Dendritic immune cells. Fluorescent deconvolution light micrograph of a section through dendritic cells (red) in the epidermis (outermost layer of skin). Dendritic cells are antigen-presenting cells (APCs, or accessory cells) of the mammalian immune system. APCs recognise and phagocytose (engulf and destroy) pathogens. They then present the digested parts (antigens) of the phagocytosed pathogens to other immune system cells. The antigen is recognised by helper T lymphocytes, which secrete chemicals such as cytokines to activate other immune cells against the pathogen, including T cytotoxic cells and antibody-producing B cells. Magnification: x400, when printed 10 cm wide.