Marisa Alegre, M.D., Ph.D.

T Cell Tolerance and Inhibitors of T Cell Function.

Research Summary

The research in my lab focuses on mechanisms of inactivation of T cells and T cell tolerance. We are interested in T cell receptors such as CTLA-4 and PD-1 that inhibit T cell responses as well as in the biochemical pathways in T cells that can be inhibited to achieve donor-specific tolerance in vivo in models of autoimmunity and transplantation.

T cells are activated through recognition of antigenic peptides by the T cell receptor concurrently to signals delivered by ligation of costimulatory receptors expressed on the cell surface. Upon activation, T cells upregulate receptors that can terminate T cell activation either through inducing cell-cycle arrest or apoptosis. CTLA-4 is one such molecule. We have found that CTLA4 is upregulated following T cell activation, and cycles from large intracellular pools to small regions on the surface of T lymphocyes. Surface CTLA4 is endocytosed following association with the clathrin adaptor AP50, but phosphorylation of a tyrosine in the cytoplasmic tail of CTLA4 allows retention on the cell surface. Different projects in the lab involve the search for molecules that may mediate the inhibitory signals delivered by CTLA4, as well as the effects of overexpression of CTLA-4 in T cells in models of autoimmunity and transplantation. For these projects, we are taking advantage of mice that have been made deficient in CTLA4 by gene targeting, and that we have crossed to T cell receptors of unique specificities, and of mice that over express CTLA-4 selectively in T cells.

In an effort to understand the biochemical pathways in T cells that are essential for the initiation of autoimmune diseases or of acute allograft rejection and that could potentially be targeted to achieve tolerance, we have focused on the importance of transcription factors. In particular, we are studying the role of NF-kB activation in T cells for the initiation of autoimmune diseases and acute allograft rejection. To this end, we are using mice with impaired NF-kB activation in T cells. These mice reject skin allografts but permanently accept cardiac allografts. Moreover, mice tolerant to cardiac allografts subsequently accept skin grafts from the same donor and show donor-specific tolerance. A major thrust in the laboratory is to characterize the mechanism of donor-specific tolerance in these animals as well as explore the role of NF-kB activation in T cells in the rejection of islet allografts and the initiation of autoimmune diseases such as diabetes.

Therefore, our current research focuses on the molecular and biochemical properties of T cell inhibitory receptors in vitro as well as on the roles of these receptors in transplantation and autoimmune diseases in vivo.

Selected Papers

Wissing M, Desalle F, Abramowicz D, Willems F, Leo O, Goldman M, Alegre ML.  The administration of an anti-CD3 mAb in mice differentially regulates the production of cytokines upon restimulation: implications for allogeneic skin graft survival.  Transplantation, 68:677, 1999.

Alegre ML.  Costimulatory molecules as targets for the induction of transplantation tolerance.  Nephrology Dialysis Transplantation, 14:322, 1999.

Zhou P, Szot GL, Guo Z, Kim O, He G, Wang J, Grusby MJ, Newell KA, Thistlethwaite JR, Bluestone JA, Alegre ML.  Role of STAT4 and STAT6 signaling in allograft rejection and CTLA4-Ig-mediated tolerance.  J.Immunol., 165:5580, 2000.

Gajewski TF, Fallarino F, Chang C, Rivas F, Shiels H, Fields PE, Alegre ML.  Absence of CTLA-4 lowers the threshold of primed CD8+ TCR transgenic T cells.  J. Immunol., 166:3900, 2001.

Szot GL, Zhou P, Rulifson I, Wang J, Guo Z, Kim O, Newell KA, Thistlethwaite JR, Bluestone JA, Alegre ML.  Different mechanisms of cardiac allograft rejection in wildtype and CD28-deficient mice.  Am. J. Transplantation, 1:38, 2001.

Alegre ML, Gajewski TF.  CTLA-4: its role in the immune response.  CTLA-4 in autoimmune diseases, Landes Bioscience, 2001.
Chin R. Zhou P, Alegre ML, Fu YX.  Confounding factors complicate conclusions in aly model.  Nature Medicine (letter), 7:1165, 2001.

Alegre ML, Frauwirth KA, Thompson CB.  T cell regulation by CD28 and CTLA-4.  Nature Reviews in Immunology 1:220-228, 2001.

Harlin H, Podack E, Booothby M, Alegre ML.  TCR-independent CD30 signaling selectively induces IL-13 production via a TRAF/p38 MAPK-dependent mechanism.  J. Immunol., 169:2451-2459, 2002.

Harlin H, Hwang KW, Palucki D, Kim O, Thompson CB, Boothby M, Alegre ML.  CTLA-4-engagement regulates NF-κB activation in vivo.  Eur. J. Immunol., 32:2095-2104, 2002.

