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. Author manuscript; available in PMC: 2023 Jul 1.
Published in final edited form as: Kidney Int. 2022 Apr 9;102(1):25–37. doi: 10.1016/j.kint.2022.02.035

Figure 1. αβT lymphocyte maturation and most common theories about the origin of DN T cells in periphery.

Figure 1.

The development of murine αβT cells in thymus physiologically includes DN stages 1–4 of thymocytes that are defined by the expression of CD44+ and CD25+. To describe the development of mature TCRαβ+ double negative (DN) T cells in periphery, there are five theories. According to theory 1 CD4+ or CD8+ down regulate their coreceptor in the periphery to become DN T cells 21,23 Theory 2 hypothesizes hematopoietic stem cells go directly from bone marrow and mature into DN T cells in the periphery.6,24 Theory 3 suggest that DN4 stage to DP transition in thymus was never completed and DN T cells traveled to periphery.25 Theory 4 suggests an alternate pathway through the thymus.6 According to theory 5, peripheral DN T cells are a pool of heterogenous cells with different origins. Peripheral DN T cells have been found in steady-state and diseased organ tissue.4 Of important note, stages of TCR γ and δ selection is currently unclear, however, it is known their arrangement occurs prior to TCR α and β selection during the DN stage.17,20