What role do dendritic cells play in T cell selection?

• A. They promote T cell maturation
• B. They provide costimulatory signals
• C. They present antigens for negative selection
• D. They destroy unfit T cells

Answer: (C)

Dendritic cells play a critical role in the process of T cell selection by presenting antigens to T cells, particularly during negative selection. This process occurs primarily in the thymus, where immature T cells, or thymocytes, undergo a selection process to ensure that only those with appropriate affinity for self-antigens survive, while those that strongly react to self-antigens are induced to undergo apoptosis, or programmed cell death.

By presenting self-antigens in a context that can trigger negative selection, dendritic cells help to eliminate potentially autoreactive T cells that could lead to autoimmune diseases. This presentation is crucial for maintaining tolerance to self, thereby helping the immune system distinguish between self and non-self.

The other roles mentioned in the options involve different mechanisms or cells within the immune response. For instance, while costimulatory signals are important for T cell activation, these signals are typically provided by dendritic cells as part of activating T cells rather than during the negative selection process. Additionally, promoting T cell maturation and destroying unfit T cells are not the primary functions of dendritic cells in the context of selection; instead, maturation occurs through interactions with various signals within the thymus, and the elimination of unfit T cells is a consequence of the selection process