Field Of Study:
CD4+ T lymphocytes recognize antigenic peptide fragments presented on the surface of antigen presenting cells (APC) by major histocompatiblility complex (MHC) class II proteins. Triggering of the T cell antigen receptor (TCR) by binding to the MHC:peptide ligand induces dramatic morphological changes as the T cell flattens against the APC and increases contact area forming stable T-APC conjugates. This initial antigen recognition is followed by large-scale spatial and temporal molecular rearrangements of plasma membrane proteins and intracellular signaling molecules. These rearrangements lead to the formation of an ordered structure at the T-APC interface termed the immunological synapse. The synapse is involved in T cell signaling as well as the site for delivery of T cell effector functions. We have previously shown that molecules from the APC are transferred to the T cell across the immune synapse in a process called trogocytosis.
Work in our lab focuses on three important areas related to immunological synapse biology:
1.) the impact of the herbicide Atrazine on the activation of CD4+ T cells and the mechanism underlying a significant increase in Foxp3+ regulatory T cells;
2.) The biological consequences on individual T cells after the capture of APC membrane fragments from T-APC immunological synapse, a process termed “trogocytosis”;
3.) the nature of the immunological synapse formed by hyporesponsive (anergic) T cells.
While we use a variety of techniques to examine these questions including flow cytometry, animal experiments, biochemical and molecular biology approaches, the main focus of our research is live cell, 3D imaging.
Work in our lab makes use of fibroblasts transfected with a GFP-tagged MHC:peptide covalent complex as surrogate antigen presenting cells. We also use dendritic cells derived from a transgenic mouse expressing the same GFP-tagged MHC:peptide complex under the control of the MHC class II promoter.
We are using these systems to examine biological significance of intercellular transfer of molecules from APC to T cells (termed trogocytosis). We have previously shown that upon dissociation from APC, T cells capture MHC:peptide molecules from the immunological synapse and imaging data suggests that these molecules continue to signal to the T cell. Our 2012 paper suggests that these trogocytosed molecules sustain intracellular signaling, which leads to selective survival of the trogocytosis positive cells, in vitro. Our working hypothesis is that this controls an ongoing immune response by continuous cell autonomous signaling and by intercellular interactions in T cell – T cell antigen presentation. This T-T presentation may potentiate an immune response and/or may play an important role in peripheral tolerance, as antigen presentation by T cells results in anergy induction in vivo in some experimental systems.
Immunotoxicology of Atrazine
We are examining the impact on Atrazine on thethe activation and differentiation of CD4+ T cells. Atrazine is a very widely applied herbicide that the USGS estimates contaminates 70% of the ground water in the US. It has been linked to birth defects, cancer, immune developmental defects and modulation of immune cell effector functions. We have shown that Atrazine inhibits lymphocyte proliferation and lymphocyte effector function. In addition, we have shown that the frequency of Foxp3 positive regulatory T cells doubles in atrazine-treated cultures. We have recently found that male and female T cells repsonde differently to atrazine exposure. We are now examining the impact of Atrazine-induced elevated estrogen on lymphocyte activation, differentation, and an ongoing immune response, both in vitro and in vivo.
Anergic T Cell Immune Synapses
Finally, we are interested in characterizing the immunological synapses formed by cells rendered anergic by recognizing antigen on costimulation deficient APC. We have observed that known negative regulators of TCR signaling, c-Cbl and Cbl-b, are preferentially recruited to the immunological synapse formed by anergic cells. We have also reported that converting a negative signal from the small G-protein Rap1 by expression of B-Raf prevents anergy and the immunological synapses formed are phenotypically normal. We are performing live cell imaging experiments to characterize potential differences that occur in synapse formation and molecular recruitment to the synapse during the induction phase of anergy.
MICB 410 - Immunology
MICB 411 - Immunology Lab
MICB 502 - Advanced Immunology
MICB 495/595 - Principles of Light Microscopy
B.A. University of La Verne, La Verne, CA., 1987
M.S. California State Polytechnic University, Pomona, 1992
Ph.D. Oregon Health & Science University, Portland, OR, 2001
American Association of Immunologists
University of Montana Center for Environmental Health Sciences
Scientific Director, University of Montana Molecular Histology and Fluorescence Imaging Core Facility
UM Interdepartmental Immunology Graduate Degree Track
UM DBS Integrated Microbiology and Biochemistry Graduate Program
Osborne, D.G. and Wetzel, S.A. (2012) Trogocytosis leads to sustained signaling in CD4+ T cells. Journal of Immunology (in press)
Doherty, M., Osborne, D.G., Browning, D.B., Parker, D.C. Wetzel, S.A. (2010) Anergic CD4+ T cells form mature immunological synapses with enhanced accumulation of c-Cbl and Cbl-b. Journal of Immunology 184:3598-3608. PMCID: PMC2843782
Thauland, T.J.; Y. Koguchi, R.Varma, S.A. Wetzel, M.L. Dustin, and D.C. Parker. (2008). Th1 and Th2 cells fom morphologically distinct immunological synapses . The Journal of Immunology, 181:393-9
Blake, D.J.; Wetzel, S.A.; Jean C Pfau, J.C. (2008) Autoantibodies from mice exposed to Libby amphibole asbestos bind SSA/Ro52-enriched apoptotic blebs of murine macrophages. Toxicology, 246:172-9
Scott A. Wetzel and D.C. Parker. (2006) MHC transfer from APC to T cells following antigen recognition. Critical Reviews in Immunology. 26:1-21
Tara J. Dillon, K.D.Carey, S.A. Wetzel, D.C. Parker, P.J.S. Stork. (2005). Regulation of the Small GTPase Rap1 and Extracellular Signal-Regulated Kinases by the Costimulatory Molecule CTLA-4. Molecular Cell Biology, 25(10):4117-4128
Scott A. Wetzel, T. W. McKeithan, D.C. Parker. (2005). Peptide-specific intercellular transfer of MHC class II to CD4+ T cells directly from the immunological synapse upon cellular dissociation. Journal of Immunology. 174(1): 80-9
Tara J. Dillon, Vladimir Karpitski, Scott A. Wetzel, David C. Parker, Andrey S. Shaw, and Philip J. S. Stork (2003). Ectopic B-Raf expression enhances extracellular signal-regulated kinase (ERK) Signaling in T cells and prevents antigen presenting cell-induced anergy J. Biol. Chem. , 278:35940.
Wetzel, S.A. ; McKeithan, T.W.; Parker D.C. (2002) Live Cell Dynamics and the Role of Costimulation in Immunological Synapse Formation. Journal of Immunology. 169(11):6092
Sperry P.J.; Cua D.J.; Wetzel S.A.; Adler-Moore, J.A. (1998) Antimicrobial activity of AmBisome and non-liposomal Amphotericin B following uptake of Candida glabrata by murine epidermal Langerhans cells. Medical Mycology 36(3):135 - 141
Primus, F.J.; Finch, M.D.; Wetzel, S.A.; Masci, A.M.; Schlom, J.; Kashmiri, S.V.S. (1994) Monoclonal Antibody Gene Transfer: Implications for Tumor - Specific Cell - Mediated Cytotoxicity. Annals of the New York Academy of Science. 716: 154 - 166