In doing research on this vital organ, I’ve found several great sites:
The spleen governs the flow of blood and lymph fluids in the body. It is where the blood and lymph systems come together and party while cleaning house. Old, dead blood cells are removed from the blood system and are carried away by the lymph system. The amount of blood flow is regulated by the spleen, and it can hold blood while it removes old blood cells and picks out any unwelcome micro-organisms (like bacteria or viruses). The spleen and lymph system create lymphocytes which kill those unwanted micro-organisms off.
[The spleen is an] important organ for antibacterial and antifungal immune reactivity. —http://www.ncbi.nlm.nih.gov/pubmed/16056254