How are B and T cells capable of responding to antigens before they enter the body?

• A. Genetic mutation
• B. Genetic recombination
• C. Cell division
• D. Immune memory

Answer: (B)

B and T cells can respond to antigens due to a process known as genetic recombination, which occurs during their development in the bone marrow and thymus, respectively. This biological mechanism allows for the extensive diversity of antigen receptors on the surface of B and T cells.

During genetic recombination, specific segments of DNA that encode the receptors for antigens are rearranged, leading to the formation of a unique receptor for each individual lymphocyte. This process ensures that each B and T cell can potentially recognize different antigens, even before the body is exposed to them. As a result, when a pathogen or foreign antigen enters the body, those lymphocytes that possess the corresponding receptors are primed and ready to mount an immune response.

This diversity in receptors is crucial for the adaptive immune system because it allows for the recognition of a vast array of pathogens, ensuring the body can effectively respond to new and emerging threats. By equipping B and T cells with a variety of receptors, genetic recombination plays a pivotal role in the immune system's ability to recognize and respond to diverse antigens.