Which immune response cell type specifically activates B and T lymphocytes?

• A. B cells
• B. Cytotoxic T cells
• C. Helper T cells
• D. Natural Killer cells

Answer: (C)

Helper T cells play a crucial role in the adaptive immune response by specifically activating both B and T lymphocytes. They do this through several mechanisms, primarily by releasing cytokines, which are signaling molecules that enhance the immune response. When Helper T cells encounter an antigen presented by an antigen-presenting cell (such as a dendritic cell), they become activated and secrete cytokines. These cytokines stimulate B cells to produce antibodies and enhance the activation and proliferation of cytotoxic T cells.

In contrast, other cell types mentioned, such as B cells and cytotoxic T cells, do not have the same role in activating other immune cells. B cells are primarily responsible for producing antibodies and can be activated under the influence of Helper T cells but do not themselves activate T or B lymphocytes. Cytotoxic T cells are focused on killing infected or cancerous cells rather than activating other immune cells. Natural Killer cells are part of the innate immune response and primarily target virus-infected or tumor cells without the need for prior activation by Helper T cells.

Therefore, Helper T cells are essential for orchestrating the broader adaptive immune response, making them the key immune response cell type that activates both B and T lymphocytes.