Globulin, Serum

The main two types of protein in your blood are albumin, the main carrier protein, and globulin, the main immune protein. Low levels of globular protein can weaken your immunity, while higher levels can indicate increased inflammation in the body.

Globulins are produced by the liver and the immune system. Albumin makes up more than half of the total protein within the blood, and globulins make up the remainder. Globulins have multiple different functions; the group includes immunoglobulins, enzymes, carrier proteins and complement.

There are four groups of globulins. Serum protein electrophoresis is the test used to distinguish one from another and establish levels of each within the bloodstream.

Alpha 1 globulins

• Mainly alpha-1 antitrypsin.

Alpha 2 globulins

• Alpha 2 macroglobulin.
• Haptoglobin.

Beta globulins

• Transferrin.
• Complement components C3, C4, C5.

Gamma globulins

Mostly immunoglobulins (antibodies):

• IgG: majority of the immunoglobulin component. Many antibodies to bacteria and viruses are IgG.
• IgE: involved in allergic response. Triggers histamine release. Also protects against parasites.
• IgM: largest antibodies and first type produced in response to infection.
• IgD: exists in very small quantities in blood. Function not very well understood.
• IgA: found in mucous membranes, blood, saliva and tears. Protect body surfaces which are exposed to foreign substances.

Source:

• Loh RK, Vale S, McLean-Tooke A; Quantitative serum immunoglobulin tests. Aust Fam Physician. 2013 Apr42(4):195-8.

• Bird JM; Investigating an incidental finding of a paraprotein. BMJ. 2012 May 4344:e3033. doi: 10.1136/bmj.e3033.

• Immunoglobulin; Public Health England

• Busher JT; Serum Albumin and Globulin

• Serum globulin electrophoresis; MedlinePlus

• Monoclonal gammopathy of undetermined significance (MGUS); Melbourne Haematology

• Immunoelectrophoresis - blood; MedlinePlus