It has been about 10 months since the first confirmed case of the novel coronavirus occurred in Japan. Because of this, many parents are paying extra attention to protect their families.
Our topic today is “immunity.” What is immunity, and how does it work against infection? We sat down with Keio University’s Professor Emeritus and obstetrician Dr. Yasunori Yoshimura to learn more.
Our Body’s Multi-Stage Self-Defense System
-- People often say that in order to avoid infectious diseases, you need to keep up your immunity. But what even is immunity?
Dr. Yoshimura: Our bodies have a self-defense function that attacks foreign bacteria and viruses to maintain normal status. This function is known as the immune system, and immunity is the power to resist pathogens. Immunity is largely divided into two types. One is mucosal immunity, a defense system that prevents viruses and bacteria from entering the body, and the other is systemic immunity, an elimination/attack system that fights foreign matter that has made their way in.
-- So there’s two, both the mucosal and systemic immunities.
Dr. Yoshimura: Right. If I explain further, our skin is the first barrier that keeps foreign matter out. We have been highly encouraged during these Covid times to wash our hands and warned against touching our faces; this is an attempt to prevent the virus from transferring from our skin to our mouths.
-- It’s become completely routine for me to wash my hands immediately when I get home now. I saw on the news that that might be why the national number of flu patients in the winter of 2019~20 were the lowest of the past 12 years.
Dr. Yoshimura: Indeed. Handwashing is important. That being said, even if pathogens transfer from the skin to the mucosas, I want you to know that there are immune substances/IgA antibodies (immunoglobulin) in the eyes, nose, mouth, intestines and all over the body that will fight to neutralize those invading particles.
-- So that’s mucosal immunity coming into play. But not everything can be guarded by that, right?
Dr. Yoshimura: That’s right. After that, it’s systemic immunity’s turn. Systemic immunity works through the lymph nodes, spleen, and blood. The innate immune system reacts first immediately when the body senses pathogens, followed by the acquired immune system.
-- I see, so systemic immunity has two stages.
Dr. Yoshimura: The innate immune system refers to the white blood cells neutrophils and macrophages, which eat pathogens. Meanwhile, the acquired immune system stems from the viruses and bacteria the white blood cells have disassembled, whose information can be used to create antibodies for targeted attacks. Our bodies have the ability to create the perfect antibody to counter any pathogen, remember the characteristics of past immune responses, and react accordingly for similar invasions in the future. In other words, the acquired immune system is acquired during a lifetime of encountering various types of pathogens. Antibodies also activate neutrophils and macrophages, so the innate and acquired immune systems work together to protect the body.
-- The immune system is so complex. This may be a silly question, but what is the difference between immunity and antibody?
Dr. Yoshimura: To put it simply, antibodies are the last resort against foreign matter. The vaccines used to make antibodies rely on the way the acquired immune system works. By introducing the body to pathogens with weak toxicity before it is infected, the body creates antibodies in advance and therefore prevents severe infections.
A healthy lifestyle and balanced diet will regulate the immune system.
-- Do different individuals have different immune levels?
Dr. Yoshimura: There are definitely individual differences, and it doesn’t stay the same during a lifetime. For example there are major bodily changes during pregnancy, so pregnant women often experience an imbalance in their immunity and cardiopulmonary functions. In addition, small children have not yet been exposed to various foreign matter and bacteria, and therefore do not have the same level of immunity as adults. Aging is another cause of decreased immunity. Generally, pregnant women, children and the elderly have low immune levels.
-- I often see advertisements for food products that claim to “increase immunity,” but can our diet really increase our immunity?
Dr. Yoshimura: I don’t believe ingesting certain foods will guarantee increased immunity. There’s no medical evidence for this. But, a healthy diet should be part of maintaining a regular lifestyle. Lack of sleep, an irregular lifestyle, unbalanced diets, and excessive stress are all said to contribute to poor immunity. Decreased immunity makes the body more vulnerable to pathogens. When you stay up late doing work, don’t eat proper meals, heavily drink, barely sleep… this sort of lifestyle will surely harm your immune system.
-- In converse, does a healthy lifestyle with ample sleep and a balanced diet preserve our immune system?
Dr. Yoshimura: Yes, more specifically it preserves our mucosal immunity. As I said before, the mucosal immune system’s IgA antibodies are vital to stopping bacteria and viruses from entering our bodies. IgA antibodies are present all over our mucosal parts, and will inactivate not only bacteria and viruses, but various kinds of pathogens.
-- These mucosal parts refer to our eyes, nose, mouth and intestinal tract right?
Dr. Yoshimura: Exactly. The surface area of the gastrointestinal tract, specifically the small intestines, is as wide as one tennis court when laid flat and is an active part of preventing infections. When invaders are detected in this area, a large amount of IgA antibodies are secreted to stop, break down and expel the pathogens into waste. As a side note, breast milk is full of IgA antibodies, especially in the few days after birth. Protecting the mouth and intestines is one of the most important reasons why our babies drink colostrum (first milk) immediately after birth.
Though Japan has experienced lockdown, more and more people are going out now that the state of emergency has been lifted. But the end of the fight against the novel coronavirus is not in sight, and it seems that the number of newly infected people will continue to be uncertain. We hope that you will keep Dr. Yoshimura’s immunity advice in mind, and that his message will keep everyone in your family safe and healthy.
Dr. Yasunori Yoshimura
Born in 1949. Keio University Professor Emeritus, Obstetrician and Gynecologist. Chairman of the Japan Society of Obstetrics and Gynecology, chairman and infertility specialist of Japanese Society of Reproductive Medicine. He has treated over 2,000 infertility patients, delivered over 3,000 births, and treated numerous others. He served as a special advisor to the Cabinet during the 2nd to 4th Abe Cabinets to address the declining birthrate and parenting. Presides over the “Yasunori Yoshimura Environmental Research Institute of Life.”