Describe of how the bacillus calmette-guerin vaccine gives immunity
The Bacillus Calmette-Guerin (BCG) vaccine is a live attenuated strain of Mycobacterium bovis, a bacterium closely related to Mycobacterium tuberculosis, the causative agent of tuberculosis. When the BCG vaccine is administered, the attenuated bacteria grow within the body and stimulate an immune response.
The immune system recognizes the BCG bacteria as foreign and mounts a robust immune response, primarily involving the activation of T cells and production of specific antibodies. This immune response not only targets the BCG bacteria but also provides cross-protection against related Mycobacterium species, including M. tuberculosis.
Over time, the immune system forms a memory of the BCG bacteria, which allows for a faster and more effective response upon subsequent exposure to M. tuberculosis. This memory response can help prevent the development of active tuberculosis disease by controlling the spread of the bacteria and reducing the severity of the infection.
In summary, the BCG vaccine provides immunity against tuberculosis by stimulating the immune system to recognize and respond to the bacteria, thereby preventing or reducing the severity of tuberculosis infection.