I'm an immunologist. And for the past 15 years or so, my research group has been studying how the immune（免疫的） system responds to infections（感染） and vaccines（疫苗）. I'd say up until about four years or so ago, even when I tried to explain the research to my own family, the response was a bit like, oh, that's nice, dear, right? But with the onset（开始） of the COVID-19 pandemic（全国流行的）, everything changed. And all of a sudden, the details of what we study-- immune responses to the virus, what the virus was doing, whether or not the vaccines would be successful-- all these kinds of things become a great interest to the global public. And while I was perfectly comfortable talking about some of these issues with my colleagues who are trained immunologists, I and many others were then suddenly tasked with communicating these complicated（复杂的） concepts（概念） to the general public, who are now, all of a sudden, very interested.

  And I think it's fair to say that none of us really had any practice or, frankly（坦率地）, skill in this arena（竞技场）. And so the advice that I was often given（做） was to simplify, craft（精巧地制作） my message that it could be understood by sixth graders. And that's exactly what I did at the beginning. And I tried to simplify things so they could be understood by elementary（基本的） schools. And I thought I was really killing it in this process. And so then when I went around looking for the throngs（一大群） of cheering（使振作） sixth graders who were hanging on my every word, what I instead found were groups of people who were deeply（深刻地） interested in the details.

  The bottom line is, if you're actually trying to look up to see what I have to say, then the reality is that you're probably interested in the deeper science. And by simplifying just for the sake（缘故） of simplifying, I was sort of doing a disservice because I was glossing（使光彩） over some of the complexity（复杂） that I think, anyway, makes the immune system just beautiful to study. And by glossing over that complexity, I think what I was also doing is losing an opportunity to communicate not only what's happening in the context of the COVID-19 pandemic, but the future of immunological therapies（治疗）. So today, I'd like to correct for my past transgressions. And not dumb（哑的） it down for you at all. Instead, what I'm going to do is to try and make complex topics understandable（可以理解的） and explain how the immune（免疫的） system works（使工作）.

  So I'd like to first start off by talking about a term called the adaptive（ 适应的） immune（免疫的） system. I'm sure you've all heard of the immune system. Maybe some of you have heard of the adaptive immune system. So what is that? To understand that, I think we need to go back through some historical context. We've known for millennia that the immune system is actually really good at dealing with all sorts of things that come its way.

  Get infected（传染） with the virus, you clear it. Get infected with a different virus, you clear that. A bacteria（细菌）, a fungus（真菌）, a parasite（寄生虫）. The question has always been, how does the immune system deal with such an array（数组） of diverse（不同的） threats（威胁）? Back before we really knew, one of the theories had been that the immune system and the cells（细胞） that it produces are a little bit like silly putty. They're just sort of lying in wait.

  And so when it encounters（遭遇） a new virus, it sort of molds（模子） or adapts itself to that particular virus. So that's the origin（起源） of the term, the adaptive immune system. But what we've learned from decades of basic research is that that's not exactly how it works. And instead, what happens is that the immune system starts developing enormous numbers of cells, each one just a little bit different than the other. You can think about it like a series of keys. And instead, what it does is it basically（基本上） generates（产生） an enormous numbers of keys, each one with a slightly different shape than the other.

  And those keys are basically floating（漂浮） around your body, looking for any signs of things that are different than yourself. If it happens to encounter something like a virus, and maybe only 1 in 100,000 of those keys would actually fit, then those keys then start to lock into that virus and turn it so that the virus can't replicate（复制） anymore.