Which type of T cell plays an integral role in both humoral and cell-mediated immunity?

• A. Memory T cell
• B. Helper T cell (CD4+)
• C. Regulatory T cell
• D. Cytotoxic T cell (CD8+)

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the role of T cells in the immune system. T cells are a type of lymphocyte that play a critical role in adaptive immunity. They are divided into different types based on their function, including Helper T cells (CD4+), Cytotoxic T cells (CD8+), Regulatory T cells, and Memory T cells.
2. Step 2: Learn about humoral immunity. Humoral immunity involves the production of antibodies by B cells, which are activated by signals from Helper T cells (CD4+). These signals are essential for B cell activation and antibody production.
3. Step 3: Learn about cell-mediated immunity. Cell-mediated immunity involves the activation of Cytotoxic T cells (CD8+) and other immune cells to directly attack infected or abnormal cells. Helper T cells (CD4+) play a key role in this process by releasing cytokines that stimulate and coordinate the activity of Cytotoxic T cells and macrophages.
4. Step 4: Recognize the integral role of Helper T cells (CD4+). Helper T cells are central to both humoral and cell-mediated immunity because they provide the necessary signals (via cytokines) to activate B cells, Cytotoxic T cells, and other immune cells.
5. Step 5: Compare the functions of other T cell types. Memory T cells are involved in long-term immunity, Regulatory T cells help suppress immune responses to prevent autoimmunity, and Cytotoxic T cells directly kill infected or abnormal cells. None of these types play the same coordinating role in both humoral and cell-mediated immunity as Helper T cells.