Lecture 21D: T Lymphocytes (T Cells) PDF
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Summary
This lecture document provides a detailed overview of T lymphocytes (T cells), focusing on their life cycle, stages, and functions. It discusses T-cell activation, highlighting their roles in both specific and non-specific immune responses. This document also touches on the importance of the MHC complex in T-cell function.
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T Lymphocytes (T Cells) Life history involves three stages and three anatomical stations in the body – Born in the red bone marrow Dorn – Go to school in the thymus school – Deployed to the lymphatic organs work - - - T Lymphocytes (T Cells) University of the Thymus & veryacteent In fetal – Thymosin...
T Lymphocytes (T Cells) Life history involves three stages and three anatomical stations in the body – Born in the red bone marrow Dorn – Go to school in the thymus school – Deployed to the lymphatic organs work - - - T Lymphocytes (T Cells) University of the Thymus & veryacteent In fetal – Thymosins stimulate maturing T cells to develop surface antigen receptors → immunocompetent receptor Capable of recognizing antigens presented to them by APCs Teacher& – Reticuloendothelial (RE) cells in the thymus test T cells by presenting self-antigens to them (the final exam!) likeOdosn Two ways to fail the test: > pass – Inability to recognize the RE cells, especially their MHC go to antigens (positive selection) » Would be incapable of recognizing a foreign attack fail Selection on the body failed test fail – Reacting to the self-antigen (negative selection) » T cells would attack one’s own tissues -failed notieener - Selection T cells To to be able recognize MHC Selection - test test T Lymphocytes (T Cells) T Lymphocytes (T Cells) 2% of the T cells that reach the thymus leave as immunocompetent T cells (They passed the final!!) Deployment – Naive T cells leave thymus and colonize lymphatic tissues and organs everywhere in the body Cells of Cellular Immunity Cytotoxic T (TC) cells: killer T cells (T8, CD8, or CD8+) – “Effectors” of cellular immunity; carry out attack Helper T (TH) cells (T4, CD4, CD4+) – Promote TC cell and B cell action and nonspecific resistance Regulatory T (TR) cells: T-regs – Inhibit multiplication and cytokine secretion by other T cells; limit immune response Memory T (TM) cells – Responsible for memory in cellular immunity Cellular Immunity Cellular (cell-mediated) immunity – A form of specific defense in which the T lymphocytes directly attack and destroy diseased or foreign cells – The immune system remembers the antigens and prevents them from causing disease in the future – Antigen presenting cells required Antigen Presentation Antigen presentation – APC encounters & processes an antigen – Migrates to nearest lymph node and presents it to the T cells – T cells see antigen displayed on an MHC protein → immune response MHC-I → Cytotoxic T cells MHC-II → Helper T cells T cell activation – T cell binds to MHC displaying an epitope that it recognizes – Co-stimulation occurs – Clonal selection Effector cells Memory cells MHC Cytotoxic T Cells Helper T Cells
