Immune System Disorders

Overview of immune system disorders

The primary responsibility of the immune system is to protect the body from diseases. The immune system works by producing specific antibodies against the invading antigens. Some important proteins, namely the Immunoglobulin proteins also play a significant role in immunity. But under certain predisposing conditions, the immune system of the body attacks the body cells instead of protecting them. This pathological condition mainly arises from various genetic factors and is known as “immune system disorder”.

What are immune system disorders?

Immune system disorders or autoimmune disorders are a group of diseases that occur when the immune system of the human body attacks the body cells instead of protecting them.

Under normal conditions, the immune system identifies the foreign particles within the body (virus, bacteria or other pathogens) and destroys them. But in some cases, the immune system mistakes the body cells for harmful antigens and attacks them.

This results in the destruction of the cells and tissues in that part of the body. This, in turn, leads to malfunctioning of the specific organ that results in some major immune system disorders. Medical conditions of lesser intensity may arise from the anomalous functioning of the immune system. These are known as “allergies”.

How does the immune system work?

Two primary groups of cells are responsible for body immunity. These are as follows-

• B-cells: B-cells comprise of the different immunoglobulins and antibodies like- IgA, IgD, IgE, IgG and IgM. In a healthy person, these cells provide protection against different pathogens. But in certain diseases, hyperactivity or hypoactivity of these antibodies occurs. In the hyperactive state, the concentration of the immunoglobulins increases abnormally. This occurs either as an inflammatory response or due to some chronic infections like cancer. In the hypoactive state, the concentration of the immunoglobulins decline sharply. This is usually common in certain immunosuppression states such as- agammaglobulinemia or hypogammaglobulinemia.
• T-cells: Three primary types of T-cells are present in the body namely- helper cells, cytotoxic cells and the suppressor cells. The helper T cells co-ordinate the immune response. The cytotoxic cells help in the elimination of the infected cells from the body. The suppressor cells help in the suppression of the abnormal immune response.

Functional abnormalities of any of these cells may arise due to genetic and environmental factors. This leads to immune system disorders.

Genetics of immune system disorders

Mutations in certain genes are responsible for autoimmune diseases. Given below is a list of such genes-

• AIRE: This gene results in Autoimmune Polyendocrine Syndrome. In this condition, the T-cells escape the thymic negative selection due to abnormalities in the expression of the self-antigens present in the thymus.
• FOXP3: The diseases occurring, in this case, are- Enteropathy, Polyendocrinopathy, X-lined Syndrome (IPEX) and immune dysregulation. These diseases arise from the reduction in the generation of the regulatory T cells, CD4+ cells and the CD25+ cells.
• FAS: This gene leads to a disease known as Autoimmune Lymphoproliferative Syndrome (ALPS). This results due to the apoptotic death of the reactive B and T cells.

These genetic factors may also combine with certain environmental triggers and disease-causing pathogens to lead to immune system disorders.

What are the different types of immune system disorders?

The autoimmune disorders may attack the different parts of the body and elicit immune response. The different types of the immune system disorders will be discussed in separate sections.

Rheumatoid arthritis

It is a type of symmetric inflammatory disease in which swelling and inflammation of the small bones present in the hands and feet occur.

The main factors behind this disease are irritation of the nerve endings and overstretching of the capsules due to swelling of the respective joints.

The joints that are affected in this disease are- the cervical spine, the joints of the hand and wrists, feet and ankle joints, elbow and shoulder joints and the temporomandibular joints.

Rheumatoid arthritis has the following subtypes-

• Seropositive Rheumatoid Arthritis
• Felty’s syndrome
• Rheumatoid vasculitis

Grave’s disease

It is also known as “toxic diffuse goitre”. An abnormal enlargement of the thyroid gland occurs in this condition. The immune system generates a particular antibody known as Thyroid Stimulating Immunoglobulin (TSI). The TSI attaches itself to the thyroid gland and emulates the actions of the Thyroid Stimulating Hormone (TSH) for a long time. This causes overproduction of the thyroid hormones (Thyroxine and Triiodothyronine). Bulging out of the eye-balls and double vision also occur in this disease.

Celiac disease

Celiac disease is a type of gastrointestinal disorder in which the consumption of gluten-containing food products leads to the inflammation of the inner lining of the small intestine. This results in the malabsorption of Vitamins A,D,E,K, iron and calcium across the small intestine.

Celiac disease is of four types-

• Silent
• Latent
• Typical
• Atypical
• Non-responsive

Hemolytic anemia

This is a hemoglobin deficiency disease in which destruction and elimination of the red blood cells (RBCs) occurs even before their normal lifespan of 120 days. This disease is often manifested as- Cholelithiasis, Reticulocytosis and jaundice. It has two subtypes-

• Warm hemolysis (caused by IgG autoantibodies)
• Cold hemolysis (caused by IgM autoantibodies)

Type I diabetes

In this disease, autoimmune destruction of the pancreatic beta cells occurs. This leads to a decline in insulin production and a consequent increase in the blood-glucose level.

Psoriasis

Psoriasis is a type of skin disease in which large portions of the skin suffers from inflammation, patchiness and redness along with the formation of reddish, scaly plaques.

Diagnosis

The following diagnostic tests may be helpful-

• Blood test (CBC)
• Swab test
• Skin biopsy
• TSH test
• Ultrasonography

Treatment and prevention

The exact treatment method used for treating immune system disorders depends upon the type of immune system disease. For example, immunodeficiency state such as in case of HIV/AIDS is treated with the help of antiretroviral medications. Other conditions are treated with the help of antibiotics and immunoglobulin therapy. In extreme cases, where the bone marrow becomes incapable of producing adequate lymphocytes, a bone marrow transplant may be required.

There are no ways to prevent primary ( hereditary) immune system disorders. For acquired immune system disorders, the following steps can be taken to reduce the onset of infections:

• Practice proper hygiene and sanitation.
• Consume healthy and home cooked food. Avoid street and outside food at any cost.
• Get vaccinated for infections.
• Avoid contact with other infected individuals.
• Maintain physical fitness by having a regular exercise routine.

References