White Blood Cells: Your Body's Free Virus Removal System

Your body is under constant attack from viruses and most of the time you'll know nothing about it, thanks to the first class efforts of your very own virus removal program. The body also seeks out and destroys bacteria, but this article is primarily a simple guide about the removal of viruses.

The work starts in the bone marrow, which is the factory for making white blood cells, the critical components of your anti-viral programme. Two types of white blood cells are involved in the immune response - B and T cells.

Viruses don't make it easy for white blood cells, they are constantly evolving and changing the receptors on their protein coats. It's these receptors that white blood cells recognise as alien. They are like targets that the immune system homes in on to begin the removal of the virus threat.

B cells produce antibodies, these are proteins that stick to the virus that they've been designed to recognise. They recognise a specific part of the virus molecule, known as an antigen (antibody generator).

Antibodies are capable of extraordinary variability due to rearrangements of their DNA. Only a small number of changes are needed to come up with a vast array of combinations of amino acids, which are the building blocks of proteins. It's this diversity that means the body can cope with the great number of different viruses out there. Typically, billions of different types of antibodies can be created, although they won't all be in use at any one time.

To understand the source of the variability, we need to consider the structure of the antibody protein molecule. First of all, there are five classes of antibodies - IgG, IgM, IgA, IgD and IgE. Ig stands for immunoglobulin. Each one is a 'Y'- shaped molecule - consisting of four polypeptide chains; two heavy chains and two light chains. The source of the sheer variety of antibody molecules are the highly variable light and heavy chain sections in the left and right arms of the 'Y' shape. It's these parts of the antibody that stick to the target virus or the cell that has been attacked. The virus is removed either by the virus itself or by other white cells that recognise that an antibody has targeted a virus-infected cell for elimination. The trunk of the 'Y' is the constant end and it is attached to a B cell.

Other key players in the immune response are the two types of T cells; Helper T cells and Killer T cells. Helper T cells are involved in the production of antibodies and they also help the killer cells develop. Killer T cells, as the name suggests are tiny assassins that destroy the cells that have been invaded by viruses. This stops viral replication in its tracks.