How the immune system works: a conversation with a specialist

Welsh: Now scientists are divided into two types: those who always thought a pandemic was just around the corner, and those who never imagined the problem could grow to such proportions. Which type are you?

Butterfield: I'm not surprised that this has happened, given the signals we've been seeing from all over the planet. People were increasingly encroaching on previously untouched natural realms, exposing themselves to unknown dangers. I watch a lot of zombie apocalypse movies, so I think we still got off easy.

Hamblin: Some movies have speculated about what a pandemic might look like, like Infect and Epidemic. Question on the immunology side: COVID-19 affects people very differently, is that because our immune system reacts differently to it?

B: Absolutely. You, for example, may have five times as many white blood cells as I do. Everyone is very different in that way.

U: Could you explain to me as simply as possible how the immune system works?

B: Sure. The immune system is wonderful in its complexity and specificity, which makes it difficult to discuss some of the details of how it works. Plus, we often use immunological jargon.

The immune system protects us from infections and any other threats from the environment. There are cells and molecules in the blood that react immediately when danger is detected. Then another part of the immune system starts its work. It takes about a week for it to get up to speed as much as possible. That's why it often happens that we get sick, and after a while the body deals with the disease on its own.

X: My favorite metaphor on the subject is that when a village is threatened, the villagers grab their pitchforks and torches and immediately set out to defend themselves. And about a week later, a squad of SEALs arrives and they act with much greater efficiency.

Q: Antibodies occur after about a week, right?

B: The SEAL response occurs after a week, when the immune system finally figures out what the threat is. Initially, T cells and B cells are important. B-cells produce proteins, which is what we call antibodies. They swim around in the blood looking for specific threats that they specialize in neutralizing. When a threat is found, the antibodies stick to the outside of, for example, a virus and block the part of it responsible for interacting with the occupied organism. The antibodies neutralize the virus, after which it loses its ability to enter other cells in the body.

H: Sounds like the very same immunological jargon. It's very important to understand that antibodies have a clear specialization and can block only certain viruses. And sometimes antibodies cannot defeat a virus at all, as with HIV. Imagine that the virus has bulletproof armor and even Navy SEALs cannot neutralize it.

B: Yeah, shoot all the bullets you want, sometimes it's just useless.

W: I recently took an antibody test and got a negative result. Does that mean there are no antibodies in my body?

B: If the test is of good quality and the procedure was performed without any irregularities, you really don't have antibodies. The test could ask a general question: Did the body see the virus, and if so, did it respond by creating antibodies? Or the question could be quite specific: if the body saw the virus, did it create effective antibodies that were able to fight it off? Most tests, as far as I know, ask a general question.

H: How likely do you think it is that the antibodies found would be able to neutralize the virus?

B: If you have antibodies at all, a certain amount of them will be effective. But we can't yet determine their exact amount, whether it's enough and how long they will be active.

Q: Approximately how many antibodies should a strong immune system have?

B: Hospitals, universities and private companies are constantly looking into this question. We hope that the flu shot can protect the average person for a year. Over the course of that year, data is collected and then a rough figure is derived.

Q: I once read that antibodies disappear over time. What does that mean?

B: It's a normal process of self-regulation of the immune system. Going back to the example with the defense of the village: when the SEALs handle the enemy, the point of their stay will be gone, they'll leave, leaving the villagers with pitchforks and torches to live a normal life. But, of course, it makes sense to leave a couple of elite soldiers behind just in case.

W: What is the main mystery of the coronavirus? You probably think about it a lot.

B: My biggest worry is the long-term effects of the pandemic, which we're only beginning to notice now. We had hoped that the coronavirus would be something like the common cold, but in a slightly more severe form -- those hopes have not been realized. It is already clear that the virus has deleterious effects on various organ systems and provokes residual effects after recovery.

H: Developing the metaphor, stationing the military in a small village is certainly a necessary measure, but it can also have negative consequences.

B: Yes. The Navy SEALs might find it necessary to blow up some buildings, they would then have to be rebuilt, and that would take a lot of time and resources. And ten years later you'll realize that the bombs were toxic and poisoned all the soil in the village.

H: And you find out that the villagers have turned into zombies.

W: That's terrible! I'd like to clarify this: the antibody test doesn't confirm the presence of T-cells, which also have a protective function?

B: Yes, it does. First, we have to learn how to find a specific virus-oriented T cell. So far, we can't always achieve this, but we are actively developing in this direction.

H: That's good news. A lot of people started to get worried when they found out that antibodies disappear over time. But now you are confirming that there are other cells that can protect the body when the antibodies weaken.

B: The vaccines being developed are designed to create both antibodies and T cells. Thus, there will be a dual immune response. We don't know yet how effective this will be, but the fact that two mechanisms will be involved at once is certainly good news.

Probably there will be no toxic munitions or blown up buildings at all. We may have to sacrifice a little to defeat the enemy, but the SEALs will certainly be able to go home early.


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