Immunity

Immunity is the ability of the body to resist certain diseases and poisons. Immunity can also be defined as the ability of the body to defend itself against infectious agents, foreign cells and even abnormal cells such as cancer cells



The scientific study of immune system is called immunology.

Immune system

The immune system comprises of a group of cells, molecules and tissues that help defend against disease and other harmful invaders.

The invaders include disease-causing organisms (pathogens) such as bacteria, fungi, protozoa, virus and worms. A key feature of immune system is its ability to destroy foreign organisms, leaving the body‟s own health tissues alone.

The immune system consists of white blood cells, lymph nodes, spleen, liver and bone marrow.


Types of immunity

Basically there are two types of immunity
1.Natural immunity
2.Artificial immunity


Natural immunity

Natural immunity is that which an individual is born with.

Natural immunity can be divided into categories, namely:
a.Natural active immunity
b.Natural passive immunity


  • Natural active immunity:
This immunity develops in a body after a natural infection. After infection, antibodies are produced in the body. The antibodies normally reside in the blood or in other parts of the body. The body can make more antibodies whenever the pathogen tries to attack the body again
.

  • Natural passive immunity:
This type of immunity is achieved during development of the foetus where antibodies pass from the mother to the foetus through placenta or through the mother‟s milk after the baby is born. The antibodies disappear from the infant a few months after birth.


Artificial immunity

Artificial immunity is that which an individual acquires during his/her life time.

There are two types of artificial immunity
a. Artificial active immunity
b. Artificial passive immunity


  • Artificial active immunity 
This is immunity introduced in the body by immunization.
Immunization is the process of introducing a vaccine into the body of an animal in order to increase its ability to produce antibodies. These antibodies protect the person if he/she is exposed to the actual disease.

  • Most vaccines contain disease-causing bacteria or viruses that have been killed. 
  • Others consist of the live germs but in a weakened form or attenuated. 
  • Toxoid vaccines are made from poisons produced by disease-causing organisms. 
  • These poisons are chemically treated so that they provide immunity without causing disease. 
  • Some vaccines are made from parts of disease-causing organisms. 

Vaccines have been developed against many diseases such as chicken pox, diphtheria, influenza, measles, meningitis, mumps, pneumonia, poliomyelitis, cholera, rabies, rubella (German measles), tetanus, whooping cough and yellow fever.Vaccines can be taken through, injection, rubbing or the mouth (orally).


  • Artificial passive immunity 
This type of immunity involves the injection of serum into the body of an organism. Serum contains antibodies that have been formed in another person or animal. It provides immediate protection from infection and lasts for weeks or months and after that period there are no antibodies left in the body and therefore no immunity.
  

Factors which Affects Body Immunity

Factors which may lead to low of body immunity
  1. Alcohol and other toxic drugs. 
  2. Lack of immunisation. 
  3. Lack of proper balanced diet. 
  4. Inability of the body to produce antibodies and white blood cells. 
  5. Pathogens of HIV (Human Immunodeficiency Virus)