What are the primary functions of dendritic cells in initiating adaptive immunity?

• A. Capture antigen, mature, migrate to lymph nodes, present antigen with co-stimulation to naive T cells, and secrete cytokines to direct T cell differentiation.
• B. Produce antibodies against pathogens.
• C. Directly kill infected cells through cytotoxic mechanisms.
• D. Differentiate into plasma cells to secrete antibodies.

Answer: (A)

Dendritic cells serve as the professional bridge between innate detection and adaptive immunity. They capture antigen in tissues, undergo maturation to upregulate MHC and co-stimulatory molecules, and migrate to draining lymph nodes. In the lymph node, they present processed peptide on MHC to naive T cells and provide essential co-stimulation (such as B7 engaging CD28), which together fully activate the T cells. They also secrete cytokines that shape T cell differentiation into specific helper lineages, guiding the direction of the adaptive response. This combination—antigen capture, maturation with co-stimulatory signals, migration to lymph nodes, presentation to naive T cells, and cytokine-driven differentiation—best explains how dendritic cells initiate adaptive immunity. Antibody production and antibody-secreting plasma cells come from B cells, while cytotoxic killing is the role of cytotoxic T cells, not the initiating function of dendritic cells.