In vitro Expansion of Treg Cells
To completely understand the mechanism of Treg-mediated immune suppression, protocols have been developed for the in vitro expansion of Tregs isolated from both mouse and human. Tregs have been found to express high levels of growth inhibitory genes including SOCS1 and 2, CTLA-4, and PD1. Therefore, strong signals through TCR / CD28 and IL-2R are thought to be required to overcome the cell cycle arrest of Tregs. Even with established protocols, the challenge to prepare high quality functionally suppressive Tregs with a minimum contamination of effector and non-suppressive T cells remains. To expand Tregs, it has been shown that high concentrations of key cytokines including IL-2 and TGF beta as well as TCR signaling are the essential components required to generate large numbers of either human or murine Tregs. In this approach, IL-2 and TCR signaling antibodies induce T cell proliferation and the addition of TGF beta directs cells towards the T regulatory phenotype by preventing apoptosis and driving conversion of naive CD4 T cells into Tregs with preferentially high expression levels of Foxp3. Experiments have shown that the intensity and sustainability of induced Foxp3 expression is directly proportional to the amount of TGF beta added, which in turn determines the efficacy of Treg suppression.
GITR engagement preferentially enhances proliferation of functionally competent CD4+CD25+FoxP3+ regulatory T cells. Liao G, Nayak S, Regueiro JR, Berger SB, Detre C, Romero X, de Waal Malefyt R, Chatila TA, Herzog RW, Terhorst C. Int Immunol. 2010 Feb 5.
Development of CD4+CD25+FoxP3+ regulatory T cells from cord blood hematopoietic progenitor cells. Hutton JF, Gargett T, Sadlon TJ, Bresatz S, Brown CY, Zola H, Shannon MF, D'Andrea RJ, Barry SC. J Leukoc Biol. 2009 Mar;85(3):445-51.
Isolation, expansion, and characterization of human natural and adaptive regulatory T cells. Gregori S, Bacchetta R, Passerini L, Levings MK, Roncarolo MG. Methods Mol Biol. 2007;380:83-105. Review.