To prevent bacteria, viruses, and other microscopic foreign materials that enter the body from destroying it, the human immune system creates a human antibody to identify invaders and trigger a response to destroy them. The antibody is a type of protein commonly found in the bloodstream which corresponds to a specific disease or intruder, known as a pathogen. When a person gets sick, the body produces a human antibody for the disease that caused the illness. If the virus returns, the antibody will latch on to it and the immune system will use that as a signal to destroy all of the virus particles found in the body.
Each human antibody bonds to only one specific particle. Every time the body encounters a new virus or other foreign particle it considers a threat, the body must create a new antibody to match that object. The antibody is a protein structure which is similar to all other antibodies with one exception. The end of the protein varies slightly to match with the particular disease it's meant to block.
The end of the protein is referred to as the hypervariable region. Millions of different varieties can exist, allowing the body to create a human antibody for millions of different foreign particles. This is what makes the body so efficient at fighting off a number of diseases.
Invading particles are known as pathogens, but the actual protein in the particle that triggers the antibody is known as an antigen. On that antigen is a section known as an epitope, which is the area the human antibody recognizes specifically. Once the antibody recognizes and connects with the pathogen, it uses one of three methods to neutralize or destroy the pathogen.
Neutralization, opsonization, and complement activation are the three ways to destroy the pathogen. In neutralization, the antibody simply binds to the pathogen and prevents it from doing anything else, thus stopping the spread of the virus and its attacks. Opsonization involves covering the pathogen in a specific coating which tells the body's phagocytic cells to destroy the pathogen. Finally, complement activation lets the pathogen bind the intruder and then use opsonization to destroy it. Depending on the type of object it encounters, an antibody may be able to destroy the pathogen on its own.
Like any part of the body, the immune system and human antibodies are not perfect. Problems occur when the antibodies attack the wrong particles while ignoring others. For example, certain medical treatments may trigger the body's immune system which then tries to destroy the helpful medication found in the body. In certain diseases, the body may attack its own healthy cells, causing damage and health problems. A disease may also do the opposite and prevent the body from attacking harmful viruses it needs to eliminate.