13. What happens to autoreactive cells that escape the thymus? A. They attack se
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13. What happens to autoreactive cells that escape the thymus? A. They attack self tissues. B. They can be rendered anergic. C.They negatively regulate other autoreactive cells. D. They require TCR-ligation and costimulation to be activated. E. All of the above 14. What is currently the best explanation for what determines whether a T cell develops into a CD8 T cell or a CD4 T cell? A. CD4/TCR coengagement suppresses CDS expression, and CD8/TCR coengagement suppresses CD4 expression. B. T cells randomly down-regulate CD4 or CD8, and only cells that still bind the appropriate MHC will get a strong enough signal to survive. C. CD4 or CD8 expression is determined by the strength and duration of the TCR/MHC interaction D. CD4 or CD8 expression is predestined in the bone marrow. E. Only aß T cells express CDs. 15. Which of the following are characteristics of apoptosis? A. Membrane blebbing B. swelling of the cytoplasm C. Increased metabolism D. Release of cellular contents into the extracellular space E. All of the above 16. Tasos have been shown to be protective against which of the following conditions? A. Inflammatory bowel disease B. HIV disease C. Influenza infection D. MRSA E. MalariaExplanation / Answer
13 E they exit from the thymus and then final maturation.but not all self antigens are expressed in the thymus.
14 c The kinetic model has the greatest experimental support.
15 A Apoptosis is programmed cell death.it requires ATP.plasma membrane remains intact .plasmamembrane blebs with organelle and cells break into apototic bodies.
16 A Transcription factor is not characteristic of T-celll activation.Because TREG s can develop from autoreactive cells.
17 E
18 D Tcellactivation require antigen being displayed in the contact of an APC and interaction between c-stimulatory molecules on the APC and on the Tcell .T cell activity is influenced by cytokines.
19T cells are activated through antigen presentation.Signal 1 initiates Tcell proliferation.it contains a TCR,zeta chain,and CD4 or CD8.Binding of MHC/oeptide to the TCR initiates signal 1..Co-stimulatory molecules provide signal 2 .it is generated by the binding of CD 28 on the Tcell to B7 molecules ie CD 80,CD 86 on the APC.
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