[Immunologic tolerance]

The thymus plays a major role in T-cell maturation. Non-mature, bone-marrow-derived T-lymphocytes differentiate in the thymus into functional helper and cytotoxic T-cells, which have undergone two types of selection events before they leave the thymus: The negative selection, that is the elimination of self-reactive T-cells, and the positive selection, which supports the survival of T-cells capable of recognizing foreign antigen together with self-major histocompatibility antigens. Induction of T-cell tolerance towards the self-antigen Mlsa as a model is mediated by the selective deletion of Mlsa-reactive T-cells in the cortical region of the thymus. This was demonstrated by histological and flow cytofluorometrical analysis with a T-cell receptor variable-region-specific monoclonal antibody.