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August 6, 2021

Science Cast

Bridging the gap between Scientists and the Public

What is immunity?

4 min read
People who have better acquired immunity are those with history of infections. They are likely to be more immune to the specific disease as compared to someone who hasn’t had the disease before. This is because the action will be more specific and lethal to the pathogen. Better still one can be vaccinated against certain disease especially when they travel to places where its common.

Think about the time you felt sick. I don’t think it was pleasant. Disease is when the body is not working normally. It is caused by a pathogen such as microorganisms or any other foreign substance.

Immunity is how the human body protects itself from foreign things like microorganisms such as bacteria, viruses, and fungi and their products like toxins, pollen from plants, animal hair, chemicals, foods, drugs, dander etc.

There are two types of immunity; Innate and Acquired Immunity. Natural or Innate immunity is present from birth and readily available but not specific to a certain foreign material. Acquired immunity, as it names suggests, only happens once someone has been in contact with the foreign particle. The body is able to remember the kind of infection thus ready to fight the pathogen before it causes a disease.

Natural/Innate Immunity

A pathogen is commonly known germs. It causes diseases. Pathogens include microorganisms such as bacteria, viruses, fungi etc. Ways in which nature immunity is done include skin, mucous membranes, fever, immune cells, inflammation and other biologically active substances.

Ways in which Natural Immunity occurs.

  1. Unbroken skin is able to protect the body from most organisms and foreign substances. However some may enter through the hair pores into the sebaceous glands that an oily substance called sebum. The acidic pH, fatty acids and enzymes of sweat and sebum help in destroying foreign substances.
  2. Mucous membranes include respiratory tract (nose & trachea), gastrointestinal tract (mouth, gullet, stomach & intestines) and the vagina. They have epithelial cells which produce mucus and hair-like projections called cilia. Mucus traps the pathogens and substances such as pollen. Cilia beat the mucus carrying the pathogens towards the openings. The acidic pH and enzymes in the saliva, stomach, bile and vaginal secretions help in destroying the pathogens. Hairs in nostrils and cough reflex helps in trapping and removing the foreign substances. Alcohol, cigarette smoke and narcotics can reduce the action of these defense systems.
  3. Fever is an increase of body temperature to help in fighting pathogens. It is caused by toxins released by microorganisms such as bacteria. These toxins enter immune cells called monocytes that produce pyrogens such as Interleukin-1 and Interferons responsible for increasing the body temperature. This however may interfere with normal working of the body which is not good.
  4. Pain is caused by inflammation due to an injury or infection. Inflammation is seen as swelling, redness, heat, pain and loss of function. The body detects the injury and sends all agents against the pathogen causing inflammation.
  5. Extracellular killing is done by natural Killer (NK) cells and cytotoxic T Lymphocytes (Tc). They recognize unique structures on the surfaces of abnormal cell structures as cancer cells or cells infected by viruses. The NK and Tc cells release molecules that can make holes on the cells making them to die when its contents are released to the environment.  The molecules can also enter the abnormal cells causing a programmed cell death due to breaking down of DNA called apoptosis.
  6. Phagocytosis is when pathogens and foreign are eaten by cells called phagocytes and destroyed with the assistance of granules. The granules contain enzymes that destroy the pathogens. These phagocytes include monocytes, Neutrophils, Mast cells, Basophils, eosinophils and macrophages( splenic, microglial in nervous system, kupffer in liver, alveolar in lungs and peritoneal)
  7. Biologically active substances such as degradative enzymes, toxic free radicals , acids, inhibitors of growth, acute phase proteins and  interferons  act against pathogens in different ways.
  8. Cellular response. Once the pathogens penetrate the skin and mucous membranes, there are other ways apart from the ones mentioned above that they can be destroyed. This is with the use of cells that will be explained later.

This can be made better by eating natural foods that provide the cells including skin cells with the essentials they need to work properly which involves defending the body.

Acquired Immunity

In contrary to innate immunity, one is not born with acquired immunity unless one gets in contact with the antigen in the case of a disease of a vaccine (weaker form of antigen). This is only seen in vertebrates.

An antigen is any foreign substance or pathogen that can be recognized by the immune system. This antigen can interact with an antibody produced by immune cells called B cells and be destroyed. The body produces antibodies specific to the antigen. Some act on it while other antibodies remain as memory antibodies. In the case of the same antigen entering the body, the specific antibodies are ready to kill the antigen before it causes a disease.

This initial contact with the antigen is called Immunization. There are three types of immunizations. This includes;

  1. Active immunization that involves giving of an antigen, normally a weaker, to an individual as seen in most vaccinations. Vaccination is the process of causing acquired immunity.
  2. Passive immunization is when an antibody specific to an antigen is given to an individual who has been actively immunized to a non-immunized.
  3. Adoptive transfer is when immune cells producing antibodies are transferred from one person to another.

When the body responds to an antigen, it can take action using a cellular or a humoral response as seen in T and b cells respectively. Cellular involves use of cells to fight a pathogen as explained in some of the natural ways of immunity. Humoral involves the use of antibodies produced by immune cells which are able to capture and antigen for destruction.

People who have better-acquired immunity are those with a story of infections. They are likely to be more immune to the specific disease as compared to someone who hasn’t had the disease before. This is because the action will be more specific and lethal to the pathogen. Better still one can be vaccinated against certain disease especially when they travel to places where it’s common.

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