The molecular interactions that mediate signaling of T and B lymphocytes, both during development and in activation of mature T and B cells, are not fully understood. Genetic and biochemical approaches have therefore been taken to address these questions. Costimulatory B7 molecules (B7-1 or CD80;and B7-2 or CD86) are known to bind to T cell costimulatory receptors CD28 and CTLA4. Engagement of CD28 is know to transduce signals in T cells that play a critical role in T cell activation. TCR mediated activation of T cells to proliferation and IL2 secretion was enhanced in mice deficient in the adapter molecule cbl-b, suggesting a negative regulatory role for cbl-b under these conditions. Cbl-b deletion in fact reversed the inability of CD28-deficient mice to generate T cell-dependent Ig class switched primary and secondary antibody responses. The observation that cbl-b inactivation can enhance T cell responses to TCR signaling, and can bypass requirements for CD28 costimulation has been translated to studies of tumor rejection. Inactivation of cbl-b enhances the ability of mice to reject tumors that do not express costimulatory ligands (CD80 or CD86), and that grow progressively in wild type mice. Cbl-b inactivation also dramatically inhibits the incidence of thymic lymphomas in ATM-deficient mice. These findings identify a novel strategy for enhancing T cell-mediated tumor immunotherapy by modulating regulatory influences on T cell activation. Translational efforts are in progress using high throughput screening to identfy molecules that are capable of reproducing the effects of cbl-b inactivation, allowing human T lymphocytes to respond to T cell receptor (TCR) stimuli in the absence of otherwise required CD28-mediate cosimulation. Mutants of B7-1 have been generated and studied that differ in their capacity to dimerize, potentially affecting their interaction with receptors such as CD28 and CTLA4. B7-1 mutants that are obligate covalent dimers are more efficient in supporting conjugates of T cells and antigen-presenting cells (APC) than is the wild-type B7-1 which exists in dynamic equilibrium between monomer and dimer. Obligate dimers are also more efficient in inducing early signaling events in T cells. Paradoxically, however, B7-1 dimers are less potent costimulators of T cell proliferative responses. These findings suggest that reversible transition between monomer and dimer may be critical in the optimal kinetics of interaction involved in costimulation of T cell functional responses necessary for functional responses to antigen, with potential relevance to responses to tumors and infectious agents. The relationship between members of the cbl family and other critical adapter molecules has been studied. Experiments have indicated that inactivation of c-cbl (but not cbl-b) completely reverses the lethal phenotype caused by SLP-76 deficiency. In addition, c-cbl inactivation partially reverses the defect in T cell development caused by deficiency in SLP-76 or LAT, resulting in fact in a marked hyperplasia of peripheral CD4 T cells. These findings indicate an unanticipated SLP-76 (and LAT) independent signaling pathway that is facilitated by c-cbl inactivation. The biochemical basis for these effects is under study, using SLP-76 mutants to dissect the structure-function relationships in this pathway. SLP-65 (also termed BLNK) is an adapter molecule that plays a central role in development of B cells, and mice deficient in BLNK manifest severe impairment in early as well as late stages of B cell development. We have observed that inactivation of c-cbl results in substantial rescue of early B cell development by facilitating signaling through the pre-BCR, demonstrating that c-cbl negatively regulates a BLNK-independent pathway of early B cell maturation.The molecular interactions that mediate signaling of T and B lymphocytes, both during development and in activation of mature T and B cells, are not fully understood. Genetic and biochemical approaches have therefore been taken to address these questions. Costimulatory B7 molecules (B7-1 or CD80;and B7-2 or CD86) are known to bind to T cell costimulatory receptors CD28 and CTLA4. Engagement of CD28 is know to transduce signals in T cells that play a critical role in T cell activation. TCR mediated activation of T cells to proliferation and IL2 secretion was enhanced in mice deficient in the adapter molecule cbl-b, suggesting a negative regulatory role for cbl-b under these conditions. Cbl-b deletion in fact reversed the inability of CD28-deficient mice to generate T cell-dependent Ig class