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Author ORCID Identifier


Campus-Only Access for Five (5) Years

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program

Animal Biotechnology & Biomedical Sciences

Year Degree Awarded


Month Degree Awarded


First Advisor

Barbara A. Osborne

Subject Categories



Notch, a conserved protein among different species regulates different stages of development of multiple cell types. The activated form of Notch is the cleaved intracellular domain of the Notch receptor which can migrate to the nucleus and initiate transcription of target genes. In T cells Notch modulates different developmental processes, proliferation, and differentiation. Notch ligands, on the other hand, have been shown to have a positive or negative impact on Notch signaling, by trans-activation or cis-inhibition. When the receptor and ligand are on two different cells and interact in a trans manner, this sends an activation signal for Notch. When they are present and interact on the same cell surface, an inhibitory signal is sent. Pathogen dependent Notch ligand expression has been defined on the APCs which are capable of tailoring CD4 T cell responses towards the pathogen by regulating helper T cell differentiation. In contrary, there are studies showing Notch activation in T cells is independent of interaction with Notch ligand. Overall the function of Notch ligands in regulating Notch activation in T cells remains obscure. Thus, in this study we demonstrate that mature CD4 T cells are capable of expressing Notch ligands on their surface very early upon viii activation with soluble antibodies against CD3 and CD28. Additionally, we provide evidence to show that Notch ligand expression on the CD4 T cells is solely regulated by CD28 signaling and TCR (CD3) signal strength acts as an inhibitory signal for ligand expression, in contrast to Notch, where CD3 is the signal regulating Notch activation. By using decoys, mimicking the Notch extracellular domain, we demonstrated that these ligands DLL1, DLL4, and JAG1, expressed on the T cells, can cis-interact with the Notch receptor and inhibit activated Notch. Thus our data indicate a novel mechanism of the regulation Notch ligand expression on CD4 T cells and its impact on activated Notch.