Gamma globulin is a class of protein found in blood plasma. There are different types of gamma globulins, but the most important are immunoglobulins - also called antibodies - which help to both prevent and fight infections and disease. Abnormal amounts of proteins in this class can be bad for a person's health or can indicate a disease. In medicine, immunoglobulin injections made from donated human blood are used to treat certain conditions, especially those that weaken the immune system