The spleen plays an important role in the body's immune system, helping protect it against infections. It also acts as a sort of filter for the blood stream, helping to remove old blood cells and platelets from the circulation.
There are a few different reasons that a spleen may be removed. It is commonly removed as a result of damage due to a traumatic accident to help prevent further bleeding
. In certain types of congenital blood disorders, the spleen may actually cause hemolysis (or destruction) of blood cells and removal may help prevent against severe anemia
. The spleen may also be a part of an acquired autoimmune disease in which the body attacks its own blood cells and platelets; removal of the spleen is often an integral part of treatment if other measures (such as steroids) do not completely solve the problem.
People without spleens need to take special care to make sure their vaccinations are up-to-date, as the absence of the spleen makes patients more susceptible to certain types of infection (typically those caused by encapsulated organisms). For this reason, it is extremely important to be vaccinated against meningococcus (the cause of meningitis), Haemophilus influenza type B, and pneumococcus (a common cause of pneumonia