mcb150-fa10-mt2-Nilabh Shastri-soln

mcb150-fa10-mt2-Nilabh Shastri-soln - (10) Q. In T cells,...

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Point Total ……………./40 (10) Q. In T cells, transcription factors such as NF-AT translate antigen recognition on the surface into transcription of specific genes. In which cellular location is the NF-AT protein normally found in resting T cells? What is the role of the NF-AT protein in the induction of IL-2 secretion by activated T cells. Why is the function of NFAT sensitive to intracellular calcium concentration? In resting cells, the NF-AT protein is found in a phosphorylated state in the cytoplasm. Upon activation, the NF- AT protein is dephosphorylated by calcineurin phosphatase, translocated into the nucleus and together with other transcription factors, notably, AP1 (c-fos/c-jun), it can cause transcription of the IL-2 gene. Function of NF-AT is sensitive to calcium concentrations because the activity of the calcineurin phosphatase, necessary for its dephosphorylation, and translocation into the nucleus, is affected by calcium via calmodulin. (10) Q: Briefly describe why the drugs cyclosporin A (or FK506) are useful in inhibiting rejection of transplanted organs obtained from completely unrelated donors. Your answer must specify the effector cells that recognize appropriate ligands on the foreign transplant and the molecules that are directly affected by these drugs. Both CD4 and CD8 T cells recognize foreign peptide/MHC class II and peptide/MHC class I complexes expressed by donor cells (alloreactivity). Cyclosporin blocks the phosphatase activity of calcineurin. NF-AT can thus no longer be de-phosphorylated and cannot be translocated into the nucleus and cells cannot produce IL-2 or IL-2 receptor. Q. (6) The αβ TCR has only one isotype (constant region) in contrast to antibodies which have many. Speculate on a possible reason why the αβ TCR does not have other isotypes. Ab isotypes allow multiple effector functions in an antigen binding molecule. Maybe the TCR does not have to carry out multiple effector functions like Ab and therefore doesn’t need isotypes . OR a single TCR constant regions could be somehow capable of providing multiple “Fc-like” functions by associating with different signalling molecules. OR TCR only signals ligand occupancy and multiple functions may arise due to different functional states of the T cell. Note: Just saying secretion vs membrane bound only got partial credit. Needed to talk about functional consequences of only being membrane bound or getting secreted. (14) Q . To study antigen processing pathways, you obtain mutant mice from a colleague who has generated them on the C57BL/6 (B6, H-2 b ) background. However, when you get the mice, you discover that the mouse cages had no labels and you are required to distinguish the normal B6 from the mutant mouse strain. You stain all white blood cells of each strain with the anti-A b and anti-K b
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This note was uploaded on 09/14/2011 for the course MCB 58180 taught by Professor Kuriyan during the Spring '11 term at University of California, Berkeley.

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mcb150-fa10-mt2-Nilabh Shastri-soln - (10) Q. In T cells,...

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