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T-Lymphocyte
Aka: T-Lymphocyte, T-Cell, T-Cell Activation, T-Cell Surface Receptor, T-Helper Cell, Helper T-Cell, CD4+ Cell, T-Cytotoxic Cell, Cytotoxic T-Cell, CD8+ Cell
- See Also
- White Blood Cell (Leukocyte)
- Lymphocyte
- Immune System
- B-Lymphocyte (B Cell)
- Natural Killer Cell (NK cell)
- Definitions
- T-Lymphocytes (T-Cells)
- T-Cells are responsible Cell-Mediated Immunity
- T-Cells target Intracellular Pathogens (e.g. viruses and Intracellular Bacteria) and cancer cells
- Physiology
- T-Cells
- Derived in Bone Marrow
- Migrate to Thymus
- Maturation and Differentiation into two cell lines with different T-Cell Receptors (CD4 and CD8)
- Release into peripheral circulation
- T-Cell Surface Receptors and Accessory Molecules
- T-Cell Receptors (TCR)
- Bind the Antigen on the Antigen Presenting Cell (APC)
- Similar structure to Antibody
- Each chain (a, b, g or d) has a constant region (C) and a variable region (V)
- Variable region (V) on each chain forms Antigen binding site
- TCR Types (based on polypeptides ab or gd)
- TCR-alpha-beta (TCRab+)
- TCR gamma-delta (TCRgd+)
- Plasticity
- T-Cell Receptors (TCR) have variable regions whose genes may be rearranged
- Rearranging variable region genes allows for a reflex change in TCR binding target
- Similar mechanism to B-Cell Immunoglobulin Gene modification
- T-Cell Signal Transduction related Costimulatory Receptors (Allows for T-Cell Activation)
- CD3 and Zeta (Z) are part of T-Cell Receptor Complex (along with TCR)
- CD3 and Zeta (Z) are involved with signal transduction from T-Cell surface to inside of T-Cell
- T-Cell Receptors together with CD3 and Zeta (Z) are known as T-Cell Receptor Complex
- T-Cell Receptor Complex binds Peptide-MHC Complex as first signal in T-Cell Activation
- CD28
- Binds Ligand B7 (receptor found on APCs) as part of second signal in T-Cell Activation
- T-Cell Co-Receptors
- CD4 binds peptide/Antigen-MHC Class 2 complex on surface of Antigen Presenting Cells (APC)
- CD8 binds peptide/Antigen-MHC Class 1 complex on surface of Antigen Presenting Cells (APC)
- Adhesion Molecules (T Cell Surface Receptor proteins that bind Ligands on Antigen Presenting Cell)
- Lymphocyte Function Associated Antigen-1 or LFA-1
- Binds Ligands intracellular Adhesion Molecule 1-3 (ICAM 1-3)
- Cluster of Differentiation 2 (CD2)
- Binds Ligand LFA-3
- Cluster of Differentiation 44 (CD44)
- Binds Ligand Hyaluronate
- Naive T-Cell Activation

- T-Cell Receptor (TCR) binds to MHC-Antigen complex on Antigen Presenting Cells (APC)
- T-Cell Surface CD28 binds to B7 Ligand on Antigen Presenting Cell
- T-Cell Surface LFA-1 (Lymphocyte Function Associated Antigen) binds ICAM1 on Antigen Presenting Cells
- Interleukin-2 (IL2) produced by naive T Cells
- Stimulate T Cell proliferation
- Types: T-Cells
- Effector Cells
- T-Helper Cells (CD4+ Cells)
- Releases Interferon
- Stimulates Phagocytosis by Macrophages
- Activates Natural Killer Cells
- Suppresses viral replication
- Releases interleuken 2
- Promotes T-Cell proliferation (esp. memory cells)
- Promotes B-Cell proliferation (memory cells and plasma cells)
- T-Cytotoxic Cells (CD8+ Cells)
- Target and destroy tumor cells and virus-infected cells
- Other Cells
- Memory Cells
- Apoptosis of some cells not otherwise differentiated
- References
- Guyton and Hall (2006) Medical Physiology, p. 419-50
- Mahmoudi (2014) Immunology Made Ridiculously Simple, MedMaster, Miami, FL