- The primary site for the maturation of T lymphocytes is the thymus.
- T lymphocytes, also known as T cells, originate from hematopoietic stem cells in the bone marrow, but they do not fully mature there. Instead, immature T cells migrate to the thymus gland, where they undergo a critical process of differentiation and selection.

- During this maturation process in the thymus, T cells are educated to recognize foreign antigens presented by major histocompatibility complex (MHC) molecules while becoming tolerant to the body's own tissues.
- This selection ensures that only T cells with appropriate antigen specificity survive, preventing autoimmune responses.
- The bone marrow is the site of origin, but it is the thymus that provides the necessary environment for T cell maturation.

- In contrast, the spleen and lymph nodes serve primarily as secondary lymphoid organs where mature lymphocytes, including T cells and B cells, become activated upon encountering antigens, but they are not sites of primary maturation.

Summary:
- T cells originate in bone marrow.
- Primary maturation and selection of T cells occur in the thymus.
- Spleen and lymph nodes are involved in activation, not maturation.

Reference: Immunology: A Short Course, 7th Edition, Chapter 3, p. 65