The primary antibody against infection, in the circulation, is mainly IgG, but there is also IgM in the circulation as well as IgD and IgE, which are likely to be able to play a role as well. Like IgD, there are no particularly clear hints about its main role, so its role is still unknown. In most cases, however, it is thought that what is known to have an anti-infective effect in the circulation is IgG. Antibodies to these IgG are extracted from blood products and have the effect of preventing further aggravation of the infection, and these immunoglobulins can be applied in many cases of serious infections. In addition, if a particular pathogen is involved, the protective antibody is also IgG.