91Ó°ÊÓ

The human immune system is distinguished into two types based on their response: innate and adaptive immune systems.

Innate immunity is present by birth which is not specific. The response of the innate immune system is common for all invaders. In contrast, the adaptive immune system is specific and activated after the entry of antigens.

Sir Macfarlane Burnet proposed the clonal selection theory. The postulates of the theory have become the foundation for modern immunology.

The theory states that the encounter of antigens does not induce antibodies. They are already present in the body in a limitless number. The effector cells are derived when receptors of antigens bind with the lymphocytes.

The environmental challenges induce the greater or lesser use of certain organs. The change brought in the organs is acquired in the next generation. Continued use of organs makes them strong and heritable. The disuse of organs makes them inactive and reduces or disappears in the next generation.

Challenges and acquiring the requirements are common in both clonal selection and Lamarck’s theory. The characters that are required for acquisition are already present in an individual genome.

Therefore, heritable differences induce specific immune systems in the body. An encounter of challenges activates antibodies that are already present in the body. In the same way, the challenges of the environment activate certain parts of the body, which helps the organ adapt as per the challenge.