The Normal Microbiota Provides Protection Against Potentially Harmful Organisms and Stimulates

Multiple Choice

The normal microbiota provides protection against potentially harmful organisms and stimulates the immune system. Why would the immune responses to members of the normal microbiota cross-react with pathogens?

A) Because one person's normal microbiota is another person's pathogen-when we pick up "normal" microbes from a different person, they will always cause infection within us.
B) Because pathogens are often more virulent strains of our own normal microbiota, so they will appear similar to those cells to our immune system, and may be acted upon by our immune responses.
C) Because the normal microbiota keeps the adaptive immune responses tuned up, active, and ready to respond to broad, general categories of microbes such as Gram-positive and Gram-negative bacteria and viruses.
D) Because if the immune system isn't used on a regular basis, it loses the ability to respond to pathogens. The normal microbiota keeps the system going so that it can be ready to respond to pathogens when we're exposed to them.
E) Because normal microbiota are often more virulent strains of our pathogens, so they will appear similar to those cells to our immune system, and may be acted upon by our immune responses.