Immune System Diseases

The Immune System

The immune system is a very complex one. It is protective in nature. Its role is to protect the organism from pathogenic microorganisms. This article will briefly describe the main diseases that affect the immune system.

The main immune system diseases can be classified as follows:

  1. Immunodeficiencies
  2. Autoimmunity
  3. Hypersensitivities


Immunodeficiency, also known as the immune deficiency is a state in which 1 or more of the components of the immune system are not active. In other words, the body’s immune system is unable to fight pathogens.

This specific disease can be either secondary (acquired) or primary (born with).

Secondary immunodeficiency can be acquired by patients who are about to receive a transplant (to avoid rejection of the donor’s organ) or by people whose immune system is over-active.

This disease also “naturally” occurs in some people after the age of 50. This phenomenon is known as immunosenescence.

Other factors that encourage immunodeficiencies:

  • Obesity
  • Consuming an excess of alcohol regularly
  • Malnutrition, especially in diets having a deficiency in protein


Autoimmunity is a condition whereby the body fails to differentiate between itself and foreign bodies. This results in attacks to its own cells and tissues. The cause of this disease is also sometimes due to a lower rate of multiplication of germs than expected, leading the immune response to the body’s own cells.


Hypersensitivity is an immune system disease that involves unwanted and unpleasant reactions produced by the normal immune system. These reactions may range from being mildly uncomfortable, to causing tissue and organ damage to causing death.

Hypersensitivity falls under 4 main categories:

Type I – Allergy

Mediators: lgE, lgG4

Type II – Cytotoxic

Mediators: lgM, lgG

Type III – Immune complex disease

Mediators: lgG

Type IV – Delayed-type hypersensitivity

Mediators: T-cells

Type V – Autoimmune disease (not always used)

Mediators: lgM, lgG

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