Understanding MS – Causes of MSWhat does 'autoimmune disease' mean?? Why immune cells attack the body's own tie? How inflammatory foci develop in the brain? The next pages explain the crucial processes that lead to the development of multiple sclerosis.
A serious error in the maturation process
Multiple sclerosis is an autoimmune disease. It is based on incorrectly programmed T cells, which are the result of faulty maturation in the thymus:
– Normally, T cells in the thymus undergo several tests during maturation. – These maturation tests are intended to ensure that the T cells can distinguish between endogenous and exogenous substances. – For this purpose, the immune cells are confronted with the body's own substances. – T-cells that react to these are destroyed so that they cannot attack the body's own healthy cells. – Due to an error in the selection process, a T cell is overlooked that has reacted to the body's own structures. – The misprogrammed autoimmune T cell survives, multiplies, and is released into the circulation with its daughter cells.
The overcoming of the blood-brain barrier
Normal resting T cells are usually unable to cross the blood-brain barrier.
However, a wrongly programmed, autoimmune active T-cell succeeds in the transition. How this happens has not yet been conclusively researched.
© DMSG Federal Association V.l.n.r.A serious error in the maturation process, The overcoming of the blood-brain barrier, The destruction of the body's own tie.
The destruction of the body's own tie
Once the incorrectly programmed T cells have reached the brain, they begin to attack the body's own cells:
– Their target is the oligodendrocytes, which form the myelin sheaths of the nerve fibers. – T cells emit cytokines to attract other comrades-in-arms such as phagocytes, antibodies and complement system. – An inflammatory reaction occurs, which attacks the myelin sheaths. – At the same time, the T cells divide and their daughter cells attack more myelin sheaths: more and more foci of inflammation develop. – In addition, B cells may also be involved in this destruction via release of myelin-specific antibodies. – The insulation of the nerve fibers is destroyed by the attacked myelin sheaths. – The result: nerve impulses are transmitted more slowly or not at all.
How do nerve cells exchange information? What have an electric cable. A nerve fiber together? How the CNS monitors border traffic? Learn below how a nerve impulse is generated and what the insulating layer of neurons is all about.
Control center of the body
The human nervous system processes information from the environment and from its own body. It ensures that humans can think, feel and act and that their organs function in a complex interaction.
At the center of this network is the brain, which is made up of up to 100 billion nerve cells, or 'neurons'. Together with the spinal cord, it forms the central nervous system (CNS).
Information exchange through electricity
– Consist of a cell body, a filamentous projection (axon), and several highly branched outgrowths (dendrites). – Use electricity for information flow: when the excitation of the cell body exceeds a certain threshold, electrical voltage builds up – the 'action potential'. – Conduct this energy in a flash via the axon. – Have special contact points to other nerve cells: the synapses. – Receive information from other nerve cells via these synapses.
Myelin as insulation
V.l.n.r.: Control center of the nervous system, information exchange by electricity, myelin as insulation.
An insulating layer that surrounds the axon of the nerve cell like that of an electric cable ensures that the electrical impulse is transmitted quickly and smoothly: the myelin sheath.
– This myelin sheath is formed by a specific type of cell in the CNS called 'oligodendrocytes'. – The individual myelin sheaths line up on the axon like pearls on a string – They are separated by 'Ranvier's lacing rings' – The nerve impulses can jump from one lacing ring to the next thanks to the insulating myelin.
A nerve fiber sheathed in myelin can transmit a nerve impulse about ten times faster than one that lacks the myelin sheath.
Protection from the outside
Brain and spinal cord are very sensitive.
Next to skull bones and bony spinal canal, they are protected by a fluid-filled cushion. This fluid – also called neural fluid or 'cerebrospinal fluid' – is in direct communication with the tie fluid of the brain.
The central nervous system uses a special barrier to prevent harmful substances from entering the brain from the bloodstream.
Protection from the inside
The blood-brain barrier
– Consists of the walls of the blood vessels, which are reinforced here – Is formed by endothelial and supporting cells that form particularly strong connections – Prevents pathogens and immune cells floating in the blood from gaining access to the brain and spinal cord, thus monitoring border traffic.
Inflammatory cells normally cannot penetrate this barrier – unless they put on a cloak of invisibility and crack the code needed to pass through it.
How our organism defends itself against invaders? Can immune cells communicate with each other? Why our body must also protect itself from itself? On the following pages, you can learn more about how the immune system works and what self-tolerance is all about.
The body's immune system protects humans from pathogens such as bacteria, viruses and fungi. A distinction is made between general and specific immune defenses.
General or nonspecific immune defenses include:
– the leukocytes, a subgroup of the white blood cells – the macrophages and – the complement system
The main role of the specific immune defense is played by a subgroup of white blood cells – the lymphocytes. These include:
– the T-cells and – the B-cells.
Mediators between these different types of cells that are important for the immune response are cytokines. Finally, the body must protect itself from possible attack by its own immune defense system: here is 'self-tolerance'. of great importance.
