Question

Part A. A neutrophil is chasing a pathogenic bacterium. Explain how it will detect and move toward its prey and how it will change course when necessary.

Part B. A mutation that destroys the GTPase function of Ras is an initiating event in many cancers. Describe how constant activation of Ras will cause increased expression of Cyclin D and S phase genes by the transcription factor E2F.

Part C. When the transcription factor E2F is activated, it can amplify its own gene expression and leads to the transcription of Cyclin E. Cyclin E with Cdk2 can phosphorylate Rb, removing the Rb’s inhibitory effect on E2F. These are two positive feedback loops that occur in E2F activation. What do you think is the effect and purpose of these two feedback loops?  

Answer 1

Answer: Part A:

Neutrophils plays a major role in innate immune system. Neutrophils gets produced and matured in the bone marrow. When bacteria infects the body then neutrophils gets recruited from the bloodstream to the site of bacterial infection. Bacteria produces exogenous products which are detected by neutrophils through TLRs ( Toll like receptors), GPCRs ( G protein coupled receptors) and cognate immune receptors. When neutrophil senses the receptor signal it responds to the stimulus by leaking out from the blood vessels and moves towards the site of infection. Neutrophils goes to the site of infection and then phagocyte the bacteria. This phagocytosis of bacteria happens in several steps which involves rolling and adhesion of neutrophils on the endothelial cells then adhesion of neutrophils after this extravasation of neutrophils happens through the endothelium then neutrophils migrates towards bacteria and finally kills the invading bacterial pathogens by phagocytosis. Neutrophils creates lethal environment to kill the bacteria by using NADPH oxidase derived ROS (reactive oxygen species), antimicrobial peptides, neutrophil extracellular traps (NET) and granular cytotoxic components.