In the context of the immune system, what is a naive lymphocyte?

• A. A lymphocyte that has undergone clonal expansion
• B. A lymphocyte that has been activated and is producing antibodies
• C. A lymphocyte that has not yet encountered an antigen
• D. A lymphocyte that is part of the innate immune response

Answer: (C)

Verified step by step guidance

1. Understand the role of lymphocytes in the immune system: Lymphocytes are a type of white blood cell that play a crucial role in the adaptive immune response. They include B cells and T cells, which are responsible for recognizing specific antigens and mounting an immune response.
2. Define 'naive lymphocyte': A naive lymphocyte is a lymphocyte that has not yet encountered its specific antigen. It is in a resting state, waiting to be activated by the presence of an antigen.
3. Differentiate between naive and activated lymphocytes: Once a naive lymphocyte encounters its specific antigen, it becomes activated. This activation leads to clonal expansion, where the lymphocyte proliferates and differentiates into effector cells that can combat the antigen.
4. Clarify the term 'clonal expansion': Clonal expansion is the process by which an activated lymphocyte divides and produces many copies of itself. This is crucial for mounting an effective immune response, as it increases the number of cells that can recognize and respond to the antigen.
5. Explain why a naive lymphocyte is not part of the innate immune response: The innate immune response is the body's first line of defense and is non-specific. Naive lymphocytes are part of the adaptive immune response, which is specific and involves the recognition of specific antigens.