At what point do helper T-cells differentiate into either TH1 or TH2 cells during an immune response?

• A. After encountering specific cytokine signals from antigen-presenting cells
• B. Immediately after leaving the bone marrow
• C. During their maturation in the thymus
• D. Only after they have produced antibodies

Answer: (A)

Verified step by step guidance

1. Understand the role of helper T-cells (CD4+ T-cells) in the immune system. These cells are crucial for coordinating immune responses by activating other immune cells, such as B-cells and cytotoxic T-cells.
2. Recognize that helper T-cells differentiate into subsets (TH1 or TH2) based on the cytokine signals they receive. TH1 cells are involved in cell-mediated immunity, while TH2 cells are associated with humoral immunity.
3. Learn that helper T-cells are initially naive when they leave the thymus and do not differentiate into TH1 or TH2 cells during their maturation in the thymus. Their differentiation occurs later in the immune response.
4. Identify the role of antigen-presenting cells (APCs), such as dendritic cells and macrophages, in the immune response. APCs present antigens to naive helper T-cells and release specific cytokines that guide their differentiation into TH1 or TH2 cells.
5. Conclude that helper T-cells differentiate into TH1 or TH2 cells only after encountering specific cytokine signals from APCs during an immune response, not immediately after leaving the bone marrow or after producing antibodies.