[It] serves as a holding tank for ready-to-go immune agents called monocytes. . . the spleen is their main dispatcher. . . . It recycles iron from old red blood cells, houses fresh blood cells, synthesizes antibodies and acts as a chamber in which pathogens are killed. . . .
In 1977, scientists reported that servicemen who had undergone spleen removal during World War II had higher rates of death due to diseases in general — and from heart disease and pneumonia specifically — during the 28 years following the war, compared with similar men who kept their spleens. . . .
Spleen removal can . . . cause diminished response to some vaccines and increased susceptibility to infections.
Spleen malfunction may be one factor in autoimmune diseases.