IgM is a class of immunoglobulin, which is the first line of defense against infection. It is the most abundant antibody in human blood and can be found in all body fluids. IgM is produced by plasma cells and B cells in response to antigens. It plays an important role in clearing bacteria and viruses from the body.
IgM is a pentameric protein with a molecular weight of about 950 kDa. It consists of two heavy chains and two light chains, which are connected by disulfide bridges. The Fc region of IgM contains four subunits: twoalpha subunits, beta subunit, and gamma subunit. The variable regions of the heavy chains are responsible for binding to antigens. The structure of IgM allows it to bind to multiple antigens at once through its Fab region. This gives IgM the ability to neutralize pathogens quickly and efficiently.
IgM is produced early during an infection and can be found in high concentrations in the blood within days of exposure to an antigen. It has a short half-life and is quickly replaced by other antibodies such as IgG when the infection has resolved. However, some pathogens are able to evade detection by the immune system and establish themselves as chronic infections. In these cases, IgM may be present for long periods of time as it continues to bind to new antigens that are produced by the pathogen .
IgM is an important part of the humoral immune response and helps protect against bacterial and viral infections . It can also be used diagnostically to detect certain infections, such as Epstein-Barr virus (EBV) or cytomegalovirus (CMV). Additionally, levels of IgM may be elevated in autoimmune diseases such as lupus erythematosus or rheumatoid arthritis .