Immunoglobulins

Immunoglobulins are the antibody proteins of the adaptive immune system, secreted by B lymphocytes and plasma cells to identify and help eliminate pathogens and toxins ^[1]. Each molecule has a characteristic four-chain structure whose variable regions recognize a particular antigen and whose constant region links the antibody to the rest of the immune system ^[1]. Humans produce five classes, IgG, IgA, IgM, IgE, and IgD, which differ in size, location, and function; IgG predominates in the circulation and provides long-lasting protection, and it is the principal ingredient of therapeutic immunoglobulin preparations ^[1].

As a medicine, immunoglobulin therapy uses concentrated antibodies purified from the pooled blood plasma of thousands of healthy donors, giving each batch a broad repertoire of antibodies against many common viruses and bacteria ^[4]. The approach dates to the early 1950s, when weekly intramuscular injections were used to protect people who could not make their own antibodies ^[4]. Better-tolerated intravenous preparations became available in the 1980s, and by 2006 formulations designed specifically for subcutaneous self-administration at home had been introduced, giving patients more flexible options ^[4].

Immunoglobulin has two broad categories of use. As replacement therapy it prevents serious infections in people with primary or secondary antibody deficiencies ^[4]. At higher immunomodulatory levels it treats a range of autoimmune and inflammatory disorders, and a formal review of the evidence supports its use in conditions such as immune thrombocytopenia, Kawasaki disease, Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy, and certain other neuromuscular and dermatologic diseases ^[2]. In Guillain-Barre syndrome, for instance, intravenous immunoglobulin is an established treatment, though a portion of patients respond incompletely and outcome depends on clinical factors and the rise in serum antibody level achieved ^[3].

Therapeutic immunoglobulin is a plasma-derived biological product supplied for intravenous, subcutaneous, or intramuscular use, and it is listed by the World Health Organization as an essential medicine ^[2][4]. Most people tolerate it well, with transient reactions such as headache, flushing, fever, chills, and fatigue being the most common ^[2]. Less often, serious effects including kidney impairment, blood clots, aseptic meningitis, hemolytic anemia, and transfusion-related acute lung injury can occur, and slower infusion rates, premedication, or switching between intravenous and subcutaneous routes can reduce these risks ^[2].

Generally well tolerated, since they're food-derived proteins. Because most products are bovine-derived, people with dairy or milk-protein allergies should be cautious. Mild GI symptoms like bloating can occur early on. They're considered low-risk for most people.