Scientists at University of Alabama describe research in immunology
2007 NOV 21 -- "CD4(+)CD25(+) regulatory T cells (Tregs) inhibit immune responses to a variety of Ags, but their specificity and mechanism of suppression are controversial. This controversy is largely because many studies focused on natural Tregs with undefined specificities and suppression has frequently been measured on polyclonal T cell responses," scientists writing in the Journal of Immunology report. "To address the issue of specificity further, we have bred K-d -specific, CD4(+) TCR (TCR75) transgenic mice to Foxp3(gfp) knockin reporter mice to permit sorting of Tregs with a known specificity. Foxp3(gfp)center dot TCR75 mice did not express significant numbers of natural FoxP3(+) Tregs expressing the TCR75 transgenes, but FoxP3 expression was induced by stimulating with K (d) plus TGF-beta. The resulting GFP(+) TCR75 cells were anergic, whereas the GFP(-) TCR75 cells proliferated upon restimulation with K d peptide. Yet both exhibited severely reduced expression of intracellular IFN-gamma and TNF-alpha upon restimulation. GFP(+), but not GFP(-), TCR75 T cells suppressed responses by naive TCR75 T cells and by nontransgenic spleen cells stimulated with anti-CD3. GFP(+) TCR75 cells also inhibited polyclonal C57BL/6 anti-K-d d d CTL responses if the APC expressed K-d and both MHC class I and class II, and responses by OT1 T cells to B6 center dot K-d center dot OVA but not B6 center dot K-d plus OVA expressing APC, demonstrating linked-suppression of CD8 responses. Thus, Tregs exhibit a greater degree of specificity in vitro than previously appreciated," wrote J.A. Kapp and colleagues, University of Alabama. The researchers concluded: "The observation that Tregs and responder T cells must recognize the same APC provides a mechanistic explanation for the observation that Tregs must be in direct contact with effector T cells to suppress their responses." Kapp and colleagues published their study in the Journal of Immunology (Antigen, in the presence of TGF-beta, induces up-regulation of FoxP3(Gfp+) in CD4(+) TCR transgenic T cells that mediate linked suppression of CD8(+) T cell responses. Journal of Immunology, 2007;179(4):2105-2114). Additional information can be obtained by contacting J.A. Kapp, University of Alabama, Dept. of Ophthalmology, Room W287 Spain Wallace Bldg, 619 S 19tth St., Birmingham, AL 35294, USA. The publisher of the Journal of Immunology can be contacted at: American Association Immunologists, 9650 Rockville Pike, Bethesda, MD 20814, USA. Keywords: United States, Birmingham, Immunology, University of Alabama. This article was prepared by Immunotherapy Weekly editors from staff and other reports. Copyright 2007, Immunotherapy Weekly via NewsRx.com.
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