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Cell-Type Specificity of l-Leucyl l-Leucine Methyl Ester

https://doi.org/10.1006/bbrc.2000.2836Get rights and content

Abstract

l-Leucyl l-leucine methyl ester (LeuLeuOMe) is a lysosomotropic agent which is converted to a membranolytic compound by dipeptidyl peptidase I and kills human leukocytes such as CD8+ T cells and monocytes but not B cells. The reagent has also been used in mice on the assumption that the cell-type specificity to murine leukocytes is the same as that to human leukocytes. During study on the effect of LeuLeuOMe on antigen-driven IL-2 production using murine splenocytes as antigen-presenting cells, however, we noticed that murine B cells were sensitive to LeuLeuOMe. We therefore examined the cell-type specificity using murine splenocytes and peritoneal macrophages. Flow cytometric analysis revealed that the most sensitive cells to LeuLeuOMe were CD8+ cells and that CD19+ cells (B cells) were as sensitive as CD3+ cells (T cells). Murine splenic B cells, which were either positively or negatively sorted with a cell sorter, were also sensitive to LeuLeuOMe, whereas human peripheral blood B cells, which were positively sorted, were not. Peritoneal macrophages were the most insensitive to LeuLeuOMe. Thus, this study demonstrated that the cell-type specificity to murine leukocytes is different from that to human leukocytes.

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    Finally, lysosomal membrane integrity is lost, resulting in caspase activation and apoptosis (35). Various cells exhibit different sensitivity toward LeuLeuOMe, the most sensitive being the cytotoxic lymphocytes (36, 37). Because of their reasonably high content of Bid and various cathepsins including cathepsin C, we chose HeLa cells as a cellular model to investigate this process.

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