Bi114 Problem Set 1 (answer key)

Bi114 Problem Set 1 (answer key) - Bi114 Problem Set...

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Bi114 Problem Set 1 (answer key) 1. Read Blander & Medzhitov 2006 Nature a) What does the localization of I-A b indicate (e.g. Fig. 1a vs 1b)? Please explain. (5 points) Staining of I-A b is used to 1> show the localization of MHCII molecules within the cell; 2> indicate the maturation state of the cell upon different treatments (e.g. Fig.1a- lysosomal localization of MHCII- DCs were not matured by stimulation of apoptotic cells; Fig. 1b- plasma membrane localization of MHCII- DCs were matured by stimulation of microbial cells; etc.) 2.5 points: MHCII localization 2.5 points: DC maturation b) In Fig. 3, what evidence did the authors provide to demonstrate that an antigen needs to be in the same cargo with a TLR ligand (e.g. LPS) to elicit antigen-specific immune response? Based on the data in Fig. 3, please explain why in Fig. 2a, co-stimulation of EAP+ apoptotic cells and OVA+ E. coli leads to the presentation of only OVA but not EAP. (10 points) Figure 3 shows that antigen and TLR ligand must be in the same phagosome to elicit a strong CD4+ T cell reaction against the antigen. Figure 3a and 3b show that IL-2, which is secreted by activated T cells, is secreted by Hel-specific CD4+ T cells at much greater levels when Hel and LPS (a TLR4 ligand) are within the same phagosome than when they are in separate phagosomes or LPS is absent. Figure 3c, d, and e show that MHC presentation of Hel peptides is much greate in dendritic cells that adsorb microspheres containing both Hel and LPS compared to DCs that adsorb microspheres containing only Hel. Thus a more effective adaptive T cell response is mounted against Hel when Hel is in the same phagosome as a TLR ligand. Based on the conclusion above, OVA is presented because OVA+ E.coli also contains TLR ligands, which can be processed in the same phagosome with OVA while EAP+ apoptotic cells don’t contain TLR ligand, which results in no presentation of EAP. 4 points: More IL-2 secreted when Hel and LPS in same microsphere
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Bi114 Problem Set 1 (answer key) - Bi114 Problem Set...

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