Which function best describes dendritic cells in initiating adaptive immunity?

• A. They capture, process, and present antigens to naive T cells, providing costimulation to activate T cells.
• B. They secrete antibodies that neutralize pathogens.
• C. They phagocytose pathogens without antigen presentation.
• D. They stimulate mast cells to release mediators.

Answer: (C)

Dendritic cells act as professional antigen-presenting cells that bridge innate and adaptive immunity. They patrol tissues, capture and process pathogens, and then migrate to lymph nodes where they present processed antigen on MHC molecules to naive T cells. Crucially, they provide costimulatory signals (for example, B7 family molecules engaging CD28 on T cells) in addition to the antigen-MHC complex. Without this second signal, T cells may become anergic, so the combination of antigen presentation plus costimulation is what truly activates naive T cells and kick-starts the adaptive immune response.

Secreting antibodies is a function of B cells and plasma cells, not dendritic cells. While dendritic cells can phagocytose pathogens, their key role in initiating adaptive immunity is presenting antigen to T cells with the necessary costimulatory cues. They do not primarily stimulate mast cells to release mediators; that process is more associated with immediate hypersensitivity pathways involving mast cells and basophils.