What Does the Spleen Do?

The spleen helps with immune function.

The spleen is an oval-shaped organ that sits under the rib cage on the left-hand side of the body. It is the size of a human fist. The function of spleen is to make new red blood cells and destroy old cells. It plays an important role- in the body’s defense against infection. The spleen contains two main regions of tissue called white pulp and red pulp.

• Red pulp: Contains cavities filled with blood and tissues containing red blood cells and white blood cells.
• White pulp: This mostly consists of white blood cells (T cells and B cells) that have a role in immunity.

The role of spleen in the body includes

• Blood filter: The spleen's main function is to act as a filter for the blood. It recognizes and removes old, malformed or damaged red blood cells. When blood flows into the spleen, it performs "quality control"; blood cells may need to pass through a maze of narrow passages. Healthy blood cells simply pass through the spleen and continue to circulate throughout the bloodstream. Blood cells that can't pass the test will be broken down in the spleen by special cells called macrophages.
• Defence system: The spleen also plays an important part in the body’s immune system. It can recognize and destroy specific bacteria (Hemophilus, Nisseria) that have a capsule.
• Economical function: The spleen recycles the useful components like iron from the old cells. It stores iron in the form of ferritin or bilirubin, and eventually returns the iron to the bone marrow, where hemoglobin is made. Hemoglobin is an important protein in the blood that transports oxygen from the lungs to all parts of the body.
• Reserve system: The spleen is a backup for storing blood. The blood vessels in the spleen are able to get wider or narrower, depending on the body's needs. When vessels are expanded, the spleen can actually hold up to a cup of reserve blood. If for any reason the body needs some extra blood (during severe injury), the spleen may respond by releasing that reserve blood back into the system.
• Production: The spleen also produces compounds called opsonins that help with immune function.
• Help during development: Before the birth of a baby, the spleen works to produce the baby's red blood cells. It gradually stops this before the birth and the bone marrow takes over.

Yes, it is possible to live without a spleen. However, its absence may make a person susceptible to serious infections. 

One of the functions of the spleen is to fight off certain bacteria like Streptococcus pneumoniae, Neisseria meningitidis and Hemophilus influenzae. Removal of the spleen lowers a person’s resistance to these infections. Ideally, people must be vaccinated against these bacteria about two weeks before a planned operation or up to two weeks after emergency spleen removal. The doctor may recommend other vaccines as well.

Usually when the spleen is removed, other organs such the liver can take up most of the functions of the spleen (like destruction of old blood cells). The spleen plays an important role in the protection from certain bacteria. Overwhelming post-splenectomy infections (OPSI) is the term for serious infections that may arise after spleen removal. Children  under the age of five and those who have had their spleen removed in the past two years are at a highest risk for developing these infections.

Children whose spleen has been removed often need to take antibiotics every day to prevent these infections. Adults usually do not need daily antibiotics unless they become sick or there is a chance that they could become sick. People who have had their spleen removed should carry antibiotics with them in case they plan on traveling out of the country. They should start taking antibiotics as soon as they feel sick. People who have had their spleen removed should ask their doctor about getting required vaccinations and flu shots.