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How do innate immunity and acquired immunity work in the human body

Is Immunity Innate?
Innate Immunity and Acquired Immunity
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Modern people can maintain their health despite exposure to fine dust, various toxic substances, and unexpected infectious diseases such as COVID-19 because the human body's immune system operates 24/7. Weakened immunity increases the risk of being exposed to various diseases. The difference between people who are susceptible to colds or influenza and those who are not lies in the ability of their immune system to protect them.

Our immunity is constantly fighting an invisible war against various viruses and evolving bacteria. The immune system is divided into innate immunity, which reduces the likelihood of catching infectious diseases, and acquired immunity, which combats unfamiliar invaders. These two immune systems complement each other and engage in continuous battles to protect our health day and night.

What Is Immunity, a Strong Guardian of Our Body?
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Immunity refers to the mechanisms that defend against harmful antigens invading the internal environment of the human body. Simply put, it is the body's ability to resist specific pathogens or toxins. Immunity is broadly divided into two types: innate immunity, which is the natural immunity present from birth, and acquired immunity, which is developed through infection or vaccination.

Innate Immunity From Birth

Innate immunity refers to the immune organs, cells, and substances inherited from the mother at birth. Immune organs include the bone marrow, spleen, thymus, lymph nodes, and tonsils, which produce immune cells and substances. Immune cells consist of lymphocytes (white blood cells), macrophages, and natural killer (NK) cells that fight against invading bacteria or viruses. Immune substances, such as interferon and cytokines, are proteins produced or secreted by these immune organs or cells. Innate immunity provides an immediate response to eliminate invaders when microorganisms like viruses or bacteria invade, even if the body has never encountered them before.

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Excellent Attacker 'NK Cells': Representative Innate Immune Cells

NK cells are adept at identifying cells infected with viruses or cancer cells and directly attacking and eliminating them. As defense cells at the forefront of the immune system, they play a crucial role in protecting our body from invaders. The importance of NK cells has been underscored by their ability to prevent the occurrence, proliferation, and metastasis of cancer cells. Additionally, NK cells effectively control cancer stem cells, which are pivotal in cancer recurrence. By detecting and immediately removing cancer cells and virus-infected abnormal cells, activated NK cells are vital in maintaining a balanced immune system.

Acquired Immunity: Responsible for Fighting Against Unfamiliar Invaders

Acquired immunity develops after birth and is crucial for fighting unfamiliar pathogens. When a virus invades, the body produces substances to combat it. These viruses are called antigens, while the substances fighting against them are known as antibodies. If the human body lacks antibodies when a pathogen invades, it raises the body temperature to hinder bacterial proliferation and gathers the necessary substances for immunity to combat the infection. If the body successfully protects against the infection, it remembers the virus and creates acquired immunity. This principle explains why, after catching a cold, our body makes antibodies to exterminate the cold virus and ultimately cure it. Additionally, vaccination is an example of utilizing acquired immunity: a weakened virus is injected into the body, prompting it to produce antibodies. Acquired immunity is also referred to as 'artificial immunity' because antibodies are artificially produced.

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Immunoglobulin; an Antibody Fighting against Antigens

An antibody recognizes an antigen and forms an antigen-antibody complex to neutralize the antigen. Immunoglobulin (Ig) is an acquired immune antibody substance, a glycoprotein molecule produced in response to antigen stimulation, triggering an immune response. It specifically binds to antigens in the blood, helping to neutralize them and remove pathogenic microorganisms such as bacteria and viruses through sedimentation or aggregation reactions. Additionally, Ig induces various immune functions by interacting with other components of the immune system.

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How Does Our Body React When an Antigen Invades?

When an antigen invades, the human body initially responds by increasing its temperature to kill viruses that are sensitive to temperature changes. If the virus is not destroyed, the immune response manifests as inflammation. The inflammatory response occurs in three stages: First Stage: Macrophages engulf the virus, while NK (natural killer) cells eliminate virus-infected cells by producing interferon to inhibit virus growth and inducing apoptosis. Second Stage: White blood cells block the movement of infected cells or generate antibodies, leading to a battle between the virus and antibodies. Third Stage: The remnants of the battle are removed, and tissues are regenerated. However, the inflammation generated during this immune response can decrease overall physical function due to oxidation and a lack of oxygen, ultimately adversely affecting our health.

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