There are basically three different types of pathogen invasion“strategies” – extracellular, intracellular in non-phagocytes likeepithelial cells, and intracellular in circulating phagocytes likeMacrophages. That is, some bacteria try to remain outside of thehost cells, while other bacteria and viruses get inside differenttypes of host cells and survive there.

A. For EXTRACELLULAR pathogens, describe advantages anddisadvantages of this strategy. How does our immune system detectand eliminate such pathogens? Explain two virulence factors thatthis sort of pathogen can use to survive in its chosenenvironment.

B. For pathogens that are INTRACELLULAR IN MACROPHAGES, explainhow they gain access to macrophages. Describe advantages anddisadvantages of this strategy. How does our immune system detectand eliminate such pathogens? Explain two virulence factors thatthis sort of pathogen can use to survive in its chosenenvironment.

C. For pathogens that are INTRACELLULAR IN EPITHELIAL CELLS,explain how they enter the epithelial cells. Describe advantagesand disadvantages of this strategy. How does our immune systemdetect and eliminate such pathogens? Explain two virulence factorsthat this sort of pathogen can use to survive in its chosenenvironment.