The clonal selection theory states that:

• A. Self-reacting T cells are destroyed in the bone marrow.
• B. B cells will only proliferate during an infection if their BCRs successfully bind to the pathogen.
• C. Antibody structure changes as it encounters an antigen for higher specificity binding.
• D. Each T cell produces many different types of antibodies.

Answer: (B)

Verified step by step guidance

1. Understand the clonal selection theory, which is a fundamental concept in immunology explaining how specific immune cells are activated and proliferate in response to an antigen.
2. Recognize that B cells and T cells are types of lymphocytes involved in the adaptive immune response. B cells are responsible for producing antibodies, while T cells have various roles including helping B cells and directly killing infected cells.
3. Identify that the clonal selection theory involves the selection and proliferation of specific B cells. This occurs when B cell receptors (BCRs) on the surface of B cells bind to a specific antigen, leading to the activation and proliferation of those B cells.
4. Note that the statement 'B cells will only proliferate during an infection if their BCRs successfully bind to the pathogen' aligns with the clonal selection theory. This is because only B cells with receptors specific to the pathogen will be selected to proliferate and produce antibodies.
5. Clarify that the other statements are incorrect: Self-reacting T cells are typically destroyed in the thymus, not the bone marrow; antibody structure does not change upon encountering an antigen, but rather, the diversity of antibodies is generated through genetic recombination; each T cell does not produce antibodies, as this is the role of B cells.