Immunity

Immunity is what protects you from getting a certain virus or disease. One type of immunity is what you already have in your body called, first line defenses. The first line defenses are your skin and respiratory, digestive, and circulatory systems.

Your body also has internal first-line defenses. Your respiratory system traps pathogens (bad guys) in cilia, which is a hair-like structure, and mucus. The mucus weakens the cell walls of the pathogens. The pathogens are pushed out when you sneeze or cough.

Your digestive system has A LOT to do with getting rid of pathogens, such as mucus, saliva, enzymes, and hydrochloric acid solution. The saliva kills bacteria in your mouth. The enzymes in your stomach, pancreas, and liver help destroy pathogens. The hydrochloric acid, which digests your food, helps kill some bacteria and stops activity of some viruses that enter your body on the food you eat. The mucus on the walls of your digestive tract contain a chemical that coats bacteria and prevents them from binding into the lining of your digestive organs.

When the pathogens get past your first-line defenses, they cause inflammation. When tissue is damaged or infected by pathogens, it becomes inflamed. When something is inflamed, it turns red, feels warm, swells, and hurts.

Specific Immunity
When your body fights disease, it is battling complex molecules called antigens that don’t belong. Antigens can be separate molecules, or they can be found on the surface of a pathogen. When your immune system recognizes foreign molecules, special lymphocytes called T cells respond. A type of T cell, called the killer T cell, releases enzymes that help destroy invading foreign objects. Another type of T cell, called the helper T cell turns on the immune system. The helper T cells stimulate other lymphocytes, known as B cells, to form antibodies. Antibodies are a protein produced by the body's immune system that recognizes and helps fight infections and other foreign substances in the body. The antibody’s job is to attach on to the antigen and make is useless.

B cells are lymphocytes that have specific antibodies for certain pathogens. Memory B cells stay in the blood after clearing out a pathogen. The B cells remember what happened, so they can defend against an invasion by the same pathogen at a different time.

Active Immunity
Antibodies help your body build defenses in two ways that are either active or passive. In active immunity, your body makes its own antibodies in response to an antigen. Passive immunity results when antibodies that have been produced in other animals are introduced into your body. When a pathogen invades your body, the pathogen multiplies, and you get sick. Your body immediately starts to make antibodies to attack the pathogen. You normally get better once enough antibodies are formed.

Also, another way to develop active immunity to a disease is to be inoculated with a vaccine. The process of injecting a vaccine or giving a vaccine by mouth is called a vaccination. A vaccine is a form of the antigen that gives you active immunity to a disease. Vaccines can only prevent a disease; therefore, they are not a cure. Passive immunity does not last as long as active immunity.


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Immunity

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