Figure 2. Systemic changes in the immune system with aging, obesity, and dietary restriction.

T cell progenitors arise in the bone marrow and travel to the thymus where they develop into mature naïve T lymphocytes. Naïve T cells circulate through the bloodstream and secondary lymphoid organs. Systemic conditions like aging, obesity, and dietary restriction affect the immune system at each of these levels, impacting both anti-tumor and other immune responses. Aging- and obesity-associated changes lead to reduced T cell immunity, while dietary restriction-associated changes promote T cell responses. CLP, common lymphoid progenitor. SLO, secondary lymphoid organs. TCR, T cell receptor.