Which of the following is primarily associated with cell-mediated immunity?

• A. Production of immunoglobulins by plasma cells
• B. Neutralization of pathogens by antibodies
• C. Activation of cytotoxic T lymphocytes to destroy infected cells
• D. Opsonization of bacteria for phagocytosis

Answer: (C)

Verified step by step guidance

1. Understand that the immune system has two main branches: humoral immunity and cell-mediated immunity. Humoral immunity primarily involves antibodies produced by B cells, while cell-mediated immunity involves T cells acting directly on infected or abnormal cells.
2. Identify the key players in humoral immunity: plasma cells produce immunoglobulins (antibodies), which neutralize pathogens and opsonize bacteria to enhance phagocytosis. These functions are antibody-mediated and thus part of humoral immunity.
3. Recognize that cell-mediated immunity does not rely on antibodies but on T lymphocytes, especially cytotoxic T cells, which directly kill infected or abnormal cells by recognizing antigen presented on their surface.
4. Match each option to the correct branch of immunity: production of immunoglobulins and neutralization of pathogens by antibodies are humoral; opsonization is also antibody-mediated; activation of cytotoxic T lymphocytes is a hallmark of cell-mediated immunity.
5. Conclude that the option 'Activation of cytotoxic T lymphocytes to destroy infected cells' is primarily associated with cell-mediated immunity because it involves T cell responses rather than antibody functions.