Gamma globulins (y-globulins) or antibodies are the most abundant class of serum proteins after albumin. The main classes of gamma globulins are IgA, IgG and IgM. The electrophoresis interpretation indicates one of two types of increases in gamma globulins: an increase in all subtypes (polyclonal hypergammaglobulinemia) or an increase in one class of antibodies (monoclonal hypergammaglobulinemia).
A polyclonal increase in gamma globulins represents a normal defensive reaction by the body and can therefore be observed in infections such as viral hepatitis, chronic inflammatory diseases, autoimmune diseases, cirrhosis, etc.
A monoclonal increase (one class) of gamma globulins generally reflects the overproduction of a particular class of antibodies by the bone marrow as in multiple myeloma and is sometimes of limited clinical interpretation as in the MGUS (“monoclonal gammopathy of undetermined significance”).
Low levels of gamma globulins suggest the under-production of antibodies as found in certain genetic diseases (bubble boy agammaglobulinemia) and leukemia.
Other tests can more accurately identify which fraction or sub-component of gamma globulins may be abnormal (protein immunofixation, free kappa or lambda chains).