A B-cell is a type of blood cell. B-cells belong to a group of white blood cells (WBCs) called lymphocytes. WBCs protect the body from infection.
The main job of B-cells is to fight infection. B-cells get activated when an infection occurs and they produce molecules called antibodies that attach to the surface of the infectious agent. These antibodies either kill the infection causing organism or make it prone to attack by other WBCs. They play a major role in the immune system, which guards the body against infection.
They are called B-cells because they are both created and matured in the bone marrow. After maturation, B-cells are present in the blood and in lymph nodes.
B-cells may be affected in some rare diseases of the immune system and in cancers, like lymphoma.