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
2
: an antibody of the class IgG
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Merriam-Webster unabridged
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Time Traveler for IgG
The first known use of IgG was in 1965
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