لخّصلي

1.This exposure aids in the ultimate selection of T cells possessing the proper functional avidity and TCR specificity.The positive selection: which takes place in the thymic cortex, guarantees that T cells produce a functioning T cell receptor (TCR) that can identify antigens that are presented by major histocompatibility complex (MHC) molecules.Negative Selection: Also found in the cortex, negative selection removes thymocytes possessing TCRs that firmly attach to MHC-presented self-antigens.Thymocytes that are immature and do not express a TCR die.2.

1. 
   

   The positive selection: which takes place in the thymic cortex, guarantees that T cells produce a functioning T cell receptor (TCR) that can identify antigens that are presented by major histocompatibility complex (MHC) molecules. Thymocytes that are immature and do not express a TCR die. Interactions between thymic epithelial cells or dendritic cells that express self-peptides on MHC molecules and growing thymocytes drive positive selection.

   
   


2. 
   

   Negative Selection: Also found in the cortex, negative selection removes thymocytes possessing TCRs that firmly attach to MHC-presented self-antigens. This procedure aids in preventing the growth of autoreactive T cells, which have the potential to induce autoimmune illnesses. Negative selection causes thymocytes to either die out or develop into regulatory

   
   


3. 
   

   Medulla Maturation: Thymocytes that make it through both positive and negative selection move to the medulla, where they undergo additional maturation. They come into contact with dendritic cells and medullary thymic epithelial cells in the medulla, which offer a variety of self-antigens. This exposure aids in the ultimate selection of T cells possessing the proper functional avidity and TCR specificity.