DNA Methylation And In Vitro Induction of Cytotoxic CD4+ T-cells

Abstract

Cytotoxic CD4+ T-cells (CD4+ CTLs) have been observed in various disease contexts and more prevalently in chronic inflammatory diseases. Ranging from autoimmunity to severe acute and chronic viral infection to cancers, CD4+ CTLs are represented in multiple conditions with an unknown effect. However, the induction mechanism and progenitors of CD4+ CTLs have yet to be defined. Herein, I explore the potential mechanisms by which CD4+ CTLs may arise and develop a system to induce CD4+ CTLs in vitro. Induction of CD4+ CTLs has been observed in a diverse set of chronic inflammatory environments, primarily characterized by type 1 inflammatory environment. Type 1 inflammatory environments traditionally arise during the immune system’s response to intracellular pathogens, leading to the induction of cytotoxic CD8+ T-cells (CD8+ CTL) and recruitment of innate immune cells such as macrophages, natural killer cells, monocytes, and others. In particular, the inflammatory milieu of chronic inflammatory environments leads to a prolonged state of antigen exposure, costimulation, and cytokine signaling for both CD4+ and CD8+ T-cells. The combination of protracted antigen, co-stimulation, and cytokine signaling leads to (1) potential CD8+ T-cell exhaustion and (2) the potential induction of CD4+ CTLs, among a multitude of other effects. In chronic inflammatory diseases, the presence of CD4+ CTLs has been observed; however, it has not been elucidated whether the CD4+ CTLs are causative or correlative of the chronic inflammatory environment. The ongoing expansion of disease states in which CD4+ CTLs are recognized underscores the importance of understanding the mechanisms by which CD4+ CTLs arise. Developing a robust and efficient system to de-convolute the necessary signals in CD4+ CTL induction serves as an initial step in understanding a novel cell type and the signals required for cell state changes. Expansion of knowledge on this subject helps to improve our understanding of the cells that exist and function within multiple disease states. By investigating the epigenetic and transcriptomic landscape of CD4+ T-cells as they transition to CD4+ CTLs, we aim to define potential factors important for CD4+ CTL induction and maintenance. In all, we aim to understand CD4+ CTL biology by developing an in vitro induction system and, further, by manipulating the methylation infrastructure of CD4+ CTLs as they progress through the induction process. Specifically, controlling the enzymes involved in the transition between DNA methylation states will allow us to identify the critical methylation enzymes that allow for distinct cell state transitions to a CD4+ CTL state.