Michael S Kuhns
Associate Professor, Immunobiology
Associate Professor, BIO5 Institute
Associate Professor, Genetics - GIDP
Primary Department
Department Affiliations
(520) 626-6461
Work Summary
Michael Kuhns' research program is focused on (i) increasing our basic understanding of how T cell fate decisions are made (e.g. development, activation, differentiation, effector functions), and (ii) increasing their working knowledge of how to manipulate these decisions to direct T cells towards a desired outcome, such as increasing responses to vaccines or tumors, preventing transplant rejection, or attenuating autoimmunity.
Research Interest
What we’re interested in: For all vertebrates, from mice to humans, vaccine-induced and naturally primed immunity to pathogens require that coordinated, multi-cellular responses emerge from a myriad of ‘conversations’ that take place between cells of the immune system. These conversations occur via cytokines and chemokines that are secreted by one cell and detected via receptors on other cells. They also occur via direct contacts between membrane-bound molecules at the interface between two cells. Ultimately, these conversations are responsible for insuring that an appropriate immune response occurs in the appropriate place, and at the appropriate time, to fight an infection without inducing an inappropriate response to commensal organisms or self-antigens. The molecules on T cells that are involved in these conversations include but are not limited to: the T cell receptor (TCR), which provides clonotypic antigen specificity to T cells; the CD3δε, γε, and ζζ signaling dimers that connect the TCR to the intracellular signaling machinery; the CD8 and CD4 coreceptors that provide major histocompatibility molecule (MHC)-restriction for T cells that recognize antigenic peptides bound to class I or II MHC, respectively; and costimulatory molecules, such as CD28, that provide information about the activation state of an antigen presenting cell (APC) and thus the context in which an antigen occurs. We are interested in understanding how the individual contributions from this chorus of molecules are integrated to achieve the critical balance between tolerance of self-antigens and protective immunity against pathogenic infection. Specifically, we are working to understand how the information that is critical for T cells to decide if and how they should respond to antigen is conveyed from an antigen presenting cell (APC) to a T cell. We are using a variety of classic molecular, cellular, and biochemical techniques, as well as more modern live cell imaging approaches, to probe the molecular mechanisms involved in these processes. We are also developing mouse model systems to determine how individual mechanisms contribute to T cell responses in vivo during pathogenic infection or autoimmunity. Altogether, our work is aimed at increasing our basic and practical appreciation of T cell responses and regulation.

Publications

Glassman, C. R., Parrish, H. L., Deshpande, N. R., & Kuhns, M. S. (2016). The CD4 and CD3δε Cytosolic Juxtamembrane Regions Are Proximal within a Compact TCR-CD3-pMHC-CD4 Macrocomplex. Journal of immunology (Baltimore, Md. : 1950), 196(11), 4713-22.

TCRs relay information about peptides embedded within MHC molecules (pMHC) to the ITAMs of the associated CD3γε, CD3δε, and CD3ζζ signaling modules. CD4 then recruits the Src kinase p56(Lck) (Lck) to the TCR-CD3 complex to phosphorylate the ITAMs, initiate intracellular signaling, and drive CD4(+) T cell fate decisions. Whereas the six ITAMs of CD3ζζ are key determinants of T cell development, activation, and the execution of effector functions, multiple models predict that CD4 recruits Lck proximal to the four ITAMs of the CD3 heterodimers. We tested these models by placing FRET probes at the cytosolic juxtamembrane regions of CD4 and the CD3 subunits to evaluate their relationship upon pMHC engagement in mouse cell lines. The data are consistent with a compact assembly in which CD4 is proximal to CD3δε, CD3ζζ resides behind the TCR, and CD3γε is offset from CD3δε. These results advance our understanding of the architecture of the TCR-CD3-pMHC-CD4 macrocomplex and point to regions of high CD4-Lck + ITAM concentrations therein. The findings thus have implications for TCR signaling, as phosphorylation of the CD3 ITAMs by CD4-associated Lck is important for CD4(+) T cell fate decisions.

Bethune, M. T., Gee, M. H., Bunse, M., Lee, M. S., Gschweng, E. H., Pagadala, M. S., Zhou, J., Cheng, D., Heath, J. R., Kohn, D. B., Kuhns, M. S., Uckert, W., & Baltimore, D. (2016). Domain-swapped T cell receptors improve the safety of TCR gene therapy. eLife, 5.

T cells engineered to express a tumor-specific αβ T cell receptor (TCR) mediate anti-tumor immunity. However, mispairing of the therapeutic αβ chains with endogenous αβ chains reduces therapeutic TCR surface expression and generates self-reactive TCRs. We report a general strategy to prevent TCR mispairing: swapping constant domains between the α and β chains of a therapeutic TCR. When paired, domain-swapped (ds)TCRs assemble with CD3, express on the cell surface, and mediate antigen-specific T cell responses. By contrast, dsTCR chains mispaired with endogenous chains cannot properly assemble with CD3 or signal, preventing autoimmunity. We validate this approach in cell-based assays and in a mouse model of TCR gene transfer-induced graft-versus-host disease. We also validate a related approach whereby replacement of αβ TCR domains with corresponding γδ TCR domains yields a functional TCR that does not mispair. This work enables the design of safer TCR gene therapies for cancer immunotherapy.

