T lymphocytes are a crucial component of cellular defense, playing a vital role in immune response. These cells are derived from hematopoietic stem cells located in the bone marrow, and the thymus is a critical organ for their development. During the maturation process in the thymus, the cells acquire specific surface receptor molecules such as TCR (T cell antigen receptor) and CD (cluster of differentiation ) that enable them to become T Lymphocytes capable of generating a specific immune response. The cellular components that exist on the surface of cells, known as cell surface molecules, include CD4, CD8, CD25, and CD44. Upon arrival in the thymus, immature T cells are referred to as early T cell precursors and lack the surface molecules CD4 and CD8. However, as they progress through various developmental stages, they are activated by cytokines and ligands produced by thymic epithelial cells (TEC), and display the surface molecules CD4, CD8, CD25, and CD44. These surface molecules also engage with the MHC (Major Histocompatibility Complex ) molecules and undergo positive and negative selection, ensuring that only mature T lymphocytes, which complete their development in the thymus, are released into peripheral lymphoid organs via the circulation.