Figure 1.

Neonatal and adult T cells have different origins and functions. This figure depicts the layered immune system model for CD4⁺ and CD8⁺ T cells. Unlike adult T cells, neonatal T cells are derived from fetal hematopoietic stem cells, exhibit shorter and more restricted T cell receptors in the absence of TdT, and undergo higher rates of homeostatic proliferation in the periphery. Following stimulation, neonatal T cells more quickly differentiate into effector or regulatory T cells than their adult counterparts, albeit at the expense of forming long-lived memory cells. Abbreviation: TCR, T cell receptor.