Some phagocytes also have the ability to present antigen to lymphocytes. Important phagocytes are monocytes and macrophages. Macrophages are seeded throughout body tissues in a variety of guises. Specialized macrophages include alveolar macrophages in the lungs, mesangial phagocytes in the kidneys, microglial cells in the brain, and Kupffer cells in the liver.
Macrophages are versatile cells that play many roles.
As scavengers, they rid the body of worn-out cells and other debris. Macrophages are not the only cells to present antigen to lymphocytes. Other antigen-presenting cells include B cells, as noted above, and dendritic cells , irregularly shaped white blood cells found in the spleen and other lymphoid organs. Dendritic cells typically have long threadlike tentacles that enmesh lymphocytes and antigens. Langerhans cells are dendritic cells that travel about in the skin, picking up antigen and transporting it to nearby lymph nodes.