Immunology and Microbiology
Department of Microbiology and Physiological Systems
First Thesis Advisor
Samuel Behar, MD, PhD
tuberculosis, TB, immunity, CD8 T cells, CD4 T cell help, T cell exhaustion
Tuberculosis (TB), a transmissible disease caused by Mycobacterium tuberculosis (Mtb), is a global health threat. To design an effective vaccine, we need to better understand how different elements of our immune system collaborate to fight against Mtb. CD4 T cells are crucial in protective immunity to Mtb because they produce cytokines including interferon-γ. In contrast, CD8 T cells are thought to play a modest role. Whether CD4 T cells act as “helper” cells to promote optimal CD8 T cell responses during TB is unknown. We argue CD8 T cells’ role are likely underestimated because CD8 T cell functions are compromised without CD4 T cells. Here, using two independent models, I show that CD4 T cell help promotes CD8 T cell effector functions and prevents CD8 T cell exhaustion. I demonstrate CD4 and CD8 T cells synergistically enhance the survival of infected mice. Purified helped, but not helpless, CD8 T cells effectively restrict intracellular Mtb growth. Thus, CD4 T cell help is indispensable for generating protective CD8 T cell responses. In addition, I investigate the mechanisms of CD4 T cell help. Signals from CD4 T cells, and signals relayed by antigen presenting cells collectively shape CD8 T cell responses. We infer that vaccines aimed for eliciting both CD4 and CD8 T cells, in which CD8 T cells are properly helped by CD4 T cells, are more likely to be successful.
Lu Y. (2021). The Role of CD4 T Cell Help in Effective CD8 T Cell Responses during Mycobacterium Tuberculosis Infection. Morningside Graduate School of Biomedical Sciences Dissertations and Theses. https://doi.org/10.13028/ve6s-c368. Retrieved from https://escholarship.umassmed.edu/gsbs_diss/1139
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