The primary function of dendritic cells in the immune response is to act as antigen-presenting cells. They capture, process, and present antigens from pathogens to T cells, thereby initiating an adaptive immune response. Dendritic cells are found in tissues such as the skin and mucosal surfaces, where they encounter potential threats. Their role is critical for the activation of naive T cells and promoting immunological memory, thus playing an essential part in long-term immunity.