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What are Antibodies?

This article was written by Karen Robinson, formerly a Registered Osteopath. 

I shared a video a few days ago on our Facebook page which explained a little more about the immune system and how it works. (You can watch the video here.) There were some names and terms that were used and I thought I would explain more about them here.  They were talking about IgG and IgM.

In a previous blog (“What is your immune system?”) I introduced white blood cells which are called leukocytes. There are 2 types of leukocytes: Phagocytes and Lymphocytes. Plus, there are 2 types of Lymphocytes: B-Lymphocytes and T-lymphocytes.

Once B-Lymphocytes spot the antigen (any substance that can spark an immune response – bacteria, fungus, virus, toxin, drugs) they begin to secrete antibodies, (antigen is short for “antibody generators”).

Antibodies are special proteins that lock on to specific antigens. Each B cell makes one specific antibody. For instance, one might make an antibody against the bacteria that cause pneumonia, another different one for chickenpox and so on.

Antibodies are part of a large family of chemicals called immunoglobulins, which play many roles in the immune response, and they can be measured by doing a blood test.

The five types of antibodies:

  • Immunoglobulin G (IgG) — Is the most common immunoglobulin and marks microbes so other cells can recognise and deal with them. This is the most common antibody. It’s in blood and other body fluids, and protects against bacterial and viral infections. IgG can take time to form after an infection or immunisation.
  • IgM — is expert at killing bacteria. Found mainly in blood and lymph fluid, this is the first antibody the body makes when it fights a new infection
  • IgA — Is the second most common immunoglobulin and is found in the linings of the repertory tract and digestive system, as well as in saliva (spit), tears, and breast milk where it protects gateways into the body.
  • IgE — normally found in small amounts in the blood. There may be higher amounts when the body overreacts to allergens or is fighting an infection from a parasite – think asthma or allergic reaction to something.
  • IgD — stays bound to B lymphocytes, helping them to start the immune response.

Antibodies lock onto the antigen, but they do not kill it, only mark it for death. Think about a crowd of people – how do you recognise the invader? Think about the antibody being a tall coloured hat, easily seen and recognised.  The killing is the job of other cells, such as phagocytes.