Cutting Edge: l-Arginine Transfer from Antigen-Presenting Cells Sustains CD4+ T Cell Viability and Proliferation.

Metabolomics analyses suggest changes in amino acid abundance, particularly l-arginine (L-ARG), occur in patients with tuberculosis. Immune cells require L-ARG to fuel effector functions following infection. We have previously described an L-ARG synthesis pathway in immune cells; however, its role in APCs has yet to be uncovered. Using a coculture system with mycobacterial-specific CD4+ T cells, we show APC L-ARG synthesis supported T cell viability and proliferation, and activated T cells contained APC-derived L-ARG. We hypothesize that APCs supply L-ARG to support T cell activation under nutrient-limiting conditions. This work expands the current model of APC-T cell interactions and provides insight into the effects of nutrient availability in immune cells.

Promotion of Anti-Tuberculosis Macrophage Activity by L-Arginine in the Absence of Nitric Oxide.

Macrophages are indispensable immune cells tasked at eliminating intracellular pathogens. Mycobacterium tuberculosis (Mtb), one of the most virulent intracellular bacterial pathogens known to man, infects and resides within macrophages. While macrophages can be provoked by extracellular stimuli to inhibit and kill Mtb bacilli, these host defense mechanisms can be blocked by limiting nutritional metabolites, such as amino acids. The amino acid L-arginine has been well described to enhance immune function, especially in the context of driving macrophage nitric oxide (NO) production in mice. In this study, we aimed to establish the necessity of L-arginine on anti-Mtb macrophage function independent of NO. Utilizing an in vitro system, we identified that macrophages relied on NO for only half of their L-arginine-mediated host defenses and this L-arginine-mediated defense in the absence of NO was associated with enhanced macrophage numbers and viability. Additionally, we observed macrophage glycolysis to be driven by both L-arginine and mechanistic target of rapamycin (mTOR), and inhibition of glycolysis or mTOR reduced macrophage control of Mtb as well as macrophage number and viability in the presence of L-arginine. Our data underscore L-arginine as an essential nutrient for macrophage function, not only by fueling anti-mycobacterial NO production, but also as a central regulator of macrophage metabolism and additional host defense mechanisms.

Transcription factors WT1 and p53 combined: a prognostic biomarker in ovarian cancer.

BACKGROUND: New approaches to ovarian cancer are needed to improve survival. Wilms' tumour 1 (WT1) is a tumour-associated antigen expressed in many ovarian cancers. P53 is also often altered. The clinical significance of the combined expression of these two transcription factors has not been studied. METHODS: One hundred ninety-six ovarian tumours were classified histopathologically. Tumours were stained for WT1 and p53 immunohistochemically. Stains were analysed according to tumour type, grade and FIGO stage. Kaplan-Meier analyses on 96 invasive carcinomas determined whether categorical variables were related to survival. RESULTS: WT1 and p53 were related to ovarian tumour type, grade, FIGO stage and patient survival. Uniform nuclear p53 expression was associated with invasion and WT1 expression was associated with advanced grade, FIGO stage and poor survival. When WT1 and p53 were both in the age-adjusted Cox model, WT1 was significant while p53 was not. When we combined tumours expressing WT1 and p53, then adjusted for age and tumour subtype, the hazard ratio compared to tumours without WT1 and with normal p53 was 2.70; when adjusted for age and FIGO stage, the hazard ratio was 2.40. CONCLUSIONS: WT1, an antigen target, is a biomarker for poor prognosis, particularly when combined with altered p53.