PartⅢ Script of the Audiovisual Material
Microbes and Immunity
We have microbes all over us.There are a number of host cells by about ten to one.It is clear that the microbes that we live with that are in our body and on our body are very important to our health.
We are interested in how microbes influence the immune system,particularly immune system of the gut.There are proximally 100 trillion microbes in the oral cavity and in the small and large intestine.(https://www.daowen.com)
In this project,the question really was,“Are they uniquely qualified to live on us？”or“Could they be substituted by microbes that come from another species？”We couldn't take microbes out of humans and put another set of microbes in.Instead,we did it in the mouse,where we started with germ-free mice.These mice truly have no microbes on them.We actually check them every week to make sure that just in our handling of them they don't acquire bacteria.So now in each isolator,we had mice colonized with either human or mice microbes.We really want to see if there is functional deficiency in the case of mice with human microbe species.So we did,we challenged the mice with Salmonella Typhimuriumthe.It's a pathogen that causes the intestine to get inflamed.What we found was that their immune systems were not functioning in full force,but these mice could withstand infection when colonized with mice microbes.
To examine this further,we colonized the mice with rat microbe species,and actually the rat microbes were no more useful to the mouse than human microbes.These studies provide evidence that microbes and,in our case,humans have coevolved over years to have a beneficial relationship to each other.This also fits in with the hygiene hypothesis.Our clean environment may affect the microbes that inhabit us that provide resistance to infection and perhaps to other diseases as well.