To date, our best tools for assessing the frequency and affinity of CD4+ T cells have been peptide:MHC (pMHC) tetramers or functional assays;neither of which effectively identify all of the responding cells to a particular antigen. This is in contrast to CD8+ T cells where these techniques prove more accurate. Generally, pMHC tetramers for class II antigens are difficult to produce and identify a small percentage of responding CD4+ T cells especially when antigen is derived from self proteins. The reason for this is that tetramer is based on affinity and if affinity is too low, then the tetramer is of limited use in assessing the response Functional responses also underestimate the number of antigen reactive CD4+ T cells. In the case of responses directed against myelin antigens for instance, the effector cytokine response is often determined using strong pharmacologic agents such as PMA and ionomycin, which hammer the T cell signaling cascade and may have little relevance to the cytokines being produced in response to antigen itself. To better assess the range of responding CD4+ T cells, we have begun to use micropipette based affinity assay. We report here a major advancement in assessment in the frequency and affinity of CD4+ T cells directed against myelin or viral antigens. Therefore for the first time, it is possible to track the range of affinities of a CD4+ T cells response during disease progression. Our preliminary findings have led to the following central hypothesis that the CD4+ T cell affinity profile directly impacts disease outcome and immune mediated tissue damage in the CNS.
Three specific aims are proposed to test this hypothesis focused on CD4+ T cells specific for self antigen myelin oligodendrocyte glycoprotein and pathogen associated lymphocytic choriomeningitis virus antigens.
Aim 1 - Identify the affinity of CD4+ T cells over the course of chronic autoimmune disease and viral infection.
Aim 2 - Define the connection between T cell affinity and effector phenotype.
Aim 3 - Establish the contribution of high versus low affinity T cells in response to antigens found in the CNS.

Public Health Relevance

CD4+ T cells play a major role in the pathogenesis of autoimmune responses such as multiple sclerosis (MS) and are critical for proper response to chronic viral infections. The overall goal of this grant is to define the range of T cell affinities for myelin and viral antigens in the central nervous system (CNS. The proposed studies apply a novel means for assessing the affinity if the responding T cell response in the murine EAE and LCMV models, but our results should be rapidly transferable to patients. Therefore, our findings are highly relevant to human health and will prove to be a valuable asset for assessing disease prognosis and for the development of effective treatments.

National Institute of Health (NIH)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Utz, Ursula
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Emory University
Schools of Medicine
United States
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Kersh, Anna E; Edwards, Lindsay J; Evavold, Brian D (2014) Progression of relapsing-remitting demyelinating disease does not require increased TCR affinity or epitope spread. J Immunol 193:4429-38
Zhu, Cheng; Jiang, Ning; Huang, Jun et al. (2013) Insights from in situ analysis of TCR-pMHC recognition: response of an interaction network. Immunol Rev 251:49-64
Rosenthal, Kristen M; Edwards, Lindsay J; Sabatino Jr, Joseph J et al. (2012) Low 2-dimensional CD4 T cell receptor affinity for myelin sets in motion delayed response kinetics. PLoS One 7:e32562
Edwards, Lindsay J; Evavold, Brian D (2011) T cell recognition of weak ligands: roles of signaling, receptor number, and affinity. Immunol Res 50:39-48
Sabatino Jr, Joseph J; Huang, Jun; Zhu, Cheng et al. (2011) High prevalence of low affinity peptide-MHC II tetramer-negative effectors during polyclonal CD4+ T cell responses. J Exp Med 208:81-90