• 1
    Sharpe, A. H. and Freeman, G. J., The B7-CD28 superfamily. Nat. Rev. Immunol. 2002. 2: 116126.
  • 2
    Bour-Jordan, H. and Blueston, J. A., CD28 function: a balance of costimulatory and regulatory signals. J. Clin. Immunol. 2002. 22: 17.
  • 3
    Lohr, J., Knoechel, B., Jiang, S., Sharpe, A. H. and Abbas, A. K., The inhibitory function of B7 costimulators in T cell responses to foreign and self-antigens. Nat. Immunol. 2003. 4: 664669.
  • 4
    Salomon, B., Lenschow, D. J., Rhee, L., Ashourian, N., Singh, B., Sharpe, A. and Bluestone, J. A., B7/CD28 costimulation is essential for the homeostasis of the CD4+CD25+ immunoregulatory T cells that control autoimmune diabetes. Immunity 2000. 12: 431440.
  • 5
    Tai, X., Cowan, M., Feigenbaum, L. and Singer, A., CD28 costimulation of developing thymocytes induces Foxp3 expression and regulatory T cell differentiation independently of interleukin 2. Nat. Immunol. 2005. 6: 152162.
  • 6
    Tang, Q., Henriksen, K. J., Boden, E. K., Tooley, A. J., Ye, J., Subudhi, S. K., Zheng, X. X. et al.,Cutting edge: CD28 controls peripheral homeostasis of CD4+CD25+ regulatory T cells. J. Immunol. 2003. 171: 33483352.
  • 7
    Schimpl, A., Berberich, I., Kneitz, B., Kramer, S., Santner-Nanan, B., Wagner, S., Wolf, M. et al.,IL-2 and autoimmune disease. Cytokine Growth Factor Rev. 2002. 13: 369378.
  • 8
    Kramer, S., Schimpl, A. and Hunig, T., Immunopathology of interleukin (IL) 2-deficient mice: thymus dependence and suppression by thymus-dependent cells with an intact IL-2 gene. J. Exp. Med. 1995. 182: 17691776.
  • 9
    Chambers, C. A., Kuhns, M. S., Egen, J. G. and Allison, J. P., CTLA-4-mediated inhibition in regulation of T cell responses: mechanisms and manipulation in tumor immunotherapy. Annu. Rev. Immunol. 2001. 19: 565594.
  • 10
    Krummel, M. F. and Allison, J. P., CD28 and CTLA-4 have opposing effects on the response of T cells to stimulation. J. Exp. Med. 1995. 182: 459465.
  • 11
    Collins, A. V., Brodie, D. W., Gilbert, R. J., Iaboni, A., Manso-Sancho, R., Walse, B., Stuart, D. I. et al.,The interaction properties of costimulatory molecules revisited. Immunity 2002. 17: 201210.
  • 12
    Qureshi, O. S., Zheng, Y., Nakamura, K., Attridge, K., Manzotti, C., Schmidt, E. M., Baker, J. et al.,Trans-endocytosis of CD80 and CD86: a molecular basis for the cell-extrinsic function of CTLA-4. Science 2011. 332: 600603.
  • 13
    Grohmann, U., Orabona, C., Fallarino, F., Vacca, C., Calcinaro, F., Falorni, A., Candeloro, P. et al.,CTLA-4-Ig regulates tryptophan catabolism in vivo. Nat. Immunol. 2002. 3: 10971101.
  • 14
    Takahashi, T., Tagami, T., Yamazaki, S., Uede, T., Shimizu, J., Sakaguchi, N., Mak, T. W. et al.,Immunologic self-tolerance maintained by CD25(+)CD4(+) regulatory T cells constitutively expressing cytotoxic T lymphocyte-associated antigen 4. J. Exp. Med. 2000. 192: 303310.
  • 15
    Read, S., Malmstrom, V. and Powrie, F., Cytotoxic T lymphocyte-associated antigen 4 plays an essential role in the function of CD25(+)CD4(+) regulatory cells that control intestinal inflammation. J. Exp. Med. 2000. 192: 295302.
  • 16
    Fraser, J. D., Irving, B. A., Crabtree, G. R. and Weiss, A., Regulation of interleukin-2 gene enhancer activity by the T cell accessory molecule CD28. Science 1991. 251: 313316.
  • 17
    Okkenhaug, K., Wu, L., Garza, K. M., La Rose, J., Khoo, W., Odermatt, B., Mak, T. W. et al.,A point mutation in CD28 distinguishes proliferative signals from survival signals. Nat. Immunol. 2001. 2: 325332.
  • 18
    Burr, J. S., Savage, N. D., Messah, G. E., Kimzey, S. L., Shaw, A. S., Arch, R. H. and Green, J. M., Cutting edge: distinct motifs within CD28 regulate T cell proliferation and induction of Bcl-XL. J. Immunol. 2001. 166: 53315335.
  • 19
    Rudd, C. E., Taylor, A. and Schneider, H., CD28 and CTLA-4 coreceptor expression and signal transduction. Immunol. Rev. 2009. 229: 1226.
  • 20
    Li, X. C., Demirci, G., Ferrari-Lacraz, S., Groves, C., Coyle, A., Malek, T. R. and Strom, T. B., IL-15 and IL-2: a matter of life and death for T cells in vivo. Nat. Med. 2001. 7: 114118.
  • 21
    Setoguchi, R., Hori, S., Takahashi, T. and Sakaguchi, S., Homeostatic maintenance of natural Foxp3(+) CD25(+) CD4(+) regulatory T cells by interleukin (IL)-2 and induction of autoimmune disease by IL-2 neutralization. J. Exp. Med. 2005. 201: 723735.
  • 22
    Alegre, M. L., Noel, P. J., Eisfelder, B. J., Chuang, E., Clark, M. R., Reiner, S. L. and Thompson, C. B., Regulation of surface and intracellular expression of CTLA4 on mouse T cells. J. Immunol. 1996. 157: 47624770.
  • 23
    Finn, P. W., He, H., Wang, Y., Wang, Z., Guan, G., Listman, J. and Perkins, D. L., Synergistic induction of CTLA-4 expression by costimulation with TCR plus CD28 signals mediated by increased transcription and messenger ribonucleic acid stability. J. Immunol. 1997. 158: 40744081.
  • 24
    Zheng, Y., Josefowicz, S., Chaudhry, A., Peng, X. P., Forbush, K. and Rudensky, A. Y., Role of conserved non-coding DNA elements in the Foxp3 gene in regulatory T-cell fate. Nature 2010. 463: 808812.
  • 25
    Fisson, S., Darrasse-Jeze, G., Litvinova, E., Septier, F., Klatzmann, D., Liblau, R. and Salomon, B. L., Continuous activation of autoreactive CD4+ CD25+ regulatory T cells in the steady state. J. Exp. Med. 2003. 198: 737746.
  • 26
    Maloy, K. J. and Powrie, F., Fueling regulation: IL-2 keeps CD4+ Treg cells fit. Nat. Immunol. 2005. 6: 10711072.