Which of the following best describes the primary difference between memory T cells and cytotoxic T cells?

• A. Memory T cells persist long-term after an infection to provide a faster response upon re-exposure, while cytotoxic T cells directly kill infected or abnormal cells during the initial immune response.
• B. Memory T cells produce antibodies, whereas cytotoxic T cells activate B cells.
• C. Memory T cells are only found in the thymus, while cytotoxic T cells circulate in the bloodstream.
• D. Memory T cells are responsible for phagocytosis, while cytotoxic T cells release histamine.

Answer: (A)

Verified step by step guidance

1. Understand the role of T cells in the immune system: T cells are a type of lymphocyte that play a central role in adaptive immunity. They are divided into different types based on their function, including memory T cells and cytotoxic T cells.
2. Define memory T cells: Memory T cells are long-lived cells that remain in the body after an infection has been cleared. Their primary function is to 'remember' the pathogen and provide a faster and more efficient immune response upon re-exposure to the same pathogen.
3. Define cytotoxic T cells: Cytotoxic T cells, also known as CD8+ T cells, are responsible for directly killing infected cells, cancerous cells, or cells that are otherwise abnormal during the initial immune response. They release enzymes like perforin and granzymes to induce apoptosis in target cells.
4. Compare the functions of memory T cells and cytotoxic T cells: Memory T cells are involved in long-term immunity and do not directly kill infected cells. Instead, they ensure a rapid response upon re-exposure to the pathogen. Cytotoxic T cells, on the other hand, are active during the initial immune response and directly kill infected or abnormal cells.
5. Eliminate incorrect options: Memory T cells do not produce antibodies (this is the role of B cells), are not limited to the thymus (they circulate in the body), and are not responsible for phagocytosis or histamine release. Cytotoxic T cells do not activate B cells or release histamine; their primary role is cell-mediated killing.