Hwang KW, Sweatt WB, Brown IE, Blank C, Gajewski TF, Bluestone JA, Alegre ML.   CUTTING EDGE: Targeted ligation of CTLA-4 in vivo by membrane-bound anti-CTLA-4 antibody prevents rejection of allogeneic cells.  J. Immunol., 169:2451-2459, 2002.

Zhou P, Hwang. KW, Palucki DA, Guo Z, Boothby M, Newell KA, Alegre ML.  Impaired NF-κB activation permits tolerance to primary heart allografts and secondary skin grafts.  Am. J. Transplant., 3:139-147, 2003.

Zhou P, Hwang KW, Palucki DA, Kim O, Newell KA, Fu YX, Alegre ML.  Secondary lymphoid organs are important but not absolutely required for allograft responses.  Am. J. Transplant., 3:359-366, 2003.

Fallarino F, Grohmann U, Hwang KW, Orabona C, Vacca C, Bianchi R, Belladonna ML, Fioretti MC, Alegre ML, Puccetti P.  Modulation of tryptophan catabolism by regulatory T cells.  Nature Immunology, 4:1206-1212, 2003.

Subudhi SK, Zhou P, Yerian LM, Chin RK, Lo JC, Anders RA, Sun Y, Chen L, Wang Y, Alegre ML*, Fu YX*.  B7-H1 costimulation promotes T cell-mediated autoimmune diabetes and islet transplantation rejection. J. Clin. Invest., 113:694-700, 2004 (* co-last authors).

Rivas FV, O'Keefe JP, Alegre ML, Gajewski TF. The actin cytoskeleton regulates calcium dynamics and NFAT nuclear duration. Mol. Cellular Biol., 24:1628-1639, 2004.

O’Keefe JP, Blaine K, Alegre ML, Gajewski TF.  cSMAc formation is not required for activation of naïve CD8+ T cells.  Proc. Natl. Acad. Sci. U.S.A., 101:9351-9356, 2004.

Alegre ML.  Targeting NF-κB in the immune system to prevent acute allograft rejection.  Curr. Opin. Organ Transpl., 9:252-257, 2004.

Hwang KW, Sweatt WB, Mashayekhi M, Palucki DA, Sattar H, Chuang E, Alegre ML.  Transgenic expression of CTLA-4 controls lymphoproliferation in IL-2-deficient mice.  J. Immunol., 173:5415-5424, 2004.

Zhou P*, Balin SJ*, Mashayekhi M, Hwang KW, Palucki DA, Alegre ML.  T cell depletion but not T cell regulation plays a role in transplantation tolerance in mice with reduced T cell-intrinsic NF-κB activation.  J. Immunol., 174:3447-53, 2005 (*co-first authors).

McNerney ME*, Lee KM*, Zhou P*, Molinero L, Mashayekhi M, Guzior D, Sattar H, Kuppireddi S, Wang CR, Vinay Kumar*, Alegre ML*.  Role of NK cell subsets in cardiac allograft rejection.  Am. J. Transplant., 6:505-513, 2006 (*co-first and co-last authors).

Chen L, Wang T, Zhou P, Ma L, Yin D, Shen J, Molinero L, Nozaki T, Phillips T, Uematsu S, Akira S, Wang CR, Fairchild RL, Alegre ML*, Chong A*.  TLR engagement prevents transplantation tolerance. Am. J. Transplant., 6:505-513, 2006.  (*co-last authors).

Vilimas T, Mascarenhas J, Mandal M, Buonamici S, Palomero T, Meng F, Macaroun S, Alegre ML, Ferrando A, Kee B, Miele L, Aifantis I.  Targeting the NF-κB signaling pathway in Notch1-induced T cell leukemia.  Nature Medicine, 13:70-7, 2007.

Chen L, Hussien Y, Hwang KW, Wang Y, Zhou P, Alegre ML.  Overexpression of PD-1 in T cells has mild impact on allograft survival.  Transplant Int., 1:21-29, 2008.

Molinero LL, Zhou P, Wang Y, Harlin H, Cosmano J, Yokota Y, Kee B, Abraham C, Alegre ML.  Epidermal Langerhans cells play a major role in skin allograft rejection in mice with NF-κB-impaired T cells.  Am. J. Transplant., 8:21-31 2008.

Qiao G, Li Z, Molinero L, Alegre ML, Ying H, Sun Z, Penninger JM, Zhang J.  T cell receptor-induced NF-κB activation is negatively regulated by E3 ubiquitin ligase Cbl-b.  Mol. Cel. Biol., in press, 2008.

Wang T, Chen L, Ahmed E, Zhou P, Alegre ML*, Chong AS*.  Prevention of transplantation tolerance by bacterial infection with Listeria monocytogenes.  J. Immunol., in press, 2008. (* co-last authors).

Manicassamy S, Yin D, Zhang Z, Molinero LL, Alegre ML, Sun Z. A critical role for PKC-θ-mediated T cell survival in cardiac allograft rejection.  J. Immunol., in press, 2008.