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B Cells1

B cells (B-lymphocytes) mature into plasma cells which make antibodies, highly specialized blood proteins also know as immunoglobulins. Antibodies attach themselves to invading pathogens and set off a complex chain reaction involving other components of the immune system which ultimately leads to the destruction and removal of the invading pathogen.

Each B cell makes a unique antibody that has the ability to recognize a specific part of the invading pathogen. When activated, B cells can mature into plasma cells which make large quantities of antibody that can be released into the blood.

There are five main types of antibodies:

IgM

The first antibody type to be made by B cells in response to an invading pathogen, this antibody offers important protection during the early days of infection. IgM tends to stay in the bloodstream, where it aids in killing bacteria.

IgD

IgD antibody may be present on the surface of B cells with IgM.

IgG

The next type of antibody to be made after IgM, IgG antibodies are formed in large quantities and work in the blood and tissues of the body. They bind to microorganisms like bacteria so that the immune cells (for example macrophage) have an easier time recognizing and ingesting them. IgG antibodies are also important for activating the complement system which leads to destruction of the bacteria. IgG antibodies are the only type that can pass from a mother to her unborn baby through the placenta.

IgA

Produced along the surface linings of the lungs and intestines, this antibody is secreted in body fluids such as tears, saliva, and mucus. IgA also protects against infection in the respiratory tract and intestines. IgA passes from mothers to newborns through breast milk.

IgE

IgE antibodies are normally present in trace amounts and are important in allergic reactions.

  1. Blaese RM, Winkelstein J. Patient & Family Handbook for Primary Immunodeficiency Diseases. Towson, MD: Immune Deficiency Foundation; 2007, p.2.