Antibodies can act like adjuvants. They can potently enhance the antibody response, and in
the case of IgG and IgE also the T cell response, to the very antigen they are specific for. In
this review we will discuss the recent advances made in our understanding of the underlying
mechanisms of antibody-mediated feedback enhancement. The immuno-stimulatory
properties of IgM, IgG1, IgG2a, IgG2b, IgG3 and IgE will be reviewed in relationship to the
complement system and Fc receptors and the physiological relevance will be discussed.