Parrish, H. L., Deshpande, N. R., Vasic, J., & Kuhns, M. S. (2016). Functional evidence for TCR-intrinsic specificity for MHCII. Proceedings of the National Academy of Sciences of the United States of America.

How T cells become restricted to binding antigenic peptides within class I or class II major histocompatibility complex molecules (pMHCI or pMHCII, respectively) via clonotypic T-cell receptors (TCRs) remains debated. During development, if TCR-pMHC interactions exceed an affinity threshold, a signal is generated that positively selects the thymocyte to become a mature CD4(+) or CD8(+) T cell that can recognize foreign peptides within MHCII or MHCI, respectively. But whether TCRs possess an intrinsic, subthreshold specificity for MHC that facilitates sampling of the peptides within MHC during positive selection or T-cell activation is undefined. Here we asked if increasing the frequency of lymphocyte-specific protein tyrosine kinase (Lck)-associated CD4 molecules in T-cell hybridomas would allow for the detection of subthreshold TCR-MHC interactions. The reactivity of 10 distinct TCRs was assessed in response to selecting and nonselecting MHCII bearing cognate, null, or "shaved" peptides with alanine substitutions at known TCR contact residues: Three of the TCRs were selected on MHCII and have defined peptide specificity, two were selected on MHCI and have a known pMHC specificity, and five were generated in vitro without defined selecting or cognate pMHC. Our central finding is that IL-2 was made when each TCR interacted with selecting or nonselecting MHCII presenting shaved peptides. These responses were abrogated by anti-CD4 antibodies and mutagenesis of CD4. They were also inhibited by anti-MHC antibodies that block TCR-MHCII interactions. We interpret these data as functional evidence for TCR-intrinsic specificity for MHCII.

Kuhns, M. S., Girvin, A. T., Klein, L. O., Chen, R., Jensen, K. D., Newell, E. W., Huppa, J. B., Lillemeier, B. F., Huse, M., Chien, Y., Garcia, K. C., & Davis, M. M. (2010). Evidence for a functional sidedness to the alphabetaTCR. Proceedings of the National Academy of Sciences of the United States of America, 107(11), 5094-9.

The T cell receptor (TCR) and associated CD3gammaepsilon, deltaepsilon, and zetazeta signaling dimers allow T cells to discriminate between different antigens and respond accordingly, but our knowledge of how these parts fit and work together is incomplete. In this study, we provide additional evidence that the CD3 heterodimers congregate on one side of the TCR in both the alphabeta and gammadeltaTCR-CD3 complexes. We also report that the other side of the alphabetaTCR mediates homotypic alphabetaTCR interactions and signaling. Specifically, an erythropoietin receptor-based dimerization assay was used to show that, upon complex assembly, the CD3epsilon chains of two CD3 heterodimers are arranged side-by-side in both the alphabeta and gammadeltaTCR-CD3 complexes. This system was also used to show that alphabetaTCRs can dimerize in the cell membrane and that mutating the unusual outer strands of the Calpha domain impairs this dimerization. Finally, we present data showing that, for CD4 T cells, the mutations that impair alphabetaTCR dimerization also alter ligand-induced calcium mobilization, TCR accumulation at the site of pMHC contact, and polarization toward the site of antigen contact. These data reveal a "functional-sidedness" to the alphabetaTCR constant region, with dimerization occurring on the side of the TCR opposite from where the CD3 heterodimers are located.

Chambers, C. A., Kuhns, M. S., Egen, J. G., & Allison, J. P. (2001). CTLA-4-mediated inhibition in regulation of T cell responses: mechanisms and manipulation in tumor immunotherapy. Annual review of immunology, 19, 565-94.

The T cell compartment of adaptive immunity provides vertebrates with the potential to survey for and respond specifically to an incredible diversity of antigens. The T cell repertoire must be carefully regulated to prevent unwanted responses to self. In the periphery, one important level of regulation is the action of costimulatory signals in concert with T cell antigen-receptor (TCR) signals to promote full T cell activation. The past few years have revealed that costimulation is quite complex, involving an integration of activating signals and inhibitory signals from CD28 and CTLA-4 molecules, respectively, with TCR signals to determine the outcome of a T cell's encounter with antigen. Newly emerging data suggest that inhibitory signals mediated by CTLA-4 not only can determine whether T cells become activated, but also can play a role in regulating the clonal representation in a polyclonal response. This review primarily focuses on the cellular and molecular mechanisms of regulation by CTLA-4 and its manipulation as a strategy for tumor immunotherapy.