Final answer:
Naive cytotoxic and helper T cells interact with foreign antigens presented by dendritic cells primarily within lymph nodes, which are secondary lymphoid organs essential for T cell activation.
Step-by-step explanation:
Normally, naive cytotoxic and helper T cells interact for the first time with foreign antigens presented by dendritic cells within the lymph nodes. This location is one of the secondary lymphoid organs where naive T cells encounter and respond to antigens. Dendritic cells, along with macrophages and B cells, play a crucial role in presenting these antigens to T cells. These antigen-presenting cells (APCs) perform their functions in regions known as draining lymph nodes, which are pivotal for most T cell responses against pathogens present in the interstitial tissues. Naive T cells migrate from their site of maturation in the thymus to these secondary lymphoid organs, where they become activated upon encountering specific antigens.