What are the antigen-presenting cells of the immune system?
The antigen-presenting cells of the immune system, also called as APC cells, are cells that do phagocytosis and digestion of foreign (to the body) microorganisms and later expose antigens derived from these microorganisms in the outer side of their plasma membrane. These processed antigens are then recognized by lymphocytes that activate the immune response. Various types of cells, as the macrophages, can act as antigen-presenting cells.
The Immune System - Image Diversity: antigen-presenting cells