to study the cell type predictors of remission. We also compared NK cells in patients with RA and in controls. METHODS: RA patients included in the study met the 2010 ACR/European League Against Rheumatism (EULAR) criteria, were receiving stable doses of steroids and had not received rituximab in the previous year. Different B and T cell subsets, NK cells and NKT cells were assessed by flow cytometry along with perforin A and granzyme B to estimate NK cell cytotoxicity. RESULTS: We included 92 RA patients, including 20 requiring TCZ treatment and 15 requiring anti-TNF drugs, and 25 controls. At baseline, the proportion of CD56(dim)CD16(+)CD3(-) NK cells was inversely correlated with the 28-joint DAS (DAS28). In TCZ-treated patients, the baseline proportion of CD3(-)CD56(+) NK cells was inversely correlated with the change in DAS28 at 3 months and the proportion was 3-fold greater for patients with DAS28 remission at 3 months than other patients. Change in the proportion of CD56(bri)CD16(-) NK cells was linearly correlated with change in the DAS28 at 3 months. The baseline proportion of NK cells did not predict change in disease activity at 3 months with anti-TNF therapy. The perforin content in NK cells increased with TCZ treatment. CONCLUSION: This study supports NK cell involvement in RA and in the TCZ mechanism of action. NK cells at baseline could be a predictive factor of TCZ response if results are confirmed.

Regulatory B10 cells are decreased in patients with rheumatoid arthritis and are inversely correlated with disease activity.

OBJECTIVE: Regulatory interleukin-10 (IL-10)-producing B cells (B10 cells) have been shown to prevent and cure collagen-induced arthritis in mice. In humans, very little is known about B10 cells in rheumatoid arthritis (RA). Several B cell subsets, such as CD24(high) CD38(high) , CD24(high) CD27+, and CD5+ B cells, were suggested to be precursors of B10 cells. We aimed to analyze these B cell subsets and B10 cells in RA patients and healthy controls. METHODS: B10 cells were generated from peripheral blood mononuclear cells stimulated for 24 hours with CpG and for 4 hours with phorbol 12-myristate 13-acetate/ionomycin/brefeldin A. Intracellular B cell IL-10 was assessed by flow cytometry. Thirty-one controls and 99 RA patients were included. RESULTS: After multiple adjustments, levels of CD24(high) CD38(high) , CD24(high) CD27+, and CD5+ B cells were found to be similar in RA patients and controls. Levels of B10 cells were lower in RA patients than in controls, especially in patients with RA of ≤5 years' duration. Levels of B10 cells correlated inversely with the Disease Activity Score in 28 joints. This was more pronounced in patients with RA of ≤5 years' duration, in whom B10 cells also correlated inversely with C-reactive protein levels. Moreover, B10 cells correlated inversely with rheumatoid factor levels. CD24(high) CD38(high) and CD24(high) CD27+ B cells induced more Treg cells than did CD24(low) B cells in controls but not in RA patients. CONCLUSION: The ability of B cells to produce IL-10 was altered in RA, and this impairment influenced disease activity, biologic inflammation, and autoantibody levels, especially in patients with RA of ≤5 years' duration. This strongly suggests a role of B10 cells in RA initiation.

High levels of memory B cells are associated with response to a first tumor necrosis factor inhibitor in patients with rheumatoid arthritis in a longitudinal prospective study.

INTRODUCTION: Tumor necrosis factor inhibitor (TNFi) therapy is effective for rheumatoid arthritis (RA). Some researchers have suggested that TNFi therapy affects B-cell homeostasis. We studied the effect of TNFi therapy on the distribution of peripheral B-cell subsets to elucidate B-cell-related biomarkers to predict the TNFi response. METHODS: Peripheral B cells were analyzed for expression of CD19, CD27, CD38 and immunoglobulin D in 31 healthy donors and 96 RA patients, including 21 patients who were followed 3 months after TNFi initiation. RESULTS: Treatment with steroids significantly altered the distribution of B-cell subsets. After we adjusted for age, sex and steroid dose, we found that patients with RA had B-cell subset proportions similar to controls. B-cell subset distributions did not differ upon use of TNFi at baseline or before or after TNFi introduction. TNFi responders (according to European League Against Rheumatism criteria) at 3 months had significantly higher proportions of CD27⁺ memory B cells at baseline, and ≥26% CD27⁺ cells at inclusion was associated with a relative risk of 4.9 (1.3 to 18.6) for response to TNFi treatment. CD27⁺ cells produced three times more TNFα than did TNFi-naïve B cells and were correlated with interferon γ produced from CD4⁺ cells in patients without TNFi treatment. CONCLUSIONS: In patients with RA, high levels of baseline memory B cells were associated with response to TNFi, which may be related to TNFα-dependent activation of the T helper type 1 cell pathway.