Today we are going to talk about a story of immune system fighting against virus.

免疫系统里得兵士：白细胞
White Blood Cells in Immune System

White blood cells are a group of specialized soldiers in Immune system. Although they are not a lot, they work together to identify and destroy pathogens.

The story starts from a sneeze. When you sneeze, the air particles will be sprayed in a speed of 160km/h, and they can reach further than 3.6m. The liquid with pathogens will be transmitted to other persons. Let’s take a look at a droplet of snot under microscope. Green color means particles in the air. Bigger cells are white cells that protect us from pathogens. There are about 400 thousand white blood cells in one droplet of blood.

Once infected, the first response from your body is fever. It tries to slow the growth of pathogens by raising body temperature.

第一轮攻击：巨噬细胞
First Round：Macrophage

Once there are more viruses, macrophages will destroy pathogens by engulfing and digesting them. Macrophages will die with pathogens. They help start the body’s immune response to antigens, which is a substance stimulating a response by immune system.

免疫系统里其他三大年夜兵士
Other soldiers in the Immune System

The death of macrophages activate helper T cells.  Helper T cells recognize the viral antigen on the macrophage。Helper T cells trigger two responses: the T cell response and the B cell response.

第二轮：杀手T细胞
Second Round: Killer T cell response

Killer T cells recognize the viral antigen on infected body cells. The killer T cells destroy the infected cells and cause the cells to release the virus particles. Lack of specialized weapons, this fighting is not very effective.

关键决胜点：B细胞
Key Point to Win: B Cells

Once activated by helper T cells, B cells recognize the shape of the viral antigen, then make and release antibodies. Antibodies bind to viral antigens forming clumps, and tag the virus for destruction. And antibody’s shape is specialized to match an antigen like a key fits a lock. It’s easy for killer T cells for next stage of fighting.

反攻时刻
Time to win

With the help of antibody, killer T cells destroy infected cells and virus particles. Most viruses will be killed and be got rid of the body.

We won the war against virus and came back to our happy daily life.

故事得最终
The End of the Story

Your body will go back to normal after the war. Billions of T cells and B cells will die, but they will leave memory cells. Memory cells are T cells and B cells that “remember” a special pathogen. Once the pathogen enters, your body immediately starts to attack pathogen.

Tomorrow we are going to talk about how to get immunity and the history and function of vaccination.

B站上有本阶段课程得完整视频，迎接存眷：

https://www.bilibili.com/video/av91168110