Immunity is defined as the body’s ability to destroy pathogens or other foreign materials and to prevent further cases of certain infectious diseases. The different types of immunity or defence mechanism: Innate immunity and Adaptive or Acquired Immunity.
Innate immunity is inherited by the organisms from the parents and protects it from birth throughout life. It is also known as innate or natural or familial or genetic immunity. It is of two types external (first line of defence) and internal (second line of defence). Acquired immunity is also known as specific defence mechanism or third line of defence. It is of two types: natural or active and artificial or passive. Active immunity is produced by clonal selection and expansion. Passive immunity occurs when antibodies produced artificially are injected into a person to counteract antigens such as snake venom, rabies, tetanus toxin and Salmonella infection.
Active Immunity vs Passive Immunity
1. It is produced due to contact with pathogen or its antigen.
2. Immunity is not immediate. A time lapse occurs for its development.
3. It lasts for sufficiently long period, may be life long.
4. Antibodies are produced by the body in response to pathogen or antigen.
5. Side effects are very few.
1. It is produced due to antibodies obtained from outside
2. Immunity develops immediately.
3. It lasts for a few days
4. Antibodies are obtained from outside.
5. At times the body reacts to the introduction of antisera. It is called serum sickness.