Lymphocytes that are self reactive will be deleted

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Unformatted text preview: te will express a different receptor on its surface. Each lymphocyte only expresses a single specific receptor, each is mono- specific. Because this occurs randomly in the thymus and bone marrow, generated randomly from the assembly of gene segments. Many, many gene segments that can be spliced together to make a receptor. Totally independent process, no antigen involved. Just randomly. The immune system is generating millions of the cells, each with a unique specificity, hoping that some of them will be useful in recognizing pathogen. Problem: could generate receptors that recognize self. First thing that immune system has to do (in bone marrow and thymus) and eliminate any that are self- reactive. 99.9% of lymphocytes are deleted because receptors are self reactive. Cells that eventually exit the thymus and bone marrow should be purged of self reactivity, mostly. The lymphocytes that survive circulate through blood, lymph, back to blood, looking for a dendritic cell that presents an antigen their receptors recognize. If don’t recognize, they are replaced with different specificities. Each lymphocyte has a specificity of receptor. If that receptor is able to recognize a pathogen peptide on the surface of an antigen presenting cell, the result will be activation. The clonal population of that lymphocyte will have identical receptors. Lymphocytes that are self reactive will be deleted from the repertoire. These are receptors. Left is the B cell receptor for an antigen, otherwise known a antibody. The one on the right is T cell receptor...
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