Browsing by Subject "autoantibody"

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    Novel insights into Addison's disease in dogs
    (2023-05) Treeful, Amy
    Addison’s disease is a dangerous hormone deficiency found in humans and dogs. Studies in humans support a complex autoimmune etiology, however evidence in studies in dogs is sparse. The work summarized in this dissertation was conducted to evaluate contributions from each of the three main types of risk factors of a complex autoimmune disease to developing AD in dogs; immunological, genetic, and environmental risk factors. Firstly, the immunological study tested the hypothesis that similar to humans with AD, dogs with AD have anti-adrenocortical autoantibodies. Several different immunoassays were performed to screen IgGs from three dog breeds predisposed to AD (Standard Poodles, Portuguese Water Dogs, and English Cocker Spaniels) for autoantibodies to adrenal antigens. Two different, mostly non-overlapping positive results were found in Western blots; IgGs from dogs with AD often had antibodies to a 42kDa band or to a 75kDa band. However, inconsistent replicability made it difficult to form definitive conclusions. Results from other immunoassays were also either inconclusive or negative. Secondly, the genetic study tested the hypothesis that certain MHC Class II genes and/or haplotypes are associated with AD in dogs from a breed with elevated risk of developing AD, Standard Poodles. Sanger sequencing of exon 2 of MHC class II haplotypes allowed for the identification of two sex-specific associations. Thirdly, an online survey study was used to compare the frequencies of certain environmental exposures and lifestyle factors between dogs with and without AD in a study cohort consisting of dogs from two high risk breeds, Standard Poodles and Portuguese Water Dogs. The variable with the highest effect size associated with AD was spay (odds ratio 2.5, 95% CI [1.4-3.5]) and neutering (odds ratio 6.0, 95% CI [2.6-13.9]). A lack of consistent positive results in the immunology study can be interpreted several different ways; 1) technical issues prevented autoantibodies from being detected, 2) AD in dogs from the breeds in this study is not immune-mediated, or 3) AD is primarily T-cell mediated and there are no autoantibodies. Results from the genetic and survey study suggest that sex hormones play a role in influencing susceptibility to AD in dogs. However, these results are correlational and future studies are needed to determine whether these associations can be explained by molecular mechanisms.
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    Programmed death-1 regulates islet-specific lymphocytes in type 1 diabetes
    (2018-12) Martinov, Tijana
    Programmed death-1 (PD-1) is a T cell inhibitory receptor important for tolerance maintenance. PD-1 is highly expressed on chronically stimulated T cells, such as those specific for persistent viral or tumor antigens. PD-1 pathway blockade revolutionized cancer therapy in recent years. While response rates are higher than with chemotherapy, not all patients respond, and some develop autoimmune-like symptoms, or even overt autoimmunity. Herein, I sought to understand how the PD-1 pathway regulated islet-specific CD4+ T cells during type 1 diabetes (T1D) progression in non-obese diabetic (NOD) mice. Since insulin itself is one of the main antigens driving T1D, we developed insulin peptide:MHCII tetramer reagents to track insulin-reactive CD4+ T cells. Insulin-specific CD4+ T cells that expressed the most PD-1 also had the highest affinity for self, suggesting that PD-1 preferentially regulated those cells with the highest autoimmune potential. In NOD mice, the majority of insulin-specific CD4+ T cells had an anergic (tolerant) phenotype, but surprisingly, PD-1 blockade did not override the anergy program. These findings suggested that the differentiation state of the CD4+ T cell pre-determine its susceptibility to PD-1 blockade. Autoantibody production is a hallmark of autoimmunity, and has also been reported in patients treated with PD-1 blockade, suggesting that PD-1 might regulate this process. Autoantibody production results from B cell:CD4+ T cell interactions in the germinal center of the lymph node. The dynamics and regulation of the germinal center in spontaneous autoimmunity and after PD-1 blockade are not well understood, primarily due to an inability to track self-specific lymphocytes. To bridge this knowledge gap, we used tetramers to phenotype islet-specific CD4+ T cells and B cells in mice. PD-1- or PD-L1-deficient mice, as well as NOD mice treated with anti-PD-1, had increased insulin autoantibodies, as well as increased insulin-specific T follicular helper CD4+ T cells and germinal center B cells compared to controls. This increase was dependent on CD4+ T cell-intrinsic PD-1 signaling and relied on peptide:MHCII recognition. Taken together, my thesis work provides a mechanistic explanation for autoantibody onset following PD-1 blockade in the clinic, and has important implications for cancer immunotherapy and autoimmunity.