The article reviews the evidence supporting and explaining suppressive activity of intravenous immunoglobulin (IVIG) preparations towards human immune system. Besides basic mechanisms also clinical applications and effects in various autoimmune disorders such as idiopathic thrombocytopenia, Guillain-Barre syndrom and others are described. This evidence supports novel application of IVIG as convenient alternative to other immunosuppressive therapies with many more adverse effects.