Antibodies. Proteins produced by the individual’s immune system in direct response to specific structures (antigens) that are recognized as foreign and/or dangerous substances.

Antigen. Any substance, either within the body itself or outside of it, that is capable of inducing the production of antibodies.

Antigen-presenting cells. Cells that contain in their membrane HLA molecules and peptide (self, such as myelin, or foreign, such as viruses or bacteria) are called antigen-presenting cells.

Ataxia. Impairment of motor coordination due to a lack of conscious, deep sensitivity (spinal ataxia) or impairment of the cerebellar system (cerebellar ataxia).

Autoimmune disease. A disease in which there is a deprogramming of the immune system, which attacks not only dangerous foreign substances (such as bacteria, viruses, etc.) but also the body itself.

Brain barrier. Barrier between the blood vessels and the tissues of the brain, the purpose of which is to restrict or filter substances that can pass from the blood to the brain. This barrier protects the brain from the effects of many hazardous substances, but also hampers the administration of drugs to the brain.

Cell receptor. All body cells have surface receptors through which they interact with cells or soluble factors (e.g. cytokines) and which are involved in the immune response. There are receptors for cytokines, for growth factors, etc. T cells have more antigen receptors, which help them to recognise these when they are expressed by HLA molecules.

Cerebrospinal fluid. Colourless fluid which is composed partly of filtered substances from the blood and partly secretions released by brain cells, circulating around the cavities of the brain and spinal cord. Doctors use different techniques to study and detect abnormalities associated with multiple sclerosis.

Demyelination. Disappearance of the myelin sheath that surrounds the nerve fibres of neurons. It can be observed in certain diseases such as multiple sclerosis.

Experimental allergic encephalomyelitis (EAE). Multiple sclerosis is a disease unique to humans. Animals do not suffer from it. However, researchers have developed a similar disease in animals of different species (mouse, rat, guinea pig, monkey, etc.), in order to study multiple sclerosis in the laboratory. This disease induced in experimental animals is called experimental autoimmune encephalitis.

Fatigue. A feeling of lack of energy, exhaustion or tiredness that can accompany activity or which may exist even without exercise.

Gadolinium. A generic name given to a series of chemical compounds that contain this element. Used as a contrast agent in nuclear magnetic resonance imaging in order to improve image quality and highlight any abnormal tissue. In multiple sclerosis it helps differentiate between old and new lesions.

HLA. Acronym for “Human Leukocyte Antigen”. It’s the genetic name for the human major histocompatibility complex. The function of these molecules is to express antigens on the surface of cells so that they can be recognized by appropriate T cells. Thus, after interaction with the T cells, an immune response is initiated against this antigen. If the antigen is foreign (e.g. a virus), the response triggered will eliminate the virus from the body. If the antigen expressed by HLA molecules is a self-antigen (e.g. myelin) this will trigger an attack on the body itself.

Immunoglobulins (Ig). Immunoglobulins, or antibodies, are produced by B cells during the immune response. There are several types of immunoglobulins A, E, F, G and D. In many MS patients, when they have an autoimmune response within the central nervous system, immunoglobulins are produced, especially IgG. These immunoglobulins are those detected after a lumbar puncture, when the presence of oligoclonal bands is determined.

Immunosuppression. Weakening the body’s immune system and fighting infections and other diseases. Immunosuppression can be deliberately induced by drugs, or as a result of certain diseases such as AIDS or lymphoma, or cancer drugs. Many drugs that are being researched for the treatment of MS are immunosuppressants.

Interferons. Cytokines generated by the body in response to infection by viruses, and which are also involved in other types of immune responses. Interferon gamma greatly increases the number of HLA molecules in the membrane of cells, which enhances the recognition of antigens by T cells. In MS patients, it facilitates the recognition of antigens in the myelin sheath and can cause a worsening of the symptoms of the disease. Interferon alphas and betas probably have a suppressive effect on the immune system and may be beneficial in some patients for the treatment of multiple sclerosis.

Lesion. An abnormal change in the structure of an organ due to disease or injury.

Myelin. Fat that covers the nerve fibres of the brain and spinal cord allowing nerve impulses to be transmitted more quickly. In multiple sclerosis, the myelin is damaged through a process known as demyelination. This results in the nerve impulses being blocked.

Myelin basic protein (MBP). A major component of myelin. When myelin is affected (as in multiple sclerosis), MBP can often be found in abnormally high levels in the cerebrospinal fluid of the patient. When injected into laboratory animals, MBP induces experimental allergic encephalomyelitis (EAE), a chronic disease of the brain and spinal cord similar to multiple sclerosis.

Nuclear magnetic resonance (NMR). Radiologic examination that is a non-invasive way of obtaining images of the body on any plane and without emitting ionizing radiation. The various anatomical structures can be differentiated better than through using any other radiology examination. In multiple sclerosis it allows lesions to be observed and evaluated as they develop.

Oligodendrocytes. Cells that produce and maintain the myelin sheath in the brain and spinal cord

Paresthesias. Abnormal sensations such as numbness, tingling or itching that can occur anywhere on the body, but most often felt in the hands, feet, arms and legs.

Plaques. Discontinuous areas of inflammation and demyelination in the white matter of the brain and spinal cord, typical of multiple sclerosis. The plaques disrupt or block nerve signals that normally pass through the regions affected by the plaques.

Retrobulbar optic neuritis. Acute inflammation of the myelin sheath of the optic nerve which causes a rapid reduction in vision of the affected eye and pain in moving the eye. The most common causes are multiple sclerosis and viral infections but it is usually temporary.

Spasticity. The existence of muscle tension and weakness that limits the movement of the limbs. Refers to tight, stiff muscles with exaggerated deep tendon reflexes.

T Cells. Subpopulation of lymphocyte cells in the immune system which develop in the thymus gland. These cells contain receptors in the membrane that recognize antigens presented by HLA molecules. Once there is an interaction between the T cell and the antigen-presenting cell (that contains the HLA molecule with the peptide in its membrane), the T cell is activated and triggers an immune response against the antigen. If the antigen is a self-antigen (e.g. myelin), the T cell will trigger a response against myelin, producing cytokines. These are proteins produced by the cells (T cells and then the body’s cells) that affect the behaviour of other cells. They are involved in many biological processes. In multiple sclerosis, a cytokine is administered, interferon-beta, with the aim of reducing the inflammatory response in MS sufferers.

Transverse myelitis. Severe inflammatory and demyelinating disorder of the spinal cord that causes sudden pain in the lower back and muscle weakness, as well as abnormal sensory sensations in the lower limbs. Transverse myelitis often diminishes spontaneously, though severe cases can lead to permanent disability.

White matter. Part of the central nervous system consisting of nerve fibres covered with myelin. The nerve fibres contain axons in particular (an axon is the part of the neuron responsible for transmitting nerve impulses from one neuron to another via transmitter substances). In multiple sclerosis lesions occur in the white matter of the brain and spinal cord.