Immunoglobulins are proteins produced by plasma cells, a type of white blood cells and are an important part of your defense system. There are 5 types of immunoglobulins namely IgG, IgM, IgA, IgE & IgD. Immunoglobulin M constitutes 5% of the total immunoglobulins. It is the first antibody to be secreted in response to a foreign antigen entering your body. IgM provides short term protection while your body makes other antibodies like IgG. Patients with Hyper IgM syndrome have very high levels of IgM in the blood and are prone to severe infections & increased risk of cancer.