Which functions are associated with IgM?

IgM, or Immunoglobulin M, is primarily known for its role in the immune response, particularly during the initial phases of infection. One of its most significant functions is the activation of the complement system. When IgM binds to a pathogen, it undergoes a conformational change that allows it to efficiently activate the classical complement pathway. This activation leads to a cascade of reactions that facilitates the opsonization of pathogens, enhances phagocytosis, and promotes inflammation, ultimately leading to the destruction of the identified pathogens.

While IgM does indeed perform other functions such as binding to microorganisms and neutralizing pathogens, its capacity to activate complements is a defining characteristic that highlights its crucial role in the immune response. In contrast, the role of providing immunity to newborns primarily falls to IgG, which can cross the placenta, while the neutralization of bacteria and viruses is a broader function usually attributed to various immunoglobulin classes including IgG and IgA.