Have you ever heard of the term immune-mediated disease? Maybe you’ve heard this term used in regard to multiple sclerosis (MS). Many people will also refer to MS as an autoimmune disease — which begs the question: Is an autoimmune disease the same thing as an immune-mediated disease?
The two terms are related. Immune-mediated diseases are conditions caused by abnormal activity of the immune system. This can include an overreaction from the immune system. For example, hypersensitivity, otherwise known as allergies, is sometimes considered an immune-mediated disease. Abnormal activity of the immune system can also include an attack on the body’s own tissues (autoimmunity). In this way, autoimmune diseases are included as a subset of immune-mediated diseases.
The type of immune-mediated autoimmune disease that may affect someone depends on the type of tissues the immune system attacks. The tissues that are under attack will also affect the symptoms the person experiences.
For example, in MS, immune cells attack components of the central nervous system, which includes the brain, spinal cord, and optic nerves. This attack leads to symptoms affecting motor and cognitive function.
For type 1 diabetes, the body forms an immune response against cells that make insulin in the pancreas. This attack results in an insulin deficiency, which leads to difficulty regulating blood sugar levels.
Immune cells can also attack the joint tissue, leading to damage, inflammation, and pain in those areas. This is what occurs during rheumatoid arthritis.
Another immune-mediated disease is systemic lupus erythematosus, or lupus. In lupus, immune cells can attack the tissues of many body parts, including the joints, skin, kidneys, and blood vessels, leading to rashes and a range of other symptoms.
These autoimmune diseases represent just a few of the types of immune-mediated autoimmune disorders that attack the body’s own tissues.
The classification of MS as an immune-mediated disease means that the immune system plays a role in the cause of this demyelinating condition. While the exact cause of MS is unknown, the immune system is known to play a role in destroying the myelin sheath that covers nerve cells. Lesions on the myelin sheath affect the way that nerve cells, known as neurons, communicate with each other to transmit sensory, cognitive, and motor information to other cells in the body. The destruction of the protective myelin sheath can lead to the formation of lesions in the central nervous system and symptoms such as difficulty with cognitive and motor activities.
But what sparks the autoimmune attack against the central nervous system? It is not yet completely understood, but it’s thought that the immune system makes a mistake and responds to molecules in the body known as self-antigens.
Antigens are the molecules or substances that the immune system can recognize. In a healthy person, the immune system knows how to tell the difference between self-antigens and foreign antigens. This ability to tell the difference so the immune system doesn’t attack itself is referred to as immune tolerance. When the immune system loses immune tolerance against self-antigens, autoimmunity can occur.
Lymphocytes are immune cells that are thought to be involved in the development of MS. There are two main types of lymphocytes: B cells and T cells. B cells are responsible for making immunoglobulins, or antibodies. Antibodies are proteins B cells secrete to stick to foreign antigens and help destroy them. In MS, B cells may secrete autoantibodies that stick to self-antigens and cause their destruction.
B cells can also activate T cells to respond against self-antigens. T cells that respond to self-antigens can secrete inflammatory molecules known as cytokines. These substances can damage the myelin sheath and lead to its destruction.
Macrophages are another immune cell type involved in the development of MS. In MS, these cells can promote inflammation in the central nervous system, contributing to neurodegeneration.
More evidence for MS being an autoimmune disease includes the genes that are associated with the disease. One gene associated with MS is the human leukocyte antigen (HLA) gene HLA-DRB1. This gene is important for T-cell activation, and people with a specific version of the gene (HLA-DRB1*15:01) are three times more likely to develop MS compared to individuals who do not carry the gene.
Several other immune-related gene variations, such as certain cytokine receptor genes, are also associated with the development of MS.
The use and success of immunomodulatory drugs for the treatment of MS also provides evidence that the immune system is involved in the development of MS. For example, drugs like Ocrevus (ocrelizumab), a therapy that works by depleting B cells, can be successful.
Understanding the immune system and how it is involved with MS can help you learn more about your disease and how to manage it. Immunology is a fast-paced and quickly evolving field. Experts are learning more about immune-mediated diseases all the time. As researchers learn more about the immune system and how it is involved with MS, they may develop better and more effective treatment options for people living with MS.
MyMSTeam is the social network for people with MS and their loved ones. On MyMSTeam, more than 167,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.
Are you living with MS? Share your experience in the comments below, or start a conversation by posting on MyMSTeam.