Any of several classes of structurally related proteins in the blood serum, produced by plasma cells as an immune response against foreign agents (antigens).
IgG is the most abundant of the five classes of immunoglobulins. Its normal mean serum concentration is 1240 mg/dl. It is the major antibody in the secondary humoral response of immunity, serves to activate the complement system, and is frequently involved in opsonization. IgG is the only immunoglobulin that crosses the placenta and is the major component of passive maternal antibody transfer via colostrum and yolk. IgM is the first antibody produced in the primary immune response. a protein of animal origin with known antibody activity. Immunoglobulins are major components of what is called the humoral immune response system. They are synthesized by lymphocytes and plasma cells and found in the serum and in other body fluids and tissues, including the urine, spinal fluid, lymph nodes, and spleen. IgG is the only immunoglobulin that crosses the placenta and is the major component of passive maternal antibody transfer via colostrum and yolk. IgM is the first antibody produced in the primary immune response. Definition of IGG. 1. : a class of immunoglobulins including the most common antibodies circulating in the blood that facilitate the phagocytic destruction of microorganisms foreign to the body, that bind to and activate complement, and that are the only immunoglobulins to cross over the placenta from mother to fetus. 1. : a class of immunoglobulins that include the most common antibodies circulating in the blood, that facilitate the phagocytic destruction of microorganisms foreign to the body, that bind to and activate complement, and that are the only immunoglobulins to cross over the placenta from mother to fetus. 2. Immunoglobulin A: A major class of immunoglobulins (antibodies) found in serum and external body secretions such as saliva, tears, and sweat, as well as in the gastrointestinal, respiratory, and genitourinary tracts. Abbreviated IgA.  Each antibody binds to a specific antigen; an interaction similar to a lock and key. An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shape protein produced by plasma cells that is used by the immune system to identify and neutralize pathogens such as bacteria and viruses. The antibody recognizes a unique molecule of the harmful agent, called an antigen, via the variable region. Though strictly speaking, an antibody is not the same as an immunoglobulin; B cells can produce two types of immunoglobulins-surface immunoglobulins, which are B cell receptors; and secreted immunoglobulins, which are antibodies. So antibodies are one of two classes of immunoglobulins. Guide. An immunoglobulins test is done to measure the level of immunoglobulins, also known as antibodies, in your blood. Antibodies are substances made by the body's immune system in response to bacteria, viruses, fungus, animal dander, or cancer cells. 1 IgM antibodies are the largest antibody. 2  They are found in blood and lymph fluid and are the first type of antibody made in response to an infection. 3  They also cause other immune system cells to destroy foreign substances. 4  IgM antibodies are about 5% to 10% of all the antibodies in the body. Immunoglobulin: A protein produced by plasma cells and lymphocytes and characteristic of these types of cells. Immunoglobulins play an essential role in the body's immune system. They attach to foreign substances, such as bacteria, and assist in destroying them. Immunoglobulin is abbreviated Ig. The classes of immunoglobulins are termed immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin M (IgM), immunoglobulin D (IgD) and immunoglobulin E (IgE). Immunoglobulin. Definition. noun, plural: immunoglobulins. (1) Any of several classes of structurally related proteins in the blood serum, produced by plasma cells as an immune response against foreign agents (antigens). (2) The fraction of the blood serum containing antibodies. Supplement Wiktionary (0.00 / 0 votes) Rate this definition: immunoglobulin (Noun). Any of the glycoproteins in blood serum that respond to invasion by foreign antigens and that protect the host by removing pathogens; an antibody. 
http://medical-dictionary.thefreedictionary.com/immunoglobulin http://medical-dictionary.thefreedictionary.com/immunoglobulin http://www.merriam-webster.com/dictionary/IgG http://www.medicinenet.com/script/main/art.asp?articlekey=21066 https://en.wikipedia.org/wiki/Antibody http://www.webmd.com/a-to-z-guides/immunoglobulins http://www.medicinenet.com/script/main/art.asp?articlekey=12077 http://www.biology-online.org/dictionary/Immunoglobulin http://www.definitions.net/definition/Immunoglobulin
immunoglobulin definition