The function of the immune system is to protect against infections and helps in the process of healing and repair. Sometimes, the immune system fails to protect the body against diseases and malignancies a condition called immunodeficiency. There are two categories of immunodeficiency diseases based on origin: primary and secondary immunodeficiency diseases.

Primary immunodeficiency (PI) disorders also called congenital immunodeficiencies are genetic and are present at birth. The affected miss parts of the immune systems or have faulty defense mechanisms due to genetic defects. They are much rare than the secondary immunodeficiency disorders. Most of them manifest at infancy and childhood (Greenberg, 2008). Individuals with PI disorders are highly susceptible to infections. The infection depends on the immunodeficiency itself.

For instance, B cell deficiency characterized by few or absent IgM, IgG lead to susceptibility to Pneumococcal, Streptococcal and Haemophilus infections of the lungs, skin and CNS in early childhood stages (Greenberg, 2008). The few B cells do not produce enough antibodies to fight these pathogens. Secondary immunodeficiency disorders are not genetic. One acquires these disorders later in life.

Some secondary occurrences or factors cause a decrease in the immune system’s response to diseases. Some of these causes include malnutrition, viral infection, irradiation, cytotoxic drugs, corticosteroids, aging and organ childhood (Greenberg, 2008). These disorders are common. The most notable example is AIDS (Acquired Immuno-Deficiency Syndrome) caused by infection with Human Immunodeficiency Virus (HIV). The virus destroys cells of the immune system leading to high susceptibility to diseases. Autoimmunity is the breakdown of tolerance mechanisms and induction of immune response against the body’s own normal constituents.

The immune system may fail to recognize the body’s normal component as “self” and attacks the cells, tissues or organs causing an inflammation or complete damage. When this happens, an autoimmune disease occurs. One example of autoimmune disorders is rheumatic fever where the immune system attacks the “self” cells that have components resembling that of the pathogens. Another autoimmune disease is asthma. It results when allergens cause an inflammatory response that cause clogging of the respiratory pathways (Gillespie & Stephen, 2006).