Autoimmune Disease: What is Multiple Sclerosis? Lewis Jordan

Autoimmune Disease: What is Multiple Sclerosis?

Lewis Jordan Lower Sixth

Healthy nerve cell (left) vs nerve cell damaged by MS (right)

With Covid having considerably raised its profile in recent years, the immune system is the highly complex collection of organs, tissues, cells and proteins involved in providing the body’s defence against pathogens (disease-causing microorganisms).

White blood cells are key parts of immunity and, having been generated within our bone marrow, they move throughout the body via tissues and the bloodstream. They look to identify foreign invaders to the body and, once discovered, initiate an immune response. Under normal circumstances this response will seek to stop an infection by killing pathogens and therefore preventing their spread. However, in certain cases, this response does not happen in the prescribed way.

Antigens are an important type of molecule within the immune system. They are present on the cell surface of both human cells and pathogens; however, the shape differs. There are two types of antigens; self- and non-self. Self-antigens originate from within the body whereas non-selfantigens are identified as foreign and upon discovery should therefore provoke an immune response. The body’s methods of differentiation between the two are vital in determining how diseases are prevented from manifesting. immune system attacks the Central Nervous System (CNS). It is a lifelong and life-limiting condition and, although it is possible to treat the symptoms, it is an incurable disease. The condition itself is usually divided into two main branches: Relapsing-Remitting MS (RRMS) and Primary-Progressive MS (PPMS).

If the body becomes confused, believing [N]early three The CNS is made up of the brain and spinal that self-antigens are foreign (non-self), our antibodies and million people living with cord and is responsible for the coordination of sensory information. autoreactive immune the condition Comprised of two cells begin to attack normal body cells worldwide. types of cells, nerve cells (neurons) and leading to what is support cells (glia), known as autoimmunity. Unfortunately, the CNS ensures the correct transportation this counterproductive immune response throughout the body of messages results in diseases referred to as (electrical impulses). “autoimmune diseases” of which there are 80 or so. Although the causes of MS are not definitive, an abnormal immune response One such autoimmune disease is Multiple leading to CNS damage has been linked Sclerosis (MS), a condition where the to MS development. In an MS patient, a host of white blood cells enter the CNS attacking the self-antigen cells, believing them to be dangerous. Here, they release cytokines (a type of protein) which triggers an inflammatory response. In addition, the malfunction of other immune cells failing to turn off this response leads to the damage seen in MS. These damaged areas of activity are known as lesions or plaques and can be seen on MRI scans of the brain and spine, a key factor in aiding diagnosis.

an extension connecting one nerve to the next. The axon is sheltered by the insulating myelin sheaths, which protects the travelling electrical impulses from interference. Glial cells then surround and support the nerve cells with their oligodendrocytes producing myelin to regenerate the nerve cell protection.

When focusing on what causes MS, there are slight differences between relapses and just gradual progression. Due to remyelination (partial restoration of damaged myelin), remissions, as well as relapses, can be seen over time in RRMS. However, in PPMS remissions do not develop because the oligodendrocytes are unable to repair the damaged myelin, which means that the easing of symptoms is not seen. Eventually scarred areas of myelin leave exposed nerve areas, therefore interrupting the vital communication network and generating the symptoms categorical of MS.

A host of other causes have been theorised including areas of epidemiology, genetics and infectious agents. Geographical gradient has been identified as a risk factor in that MS is known to occur more frequently in areas further from the equator. There is also growing evidence to suggest that low vitamin D levels in the blood can be a risk factor for MS development.

In terms of genetics, MS is not considered an inherited disease. However, from the frequency in the general population of 1 in 800, there is a significant rise to a 1 in 4 chance in the case of identical twins.

One notable avenue of investigation is the link between MS development and the contraction of the Epstein-Barr virus (EBV). This virus is mostly found amongst teenagers and young adults, causing a range of symptoms including extreme fatigue, fever, and headaches.

Early symptoms of MS, signalling gradual demyelination (destruction of myelin), can begin long before the condition is officially diagnosed. These include an abnormal feeling or pain in the arms, legs, trunk or face, loss of strength or dexterity in a leg or hand and problems with vision.

Between the two main branches, PPMS tends to affect the day-to-day functioning of the body more so than RRMS. With further progression, both branches display more of the same symptoms, including vision problems, muscle weakness, balance issues, numbness and prickling feelings in hands, legs and other areas, difficulties thinking clearly and evident fatigue.

When diagnosing the different types of MS, there is a disparity in the identifying criteria. For PPMS, due to its fairly gradual progression, it takes, on average, two to three years longer to diagnose than RRMS.

For a confirmed diagnosis of PPMS, there must be one year of disease progression (worsening without remission) and two from the following: a typical MS lesion on the brain; two or more similar lesions in the spinal cord; and evidence of immune system activity in the CNS found in spinal fluid.

However, with RRMS, there only has to be evidence of two separate areas of damage in the CNS from different points in time, combined with a symptom history, neurological examination and elimination of other possibilities. Due to the fact that there is currently no cure for MS, the only form of treatment is targeting the wide range of symptom presentations as no single treatment is universally effective. Corticosteroids (a type of steroids) are commonly used for acute attacks, suppressing the immune system and providing short-term relief of immediate symptoms. These are not, however, used in the long term due to the wide variety of side effects experienced such as thinned skin that bruises easily, increased risk of infections and high blood pressure.

Current experimental treatments are now targeting the behaviour of immune cells to prevent attacks on myelin. This has been proven to be most effective for relapsing MS where immune attacks are the common cause of symptoms. The prescribing of Ocrelizumab is a separate treatment that targets white blood cells and prevents them from attacking myelin. This was only recently approved for prescription on the NHS in May 2019. Generally, in terms of treatment the more the MS progresses, the less effective treatments prove at symptom alleviation.

Around 85% of all diagnosed MS patients have the relapsing form, whereas only 10% have the progressive form. There are also distinct differences in the age of onset; with PPMS diagnosis typically occurring in those in their 40s and 50s, compared to those in their 20s and 30s diagnosed with RRMS. In terms of prognosis, MS reduces life expectancy on average by 7 to 14 years. Between the two main branches, patients with progressive MS have a higher mortality rate than those with the relapsing form. Those that suffer from the relapsing form of the condition may go on to develop a progressive type of the condition, known as Secondary Progressive MS (SPMS).

Although not considered a fatal disease, MS is still chronic and incurable with nearly three million people living with the condition worldwide every day.