Illustration of dendritic cells (purple), key components of the immune system, which ingest and display foreign matter antigens on their surface, and interact with other cells in the immune response, such as B cells and killer "T" cells (in blue). The dendritic cell may be on of the key cells involved in the detection and subsequent destruction of bacteria in infected tissue, as well as initiating the killer T cell attack on cancerous tumors (shown here, center).