B-Cells in Your Immune System

The B-cell, also called B-lymphocyte, is a type of white blood cell that plays a significant role in protecting your body from infection.

Without B-cells, your body would not be as effective at fighting off a number of common bacteria and viruses; and you would lack the long-lasting "memory antibody" function that is typical after recovering from an infection or after being immunized against a specific infectious invader.


B-cells, like other white blood cells, arise from hematopoietic stem cells that reside within the spongy bone marrow, especially in certain bones like the hip bone and vertebrae. These blood-forming cells give rise to B-cells through a series of steps. After they mature, B-cells are present in your blood and certain parts of your body such as in your lymph nodes.

There are two main types of lymphocytes: T-cells and B-cells. When you have a complete blood count (CBC) blood test done, in the laboratory report you get a run-down of the different types of blood cells and percentages, including lymphocytes, but there is no differentiation as to which lymphocytes are T-cells and which are B-cells.

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B-Cell Functions

The primary responsibility of B-cells involves the body's response to foreign invaders through what is known as humoral immunity. B-cells become "activated" when they encounter foreign antigens, as in foreign markers on the outside of bacteria cells during an infection.

In response to such an infection, B-cells can differentiate into plasma cells—the body's antibody-producing factories. Plasma cells produce large proteins called immunoglobulins, or antibodies that attach to the surface of foreign agents.

These antibodies serve as flags or flares over a battle site. They recruit other defensive molecules in the bloodstream to the site, working toward killing the infection-causing organism. They also signal other immune cells to, in turn, wage war on the invader.

They play a major role in the immune system, which guards the body against infection. This part of immunity that is heavily dependent on antibodies is referred to as humoral immunity. The counterpart to humoral immunity is cell-mediated immunity.

How B-Cells Give Us Immunity

A young B-cell, called a naive B-cell, circulates in the bloodstream, usually ending up in the spleen or lymph nodes. It gets activated by an antigen, which can be any substance the body thinks is foreign, such as a piece of a virus, or a patch of a bacterium's cutter capsule. T-cells are often involved in this process.

The B-cell begins to transform into a plasma B-cell, whose specialized job it is to mass-produce the antibodies that match the activating invader—up to 10,000 antibodies per second.

Each plasma B-cell makes antibodies to only one antigen. They are very specific. Luckily, there are millions of them in our body so we can fight many different types of infection. Throughout the life of a B-cell, it makes these antibodies. They settle down mostly in the spleen and lymph nodes to pump out antibodies.

Some of the activated B-cells become memory B-cells, which have very long lives in the bone marrow, lymph nodes, and spleen. They remember the antigen they are specific for and are ready to respond quickly if they see it again. These are the cells that give us long-lasting immunity to different invaders.

When you get immunized, the vaccine contains antigens that stimulate the B-cells to produce antibodies that will then attack the virus, bacteria, or toxin you are being immunized against. This mimics what is happening in your body when you are infected with that germ, but without the same risks of the disease caused by the germ or toxin.

Because B-cells have long memories, they can produce antibodies against germs and toxins for months and years, giving you a period of immunity.

Associated Conditions

Sometimes plasma B-cells produce antibodies to antigens that are on our own cells or autoantibodies, and this can be a component of various autoimmune diseases, such as rheumatoid arthritis, lupus, multiple sclerosis, and type 1 diabetes. These are instances of the immune system attacking healthy tissues to produce a disease.

B-cells may be malignantly transformed into chronic lymphocytic leukemia, acute lymphoblastic leukemia, and certain types of lymphoma. These diseases are essentially B-cell cancers.

The exact cell that becomes cancerous may be more mature or more immature. The cell that gives rise to cancer may be closer in form and function to an actual B-cell, versus more closely resembling an immature blood-forming cell that would eventually give rise to an adult B cell, if healthy.

2 Sources
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  1. Ellebedy AH, Jackson KJ, Kissick HT, et al. Defining antigen-specific plasmablast and memory B cell subsets in human blood after viral infection or vaccination. Nat Immunol. 2016;17(10):1226-34. doi:10.1038/ni.3533

  2. Rawlings DJ, Metzler G, Wray-dutra M, Jackson SW. Altered B cell signalling in autoimmunity. Nat Rev Immunol. 2017;17(7):421-436. doi:10.1038/nri.2017.24

Additional Reading

By Indranil Mallick, MD
 Indranil Mallick, MD, DNB, is a radiation oncologist with a special interest in lymphoma.