Types of Immunity
Immunity is the ability of human body to fight against the disease causing organisms. The human immune system has two types of immunity:
- Innate immunity
- Acquired immunity
The innate immune system is the type of immunity that is present naturally in the child at the time of birth. These natural protectors are already present in human body.
The first and the foremost important barrier which prevents entry of the harmful micro-organisms in human body is skin. Skin acts as a barrier to the entry of harmful micro-organism in many vital organs of the body.
Natural secretions of our body also help to prevent microbial growth in our body. Vital systems such as respiratory, gastrointestinal, and urogenital are prevented by the mucus coating of the epithelium lining these systems. Important fluids which are protective in our body are acid in the stomach, saliva in the mouth and tears from the eyes.
White blood cells present in human blood also protect the body from many infections. Macrophages in tissues help in the destruction of harmful microbes entering into the body.
Every one of us suffers from one or other type of viral infection in our life. These viral infected cells produce special proteins called interferon to protect healthy cells from further viral infection.
Acquired immunity, also called the adaptive immune system, involves two processes. The primary response is produced when our body encounters a pathogen for the first time. This is a mild response produced by our body. The secondary response is produced when our body encounters the same pathogen for the second time. This secondary response is highly intensified.
These responses are produced in our body by two types of lymphocytes in our blood. These two special lymphocytes are B-lymphocytes and T-lymphocytes. Whenever a foreign substance enters our body, B-lymphocytes produce proteins to fight them. These proteins are called immunoglobulin or antibodies. T-cells do not produce such proteins, but they help B-lymphocytes to produce them. There are many different kind of antibodies produced in our body. Some of the important antibodies present in human body are IgA, IgM, IgE and IgG.