Which cells are primarily involved in negative selection in the thymus?

• A. T cells
• B. B cells
• C. Dendritic cells
• D. Macrophages

Answer: (C)

Negative selection in the thymus is a crucial process for ensuring that T cells mature correctly and do not react excessively to self-antigens. During this process, thymocytes, which are developing T cells, are tested for their affinity to self-antigens presented by host cells. Dendritic cells play a significant role in this selection process because they are adept at presenting these self-antigens.

When thymocytes express T-cell receptors (TCRs) that strongly bind to the self-antigens presented by dendritic cells, they receive signals leading to apoptosis, or programmed cell death. This helps to eliminate potentially autoreactive T cells, thereby preventing autoimmune diseases. The influence of dendritic cells on the negative selection process is vital, as they help maintain the self-tolerance of the immune system, ensuring that T cells can effectively respond to foreign antigens without attacking the body’s own tissues.

Other cell types such as macrophages and thymic epithelial cells also contribute to thymocyte development; however, dendritic cells are particularly crucial for presenting the necessary self-antigens needed for negative selection.