TL:DR – T cells do not develop properly in mice that have had their thymus gland surgically removed (thymectomized) before birth or in early neonatal life.
The thymus is an essential lymphoid organ required for T cell development and maturation. Thymectomy experiments in mice demonstrated this critical role:
In mice thymectomized as newborns:
- The mice failed to develop mature T cells in the periphery
- They lacked T cell populations in the spleen, lymph nodes, blood
- However, their B cell populations were largely normal
This showed that the thymus is indispensable for T cell differentiation and the establishment of a functional T cell repertoire.
The thymus provides the specialized microenvironment for several key T cell developmental processes:
- Rearrangement and expression of functional T cell receptors (TCRs)
- Positive and negative selection of self-MHC restricted, non-autoreactive T cells
- Commitment to the CD4 or CD8 lineages
Without a thymus, precursor T cells remain blocked at an immature stage and cannot undergo the selection processes that shape the mature self-MHC restricted, self-tolerant T cell repertoire.
However, some T cell differentiation can still occur in thymectomized mice, but the resulting T cells tend to be oligoclonal, autoreactive, and non-functional.
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Source: Claude 3 Sonnet response prompted and edited by Joel Graff.
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