Abstract
The term ‘immunoglobulin’ describes the structure and function of a class of proteins present in the body, and particularly in the blood: they are globular proteins which have a role in providing immunity, and are also known as ‘antibodies'. Immunoglobulins can be classified both according to their content and to their mode of administration. Standard pooled immunoglobulin is derived from the plasma of unselected normal donors. It may be given intravenously (IV), in which case it is known as IVIG (Ig being an abbreviation for immunoglobulin), or by the subcutaneous (SC) or intramuscular (IM) route: SCIg or IMIg. Hyperimmune immunoglobulins contain a high level of antibodies against specific pathogens.
Donors have to be selected for, or inoculated to produce, high levels of reactivity. Their plasma is used to manufacture specific immunoglobulins to prevent or treat diseases such as hepatitis B, tetanus or haemolytic disease of the newborn in which rhesus incompatibility between the mother and her foetus can lead to the death of the baby. This article focuses on standard pooled preparations. The body responds to infections with a succession of steps. Firstly the large, broad acting IgM antibody is produced. Meanwhile white blood cells start producing the smaller, more specific IgG molecule in high quantities. It is this type of antibody which is the most prevalent in the blood, accounting for 70–75% of the total immunoglobulin pool. The other classes of antibodies are IgA, IgE and IgD. Antibodies are Y-shaped proteins that bind to antigens with both upper arms of the Y. Under normal conditions an antibody binds to an antigen (a bacterium, virus, or other pathogen) and “tags” it for destruction.
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