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

One of the most important genes to be transcribed

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One of the most important genes to be transcribed codes for the cytokine IL-2 Activation of T cell by professional APC initiates a program of differentiation controlled by the cytokine IL-2. A burst cell division Acquisition of effector function IL-2 is synthesized and secreted by activated T cells . IL-2 binds IL-2 receptors of T cell to drive clonal expansion of the activated cell IL-2 is one of a number of cytokines produced by activated and effector T cells to control the development differentiation of cells in the immune response. Slide 102 ↓ | IL-2 production requires both the signal delivered through the TCR:co- receptor complex and the co-stimulatory signal delivered through CD28. Signals through the TCR:CD3 complex activate NFAT activate transcription of the IL-2 gene (IL-2 mRNA is inherently unstable). Co-stimulation (CD28:B7) stabilizes the IL-2 mRNA which causes an increase in the synthesis of IL-2 by T cells (20-30X). Co-stimulation also activates other transcription factors that stimulate the transcription of the IL-2 gene (3X). Principal effect of co-stimulation is to increase synthesis of IL-2 by 100 fold . Slides 103-104 | Activated T cells secrete and respond to IL-2 Slide 103 ↓ | Naïve T cells express the low-affinity receptor for IL-2 which consists of and ? chains Activation of a naïve T cell by the recognition of a peptide:MHC complex accompanied by co-stimulation induces the synthesis and secretion of IL-2 and the synthesis of the IL-2 receptor chain Cell enters the first phase ( G1 ) of cell-division cycle
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chain combines with the and ? chains to make a high-affinity receptor for IL-2 IL-2 binds to the IL-2 receptor producing an intracellular signal that promotes T-cell proliferation Slide 104 ↓ | Slides 105-106 | Antigen recognition without co-stimulation leads to a nonresponsive T cell Slide 105 ↓ | When a TCR on a mature naïve T cell binds to a peptide:MHC complex on an APC that does not express the co-stimulatory molecule B7 the T cell becomes nonresponsive or anergic and cannot be activated with subsequent antigen encounter.
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Slide 106 ↓ | Some mature naïve T cells may be specific for self-proteins expressed by cells not found in the thymus. These T cells will not be activated because the cells expressing these self antigens will not express the co-stimulatory molecule, B7 . A mature, naïve T cell that binds a self-peptide:MHC complex on a cell without B7 does not receive a co-stimulatory signal and undergoes anergy. Anergic T-cells don’t make IL-2 no proliferation or differentiation Anergic T cells can never be stimulated to proliferate or differentiate. This process induces tolerance in the mature T cell repertoire . Slides 107-108 | Studying Ab and T-cell responses in lab animals Slide 107 ↓ | Immunization of protein antigen alone rarely induces an immune response.
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  • Winter '17
  • T Cells, T Cell, development of T cells

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