T-cell maturation and its acquisition of the repertory reactive to foreign antigens in the thymus is one of the important topics in recent immunology. T cells are mainly categorized into two subtypes, helper and killer cells. Most of the helper T cells express CD4 antigens on their cellular surface, while killer T cells express CD8 antigens. These two surface antigens play an important role for the adherence to the target cells in helping the T-cell receptor for antigens (TCR) recognize major histocompatibility complex (MHC) antigens. Recently, differentiation of T cells within the thymus has been clarified by using these two surface marker antigens. Bone marrow-derived pre-T cells do not express either CD4 nor CD8 antigen. They express CD8 antigen first, but at this time they still do not express TCR/CD3 antigen complex and are regarded as an immature type. Immature CD8+ cells next express CD4 antigen and the TCR/CD3 antigen complex. This population of the thymocytes (CD4+8+) are thought to receive both negative and positive selections. CD4+8+ cells, which escaped from the clonal deletion, differentiate into mature single-positive cells (either CD4+8- or CD4-8+ cells). This sequential maturation of T cells requires the aid of thymic stromal cells.
KeywordsMajor Histocompatibility Complex Mixed Lymphocyte Culture Killer Assay Peripheral Lymphoid Organ Thymic Stromal Cell
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- 1.Sasaki M, Yoshida MC, Kagami K, Takeichi N, Kobayashi H, Dempo K, Mori M (1985) Spontaneous hepatitis in an inbred strain of Long-Evans rats. Rat News Lett 14:4–6.Google Scholar