B-Cells in Your Immune System

How B-Lymphocytes Work in Your Immune System

B-cells
B-cells. Science Picture Co Collection Mix: Subjects/Getty Images

Definition of B-Cells

The B-cell, also called B-lymphocyte, is a type of white blood cell that plays a large role in protecting your body from infection. Without B-cells, your body would not be as effective at fighting off a number of very 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 spongey 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 in 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 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.

What Do B-Cells Do in a Healthy Body?

The main 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 the flares over a battle site, if you will; 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 Do 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 transforms into a plasma B-cell, whose specialized job it is to mass-produce the antibodies that match the activating invader.

– "A functional plasma cell produces up to 10,000 antibodies per second to release them into the blood stream."

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 or bacteria 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.

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

A Word From Verywell: Disorders of B-Lymphocytes

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, however the exact cell that becomes cancerous may be more mature or more immature; in other words, the cell that gives rise to the 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.

Sources:

Minnich M, Tagoh H, Bönelt P, et al. Multifunctional role of the transcription factor Blimp-1 in coordinating plasma cell differentiation. Nat Immunol. 2016 Mar;17(3):331-43.

Julie Tellier, Wei Shi, Martina Minnich, Yang Liao, Simon Crawford, Gordon K Smyth, Axel Kallies, Meinrad Busslinger, Stephen L Nutt. Blimp-1 controls plasma cell function through the regulation of immunoglobulin secretion and the unfolded protein response. Nat Immunol. 2016;17(3): 323–330.

B Cells and Antibodies, Molecular Biology of the Cell. 4th edition. Copyright 2002, Bruce Alberts, et. al.

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