Do you mean "Spleen?"
If so, your spleen is the organ in the upper left part of your abdomen that is an integral part of your immune system. Basically, it has two functions:
1) It acts as a filter to removes old or dysfunctional red blood cells.
2) As the blood in the body is filtered in the spleen, the spleen also has a reserve of immune cells that synthesize antibodies from the antigens circulating in the blood.