KARA - Immunology Exam 4 - Chapter 7 & 8.docx

Effector t cells can interact with target cells

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Effector T cells can interact with target cells expressing lower levels of ICAM-1 and LFA-3. Interactions of effector T cell with target cells is short-lived UNLESS the TCR is engaged by specific antigen . The interaction leads to a conformational change in LFA-1 that strengthens the adhesion between the two cells. Slide 126 | Example of Resting CD4 T cell Resting naïve T cells express L- selectin (for homing to LN) and relatively low levels of CD2 & LFA-1 (lymphocyte function –associated antigen-1 on surface of lymphocytes) adhesion molecules When activated , L-selectin expression stops & increased amounts of integrin LFA-1 are made
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Slide 127 | Example of Activated CD4 T cell Integrin VLA-4 is expressed ( homing receptor for vascular endothelium at sites of inflammation ) and guides activated T cells to the infection site . Activated T cells have more surface CD2 which leads to increased adhesion to target cells. Slide 128 | Example of CD4 T cell increased sensitivity Alternative splicing of RNA made from the CD45 genes causes activated T cells to express the CD45RO isoforms that associates with the TCR and CD4 …this change makes the T cell more sensitive to stimulation by lower concentrations of peptide:MHC complexes.
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Slide 129 | Changes in adhesion molecule expression = changes in migration patterns Changes in the adhesion molecule expression of activated effector T cells versus resting naïve T cells also results in different patterns of migration . Without the expression of L-selectin effector T cells no longer recirculate through lymph nodes by leaving the blood through HEVs. Effector T cells instead express VLA-4 which enables binding to endothelial cells of blood vessels in infected/ inflamed tissues – where their effector function is needed. VLA-4 binds to the cell adhesion molecule VCAM-1 which is selectively expressed on the endothelium of blood vessels in inflamed tissue. Slide 130 | Integrin VLA-4 enables effector T cells to home to inflamed tissue T cell migration or antigen presentation Recruitment of effectors T cells into inflamed or infected tissues
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Slides 131-132 | Effector T-cell functions are performed by cytokines and cytotoxins Slide 131 ↓ | Molecules that carry out T cell effector functions: Cytokines , which alter the behavior of target cells. All effector T cells produce cytokines (just different types and in different combinations ). Cytotoxins , secreted cytotoxic proteins used to kill target cells. Cytotoxins are specialized products of cytotoxic CD8 T cells . Slide 132 ↓ | Slide 133 | Secreted cytokines Secreted cytokines and related membrane-bound proteins that act through cell-surface receptors generally to induce changes in gene expression within target cells .
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  • Winter '17
  • GREGORYWEIGEL
  • T Cells, T Cell, development of T cells

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