ABSTRACT
While CD69 may regulate thymocyte egress by inhibiting S1P1 expression, CD69 expression is not thought to be required for normal thymocyte development. Here we show that CD69 is in fact specifically required for the differentiation of mature NKT2 cells, which do not themselves express CD69. Mechanistically, CD69 expression is required on CD24+ PLZFhi innate precursors for their retention in the thymus and completion of their differentiation into mature NKT2 cells. By contrast, CD69-deficient CD24+ PLZFhi innate precursors express S1P1 and prematurely exit the thymus, while S1P1 inhibitor treatment of CD69-deficient mice retains CD24+ PLZFhi innate precursors in the thymus and restores NKT2 cell differentiation. Thus, CD69 prevents S1P1 expression on CD24+ PLZFhi innate precursor cells from aborting NKT2 differentiation in the thymus. This study reveals the importance of CD69 to prolong the thymic residency time of developing immature precursors for proper differentiation of a T cell subset.
Subject(s)
Antigens, CD/genetics , Antigens, Differentiation, T-Lymphocyte/genetics , Lectins, C-Type/genetics , Lymphopoiesis/genetics , Natural Killer T-Cells/cytology , Receptors, Lysosphingolipid/genetics , T-Lymphocyte Subsets/cytology , Thymocytes/cytology , Animals , CD24 Antigen/metabolism , Cell Differentiation , Gene Expression Regulation , Mice , Mice, Knockout , Natural Killer T-Cells/metabolism , Promyelocytic Leukemia Zinc Finger Protein/metabolism , Sphingosine-1-Phosphate Receptors , T-Lymphocyte Subsets/metabolism , Thymocytes/metabolismABSTRACT
We have recently found that millimolar concentrations of sodium fluoride (NaF) induced apoptotic cell death, characterized by caspase activation and DNA fragmentation, in tumor cell lines. This finding paved the way to investigating the interaction between NaF and the oral environment. As an initial step, we investigated redox compounds, metals and saliva, which may modify the cytotoxic activity of NaF against a human oral squamous cell carcinoma cell line (HSC-2). The minimum exposure time to NaF required for cytotoxicity induction was 8 hours. Noncytotoxic concentrations of antioxidants (sodium ascorbate, gallic acid, epigallocatechin gallate, chlorogenic acid, curcumin, superoxide dismutase, catalase), oxidants (hydrogen peroxide, sodium hypochlorite), metals (CuCl, CuCl2, FeCl2, FeCl3, CoCl2) or saliva neither protected against, nor enhanced the cytotoxic activity of NaF. Cytotoxic concentrations of these compounds produced somewhat additive, but not synergistic, effects on the cytotoxicity of NaF. ESR analysis demonstrated that NaF did not apparently change the radical intensity of sodium ascorbate and gallic acid, measured under alkaline conditions. During the cell death induction in human promyelocytic leukemia HL-60 cells by NaF, the consumption of glucose rapidly declined, followed by a decline in the consumption of major amino acids. The present study suggests that the cytotoxic activity of NaF is not regulated by the redox mechanism, but rather linked to the rapid decline in glucose consumption at early stage.
