Immunoglobulins are preparations that contain antibodies against one or multiple infections. Thus they confer passive immunity.
What is the difference between antisera and immunoglobulins?
Immunoglobulin preparations are obtained from human individuals with immunity against the specific disease. Likewise, antisera are similar antibody-based preparations but obtained from animal sources.
Hypersensitivity reactions are more common in patients given anti-sera than immunoglobulins.
Immunoglobulins and antisera do not confer lifelong immunity. They are effective only for some weeks after which a repeat dose may be necessary.
What are the different types of immunoglobulins?
Immunoglobulins are actually antibodies produced by the plasma cells (activated B cells) in response to antigens.
Antigens may be allergens, infective agents or self-antigens (as in the case of autoantibodies).
Antibodies/ Immunoglobulins are further subdivided into five different classes:
- IgA or immunoglobulin A
- IgG or immunoglobulin G
- IgM or immunoglobulin M
- IgD or immunoglobulin D
- IgE or immunoglobulin E
What is IgA antibody or immunoglobulin A?
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IgA antibodies are usually found in the mucosal and secretory areas of the body such as the nose, breathing passages, digestive tract, ears, and eyes.
These antibodies protect the body surfaces that are exposed to outside foreign substances. IgA antibodies are found in tears, saliva and gastrointestinal secretions of the body.
IgA antibodies make 10-15% of the total antibodies
What is IgG antibody or immunoglobulin G?
IgG antibodies are produced in response to antigens and circulate in the body fluids and blood. IgG antibodies, when present, are indicative of past exposure to the same antigen and confer long-term immunity.
These are among the smallest of the antibodies and thus can cross the placenta. Up to 75% of all the antibodies in the human body are the IgG type.
What is IgM antibody or Immunoglobulin M?
IgM is usually the first of the immunoglobulins to strike a foreign antigen or infections.
Their levels then slowly decline when IgG levels start rising. IgM, when present in the blood, are suggestive of a recent infection.
These molecules are the heaviest of all and comprise 5 to 10 % of the total immunoglobulins.
IgD and Ig E antibodies:
IgD is not fully understood and has been recently discovered to participate in activating basophils and mast cells.
Thus they may be part of the immune system of the respiratory system.
Ig E antibody is a marker of allergy to foreign antigens like pollens, furs, and parasites, etc. These are specially raised in patients with allergies like allergic asthma.
These immunoglobulins are also raised in patients with parasitic and fungal infections.
How are immunoglobulins prepared and administered?
Immunoglobulins for commercial use can be subdivided into those which are disease-specific and the normal immunoglobulins (N-Ig).
Human N-Ig is obtained from at least a thousand donors. It contains antibodies of the IgG type and is effective against hepatitis A, measles, mumps, rubella and varicella. It is given by intramuscular injections and contains 10-18% of proteins.
Before starting treatment with IVIG, patients should be tested for Hepatitis B surface antigens, antibodies against hepatitis C and HIV infections.
The intravenous formulation is given in deficiency states like agammaglobulinemia, hypogammaglobulinemia, immune thrombocytopenic purpura, and Kawasaki disease.
It is also given as a prophylactic treatment for the prevention of infections in patients with bone marrow transplantation and in HIV patients with recurrent bacterial and viral infections [varicella immunoglobulin]. The intravenous formulation is also preferred in patients with Guillain Barre syndrome.
