Immunoglobulins, also referred to as antibodies, are proteins that are located in the bodily fluids and blood of vertebrates that regulate the immune system. These immunoglobulins help to identify foreign objects to neutralize them. Some examples of foreign objects in the blood stream are viruses and bacteria. Immunoglobulins are created by a white blood cell called a plasma cell. Immunoglobulins fall into five classes based on their antigenic properties.
Immunoglobulins are also called antibodies. They are proteins that vertebrates use to regulate the immune system and defend against infectious agents. IgA is the primary antibody in the membranes of the respiratory and gastrointestinal tract, as well as other locations in the body. IgD is secreted by B cells to act as a receptor for antigens (foreign agents). IgE is especially present in mucous membranes and the skin, and is the primary antibody responsible for allergic responses, as well as parasitic infections. IgG is the body’s main defense against bacteria, and makes up 75 percent of all human immunoglobulins. IgM fights blood infections and is the first antibody produced by fetuses.
Immunoglobulin A is the major antibody found in the membranes of the respiratory and gastrointestinal tract. The second most common immunoglobulin in the human body, IgA can also be found in tears, saliva, mucus, and colostrum. IgA is one of the most important immunoglobulins in local immunity. The two subclasses of IgA are IgA1 and IgA2.
This immunoglobulin class is present in tiny amounts in blood serum. Immunoglobulin D is present on B cell surfaces and it is used as a receptor for antigens. It helps to anchor them to cell membranes with its abundance of amino acids. It is not completely determined why IgD is found in serum, making this the least understood antibody.
Immunoglobulin E can be found protecting the body in the mucous membranes and skin. IgE is the least common antibody found in the bloodstream. It triggers allergic reactions, which occur when IgE binds to cells to which the body is allergic. IgE also defends the body during parasitic infections; sometimes doctors measure the amount of IgE in the blood to diagnose parasitic infections.
This major class of immunoglobulins is the body’s main defense against bacteria. IgG makes up around 75 percent of all human immunoglobulins and is the only class that can cross into the placenta to protect newborns against infections. Immunoglobulin G is the most versatile of all the antibodies because it can carry out the functions of the other types of antibodies as well. The four subclasses of IgG are IgG1, IgG2, IgG3, IgG4.
These immunoglobulins fight blood infections and help to trigger additional production of immunoglobulin G. Like IgD, these antibodies are present on lymphocyte B cells. Of all immunoglobulins, 10 percent are IgM. Immunoglobulin M is the first antibody produced by fetuses. These immunoglobulins are well-suited for clumping microorganisms and helping them to be removed from the body.
