The spleen produce antibodies in its white pulp, removing from the circulation antibody-coated bacteria and antibody-coated blood cells. It contains in reserve half the body's monocytes in its red pulp that upon moving to injured tissue such as the heart turn into dendritic cells and macrophages and aid wound healing. It is one of the centers of activity of the reticuloendothelial system, and can be considered analogous to a large lymph node. The absence of the spleen can lead to a predisposition to certain infections.
The spleen is present in most vertebrates and lie in the abdominal cavity. It is an important part of the blood-forming system. It is also one of the largest lymphoid organs in the body and is involved in the defenses against diseases attributed to the reticuloendothelial system.