Immune deficiency is primarily caused by genetic mutations or acquired conditions that disrupt the normal functioning of the immune system.
Primary Immunodeficiency
Primary immunodeficiency disorders (PIDs) are often the result of genetic mutations. These mutations can affect various components of the immune system, such as:
- Antibody production: Mutations can prevent the body from producing enough antibodies to fight off infections.
- T cell function: Mutations can impair the ability of T cells to recognize and eliminate infected cells.
- Complement system: Defects in the complement system, a group of proteins that enhance the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, can lead to increased susceptibility to infections.
- Phagocyte function: Mutations affecting phagocytes (cells that engulf and destroy pathogens) can hinder their ability to fight off infections effectively.
Some genetic mutations are sex-linked, primarily affecting males. For example, if the mutated gene is located on the X chromosome, the resulting disorder is called an X-linked disorder, which occurs more frequently in males. Approximately 60% of people with PIDs are male.
Secondary Immunodeficiency
Secondary or acquired immunodeficiency occurs as a result of external factors such as:
- Infections: Certain infections, like HIV, directly attack and destroy immune cells, leading to severe immune deficiency (AIDS).
- Malnutrition: Severe malnutrition can impair immune cell development and function.
- Medications: Immunosuppressant drugs, often used after organ transplants or to treat autoimmune diseases, can suppress the immune system.
- Cancer treatments: Chemotherapy and radiation therapy can damage immune cells, leading to immunodeficiency.
- Certain cancers: Some cancers, like leukemia and lymphoma, directly affect immune cells and their function.
- Aging: The immune system naturally weakens with age (immunosenescence).
- Splenectomy: Removal of the spleen impairs the body’s ability to filter the blood and fight infections.
- Chronic diseases: Conditions like diabetes and kidney disease can weaken the immune system.
Summary
Immune deficiency arises from both genetic defects that disrupt immune system development and external factors that compromise immune function. Identifying the underlying cause is crucial for appropriate management and treatment.
