The spleen is an organ that is located just under the lungs on the left side of the body.

Structure

The spleen can be split into two components that perform two very different roles:

Red pulp: responsible for the removal of red blood cells that have reached the end of their useful lifespan from the bloodstream

White pulp: serves as a repository for lymphoid cells such as T cells and B cells. Here cells are exposed to a constant flow of antigen from the bloodstream. T cells tend to be positioned around the blood vessels of the spleen, whereas B cells form a sheath around the lymphatic vessels. his means that the B cells are ready and poised to produce antibodies as quickly as possible in response to matching antigen.

Spleen absence and loss of function

Some people are born without spleens and some people lose them as a result of trauma or injury. People without spleens are at a much higher risk of developing life-threatening infections and as a result are often place on a life long prophylactic regimen of antibiotics. This is due to a reduced individual capacity to produce antibodies and activate certain classes of immune cells.