Today we are going to discuss the second line of defence of your immune system; the adaptive immune system.

The Adaptive Immune System.

It involves specific responses of your immune system in regard to different pathogens.  There are two properties that distinguish the adaptive immune system from the innate immune system form each other:

• The ability to distinguish between cells of the body and cells of invaders.
• The ability to memorize previously encountered invaders.

The adaptive immune system responds in two different ways:

• Antibody-mediated immunity.
• Cell mediated immunity.

Antibody Mediated Immunity.

This involves the Beta-cells or Beta-lymphocytes (white blood cells) that are formed in the bone marrow hence B-cells.  B-cells are armed guards that do combat and also hold a grudge against past offenders. Your body has the ability to produce millions of these B-cells on a daily basis.

Each B-cell has a unique receptor on its membrane that enables it to bind to only one particular pathogenic antigen. An antigen is a marker on the surface of cells that acts as an identification feature, like fingerprints. This enables the immune system to identify foreign cells and to destroy them. (picture fingerprints)

When a B-cell encounters a pathogenic cell with which it can bind, it secretes antibodies to that specific antigen.  These antibodies combine with all the pathogens of the same type, like a lock in a key (picture key in a lock) and form an inactive complex that makes it an easy target for phagocytes to recognize and destroy. The anti-bodies also signal other immune cells to join the battle.

During the initial stage some of the B-cells differentiate into memory cells that ensure a rapid and aggressive response whenever the same antigens are encountered in your body.

 

Cell-mediated Immunity.

These immune cells are formed in your thymus (a walnut size gland under the breastbone) hence the name T-cells. There are two types: Killer T-cells and Helper T-cells.

Killer T-cells. These cells are the army troops that patrol the bloodstream and lymphatic system for intruders or antigens and engage in hand-to-hand combat with the threat. The T-cells release Perforin that punctures the membrane of the anti-body, compromise the cell content and kill them on the spot.

Killer T-cells are responsible for the destruction of cancer cells.  Cancer cells have altered cell membranes that distinguish them from healthy cells and the killer T-cells recognize these foreign cells and destroy them. Growths are formed when cancer cells multiply at a faster rate as what they can be destroyed by the killer T-cells.

Helper T-cells. As the name suggests helper T-cells support the action of anti-body mediated immunity. Helper T-cells also release proteins which stimulates B-cells to produce antibodies.

 

Cell Products and Messenger Molecules.

A vast array of biological products is manufactures by the immune system. These chemicals are responsible for the communication between the immune cells, changing the behaviour of immune cells and co-ordinating immune response.

 

Food for Thought.

Recent discoveries have proved that certain neurotransmitters and neuropeptides which carry messages through the nervous system also carry messages to the immune cells. Receptors for brain chemicals have been found on Natural Killer cells.

 In the same way immune messenger molecules e.g. interleukin-1 communicates effectively with the brain.  It seems these two systems speak the same language.