Question 1: Based on the figure presented above, what is the most likely ligand for TLR-XX? Be as specific as possible, and justify your answer based on these data.

Question 2: Based on these data, where would you MOST likely find toll-like receptor-XX (TLR-XX) among the following options? Justify WHY you selected the option that you chose for full credit. Your justification must be based on the data that are presented here, not the type of bacteria. 

A. On the cell surface

B. In the endosome/ lysosome

C. In the nucleus

D. In the mitochondria

E. In the endoplasmic reticulum  

Question 3: Would you predict that TLR-XX is able to recognize other types of Gram-negative bacteria, in addition to the one that was used in this experiment?  Explain WHY or WHY NOT?

NK cells and Red Blood Cell tolerance: Red blood cells (RBCs) lack a nucleus and do not express MHC class I proteins. Although RBCs express CD47, a cell-surface protein that is associated with protection from cell-killing, its expression alone does not explain why NK cells do not kill RBCs1.

1.   Pulak Ranjan Nath, Dipasmita Pal-Nath, Ajeet Mandal, Margaret C. Cam, Anthony L. Schwartz, David D. Roberts; Natural Killer Cell Recruitment and Activation Are Regulated by CD47 Expression in the Tumor Microenvironment. Cancer Immunol Res 1 September 2019; 7 (9): 1547–1561. https://doi.org/10.1158/2326-6066.CIR-18-0367

 (Note this reference if provided for your information – You do not need to read this paper to answer the question 4)

Question 4: Based on your understanding of how NK cells distinguish between target cells for cell-killing and healthy cells that are not killed, explain why RBCs are not killed by NK cells. Using complete sentences support your answer with evidence from the suggested videos and/or readings.