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The Immune System and Multiple Sclerosis


What does the immune system have to do with MS?

There is strong evidence that multiple sclerosis is an autoimmune disease. Autoimmune diseases are disorders of the immune system where the cells that are responsible for identifying and destroying harmful invaders mistakenly identify elements of the body's own tissue as foreign and attack it. However the case is not yet proven and some serious researchers offer alternative explanations - most notably viral or bacterial causes such as Human Herpes Virus 6, Epstein-Barr virus and Chlamydia Pneumonia bacterium.

However the issue is finally resolved, there can be little doubt that the immune system is responsible for much of the damage seen in multiple sclerosis. Recently, much of the MS research effort has concentrated on how the immune system behaves in people with the disease and, in this section, I want to describe our current understanding of the immunology of multiple sclerosis.

Tell me a bit about the immune system

The human body contains about 60 trillion cells. Seen from the point of view of microbes (bacteria, viruses, fungii and the like) this is a vast environment where a good living can be made. Most of these microbes do us little or no harm and some are even beneficial, helping us digest our food. However some, called pathogens, cause disease and can kill us if left to their own devices.

The immune system is the body's defence to pathogens. It's our internal army and it's job is to identify and kill invaders. It's an amazingly elaborate network of white blood cells (leukocytes), rivalled only by the central nervous system for complexity. Fifty years ago little was known about how the immune system worked but the recent massive explosion in cellular biology has shed some light on how it works although much of it is still dimly understood.

Traditionally, the immune system is divided into two parts - the innate or natural immune system and the acquired or specific immune system. In fact, this division is far from complete and the two systems communicate and rely upon eachother extensively. Cells from both are involved in the destruction caused by MS.

The innate immune system

The innate immune system is like the booby-traps laid in the ancient Egyptian tombs to deter grave-robbers. It consists of:

We are born with our innate immune system and it is ready for action even before we are born. The cells of the innate immune system are of two types: By and large, the innate immune system is unable to recognise specific invaders. It's all-purpose defence mechanism but is vulnerable to pathogens that have evolved ways to avoid its many traps. This is what other division of the immune system, the acquired immune system, is evolved to deal with.

The acquired immune system

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