switched primary and secondary antibody responses. The observation that cbl-b inactivation can enhance T cell responses to TCR signaling, and can bypass requirements for CD28 costimulation has been translated to studies of tumor rejection. Inactivation of cbl-b enhances the ability of mice to reject tumors that do not express costimulatory ligands (CD80 or CD86), and that grow progressively in wild type mice. Cbl-b inactivation also dramatically inhibits the incidence of thymic lymphomas in ATM-deficient mice. These findings identify a novel strategy for enhancing T cell-mediated tumor immunotherapy by modulating regulatory influences on T cell activation. Translational efforts are in progress using high throughput screening to identfy molecules that are capable of reproducing the effects of cbl-b inactivation, allowing human T lymphocytes to respond to T cell receptor (TCR) stimuli in the absence of otherwise required CD28-mediate cosimulation. Mutants of B7-1 have been generated and studied that differ in their capacity to dimerize, potentially affecting their interaction with receptors such as CD28 and CTLA4. B7-1 mutants that are obligate covalent dimers are more efficient in supporting conjugates of T cells and antigen-presenting cells (APC) than is the wild-type B7-1 which exists in dynamic equilibrium between monomer and dimer. Obligate dimers are also more efficient in inducing early signaling events in T cells. Paradoxically, however, B7-1 dimers are less potent costimulators of T cell proliferative responses. These findings suggest that reversible transition between monomer and dimer may be critical in the optimal kinetics of interaction involved in costimulation of T cell functional responses necessary for functional responses to antigen, with potential relevance to responses to tumors and infectious agents. The relationship between members of the cbl family and other critical adapter molecules has been studied. Experiments have indicated that inactivation of c-cbl (but not cbl-b) completely reverses the lethal phenotype caused by SLP-76 deficiency. In addition, c-cbl inactivation partially reverses the defect in T cell development caused by deficiency in SLP-76 or LAT, resulting in fact in a marked hyperplasia of peripheral CD4 T cells. These findings indicate an unanticipated SLP-76 (and LAT) independent signaling pathway that is facilitated by c-cbl inactivation. The biochemical basis for these effects is under study, using SLP-76 mutants to dissect the structure-function relationships in this pathway. SLP-65 (also termed BLNK) is an adapter molecule that plays a central role in development of B cells, and mice deficient in BLNK manifest severe impairment in early as well as late stages of B cell development. We have observed that inactivation of c-cbl results in substantial rescue of early B cell development by [summary truncated at 7800 characters]

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Investigator-Initiated Intramural Research Projects (ZIA)
Project #
1ZIABC009281-23
Application #
7965153
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
23
Fiscal Year
2009
Total Cost
$791,759
Indirect Cost
Name
National Cancer Institute Division of Basic Sciences
Department
Type
DUNS #
City
State
Country
Zip Code
Watanabe, Masashi; Fujihara, Chiharu; Radtke, Andrea J et al. (2017) Co-stimulatory function in primary germinal center responses: CD40 and B7 are required on distinct antigen-presenting cells. J Exp Med 214:2795-2810
Chiang, Y Jeffrey; Hodes, Richard J (2015) Regulation of T cell development by c-Cbl: essential role of Lck. Int Immunol 27:245-51
Watanabe, Masashi; Moon, Kyung Duk; Vacchio, Melanie S et al. (2014) Downmodulation of tumor suppressor p53 by T cell receptor signaling is critical for antigen-specific CD4(+) T cell responses. Immunity 40:681-91
Williams, Joy A; Zhang, Jingjing; Jeon, Hyein et al. (2014) Thymic medullary epithelium and thymocyte self-tolerance require cooperation between CD28-CD80/86 and CD40-CD40L costimulatory pathways. J Immunol 192:630-40
Chiang, Jeffrey; Hodes, Richard J (2011) Cbl enforces Vav1 dependence and a restricted pathway of T cell development. PLoS One 6:e18542
Bhatia, Sumeena; Sun, Kristine; Almo, Steven C et al. (2010) Dynamic equilibrium of B7-1 dimers and monomers differentially affects immunological synapse formation and T cell activation in response to TCR/CD28 stimulation. J Immunol 184:1821-8
Chiang, Y Jeffrey; Jordan, Martha S; Horai, Reiko et al. (2009) Cbl enforces an SLP76-dependent signaling pathway for T cell differentiation. J Biol Chem 284:4429-38