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Immunology. 2008 Sep;125(1):70-9. doi: 10.1111/j.1365-2567.2008.02822.x. Epub 2008 Apr 4.

TcR-induced regulated secretion leads to surface expression of CTLA-4 in CD4+CD25+ T cells.

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Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-1360, USA.


In this study we show that CD4+ T cells develop a functional regulated secretory compartment after differentiation into effector cells, as shown by their increased expression and T-cell receptor-induced exocytosis of lysosomal and cytotoxic effector proteins. We tested the hypothesis that activation-induced surface cytotoxic T-lymphocyte-associated antigen (CTLA-4) expression in CD4+CD25+ regulatory T cells occurs via a similar regulated secretory pathway. Fluorescence microscopy showed that internal CTLA-4 in these cells was stored in a vesicular compartment distinct from lysosomal vesicles. Rapid activation-induced CTLA-4 surface expression in mouse CD4+CD25+ T cells is independent of protein synthesis and Rab-27a. When antigen-dependent T-cell-antigen-presenting cell (APC) conjugates were analysed for surface distribution of CD86 on APC, a higher concentration of CD86 molecules was observed in the synapse of APC conjugated to CD4+CD25+ cells than APC conjugated to CD4+CD25- cells. These results demonstrate that fast delivery of mediators by the regulated secretory pathway in CD4+ T cells can be used to perform other functions that are not involved in cytotoxic function but that can influence/regulate other cells.

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