The general or non-specific immune defense
– This includes the complement system, which consists of various proteins that constantly patrol the bloodstream. – It recognizes invaders such as z.B. bacteria and tries to eliminate them by breaking down their cell walls. – The complement system is supported in this by phagocytic cells. – Phagocytes take up the bacterium and digest it. – Digested remnants of the bacterium are then presented as antigens on the surface of the phagocytic cell. – This 'antigen presentation' turns on specific immune defenses. – To do this, the phagocyte migrates to the nearest lymph node.
Specific immune defense: the T cells
T cells are a subgroup of white blood cells. – They have special docking sites or 'receptors' that only match very specific antigens – like a key in a lock. – In the lymph node, T cells attempt to dock with the antigen-presenting phagocyte. – If the antigen matches the receptor, the T cell multiplies. – Their daughter cells leave the lymph node in search of the pathogens whose antigens have been presented by the phagocyte.
Specific immune defense: the B cells
B cells also belong to a subset of white blood cells. – Their central function is the production of antibodies. – On the surface of the B-cells there are antibodies as receptors that only match a very specific antigen. – Binds z.B. a matching bacterial antigen to the receptor, the B cell thus activated divides and produces specific antibodies. – These antibodies then dock onto the bacteria. – This in turn attracts phagocytes that participate in eliminating the invaders.
Cytokines – the silent mail of the immune system
– Cytokines are messenger substances with the help of which the cells of the immune system communicate with each other. – They are produced by very different immune cells. – For example, if a T cell reaches the bacteria it is primed to target, it attaches to it. – Next, the T cell requests further support from B cells by secreting cytokines.
Through the interaction of all parts of the immune system, the foreign invaders are successfully repelled and destroyed.
Normally, a built-in self-protection ensures that immune cells do not target the body's own healthy cells. This imprinting occurs in the thymus, an organ of the lymphatic system located above the heart. This is where the selection process of T cells takes place:
– T cells are produced as immature cells in the bone marrow. – In the thymus they mature into differentiated T-cells. – For this purpose, T cells are confronted with the body's own substances to which they attempt to dock. – If this is unsuccessful, the T cells are found to be mature and correctly programmed: they may be released back into circulation. – If a T cell finds a suitable antigen, it is eliminated. – This 'self-tolerance' ensures that only those T cells that are not directed against the body's own structures survive and are multiplied.
How MS sufferers often notice it for the first time? Can you hear MS? What does a tingling sensation in the foot have to do with MS?? Answers to these and more questions about the symptoms of multiple sclerosis can be found in the following chapter.
Multiple sclerosis often attacks the optic nerves. About one million nerve fibers are bundled in them. If the myelin layer is damaged or destroyed here, this can lead to various symptoms:
MS often affects the cerebellum. It coordinates movement sequences and ensures that muscles are tensed and relaxed again. The cerebellum receives and processes an enormous amount of information via its approximately 200 million nerve fibers and is responsible for a correspondingly large number of different functions. These include
The staggering gait in MS is sometimes misinterpreted as drunkenness – but in reality it is gait ataxia.
Muscle weakness and paralysis
Another common MS symptom is muscle weakness, for example in the arms or legs. Commands from the CNS no longer reach the muscles, or only to a reduced extent. Loss of muscle strength can lead to paralysis. Require walking aids as the disease progresses. Often the affected muscles are stiff and cramped (spastic), which may also be associated with pain.
The brain not only sends commands to organs and muscles, it is also responsible for receiving signals from the environment.
Multiple sclerosis can interfere with the reception and transmission of stimuli such as pain, cold and heat. Feet that feel numb or tingle are one of these sensory disturbances.
People with MS often suffer from severe fatigue, which is typical of the disease.
Urinary urgency and loss of libido
The function of the bladder is also often affected in multiple sclerosis. As the disease progresses, sufferers may feel the need to constantly visit the toilet.
In the course of the disease there are also frequent disturbances of the sexual function such as impotence or a reduced feeling of pleasure.
How nerve fluid is obtained? Can MS foci be detected with magnetic fields? How does a checkerboard help with diagnosis? In this chapter, you will learn the most important examination methods to confirm the diagnosis of 'MS'.
There is no single test that alone can detect multiple sclerosis. The diagnosis results from the results of several examinations.
– Neurological examination – evoked potentials (EP) – magnetic resonance imaging – (MRI) lumbar puncture
Muscle strength and reflexes
One of the basic investigative procedures for MS is the neurological examination. The physician examines the patient:
– Muscle strength – fine motor skills – coordination – sensitivity – muscle tension – reflexes
This basic neurological diagnostic test, which is easy to perform, together with information from the patient, can already provide valuable clues to the presence of MS.
Stimulus and reaction
The determination of the so-called 'evoked potentials' belongs to the more special examination methods.
Individual sensory organs are stimulated – for example, the eyes by the optical stimulus of a (changing) checkerboard pattern. Nerve pathways transmit this stimulus as electrical impulses. These 'visual evoked potentials' measure how long it takes for the brain to respond to the offered stimulus.
Slowed conduction velocity may be due to inflammation of the optic nerve and is indicative of MS. Magnetic resonance imaging (MRI) is a diagnostic imaging technique. Does not require the use of X-rays. Cross-sectional images of the body are made using an artificially generated magnetic field.
Small inflammations and scarring in the brain are clearly visible on them. MRI can also detect active foci of inflammation during a relapse. These foci often disappear again after the spasm has subsided.