The significance of IgM and IgG antibody detection
When the human body contacts with foreign antigens, the first antibody produced is IgM, which is secreted directly by the receptor on the surface of B cells. The B cells that produce IgM enter the lymph nodes, receive stimulation from T cells and antigen-presenting cells in the center of occurrence, further mature, differentiate into plasma cells, and produce large amount of IgG.
IgM is usually produced 3-7 days after infection. Therefore, IgM can be used to reflect whether the body is in an acute infection state, as the main indicator of early diagnosis.
IgG appears later than IgM when infected with 2019-nCoV, but it can persist in the blood for several months, so positive IgG may indicate patients were ever infected with virus.