T lymphocytes develop from a common lymphoid progenitor in the bone marrow that also gives rise to B lymphocytes, but those progeny destined to give rise to T cells leave the bone marrow and migrate to the thymus (see Fig. 7.2). This is the reason they are called thymus-dependent (T) lymphocytes or T cells.

Where does T cell development occur?

The thymus is the primary site of T cell development, where progenitors from the bone marrow lacking CD4⁺ and CD8⁺ coreceptor expression undergo T cell receptor (TCR) rearrangement to generate CD4⁺CD8⁺ double positive (DP) thymocytes.

How does T cells develop in human body?

Lymphoid progenitors which have developed from hematopoietic stem cells in the bone marrow migrate to the thymus to complete their antigen-independent maturation into functional T cells . In the thymus, T cells develop their specific T cell markers, including TCR, CD3, CD4 or CD8, and CD2.