Types of Immunity

Did you have measles or chicken pox when you were young? If you did, most likely you will never get them again as you have acquired immunity against these diseases. Do you know what immunity means?
Immunity refers to the ability of an organism to defend itself against infection by pathogens. Immunity refers to the ability of an organism to defend itself against the infection by pathogens. Immunity depends on the presence of lymphocytes and the production of antibodies which give a specific immune response. The various types of immunity are active immunity (natural and artificial) and passive (natural and artificial).
 

Inherited natural immunity is the immunity which is inherited by an individual through the placenta or mother’s milk. Active natural acquired immunity is acquired after a person recovers from an infection, for example, measles or chickenpox. The body then has the ability to produce more antibodies rapidly against further attack by the same type of invading antigen. Antigens are foreign proteins or polysaccharides usually found in the surface of cells, for example, bacteria and viruses. When they enter the body, they stimulate the lymphocytes to produce antibodies. Antibodies destroy the antigens or neutralise the toxins produced by pathogens.
 

A vaccine contains killed or weakened antigens. When the vaccine is injected into the bloodstream, the lymphocytes in the body produce antibodies against that particular antigen. Vaccination produces active artificial acquired immunity: active because the antibodies are produced by the body itself, artificial because it is obtained through vaccination. This process is known as immunisation. When antibodies are transported from the mother across the placenta to the foetus or through the mother’s milk to the young infant, this gives passive natural immunity for a few months.
 

Passive artificial immunity is obtained by injecting serum containing specific antibodies prepared from the blood of humans or other animals. This is normally used to treat patients who are already seriously ill, for example from rabies, botulism, tetanus or snake bites. The antibodies obtained from other individuals give quick temporary immunity. This type of immunity cannot last for several weeks or months because the foreign antibodies break down in the body and are not replaced.