What is immunodeficiency?

Definition

The
immune system defends the body against infections.
The impairment or absence of the immune system results in immune deficiencies, or
immunodeficiencies, which increase susceptibility to infectious diseases and rare
cancers. A normal, healthy immune system confers lifelong protective immunity
against harmful toxins, viruses, fungi, bacteria, parasites, and cancer cells.
Immune deficiencies predispose a person to persistent and unusual infections,
slower healing, and increased incidences of rare cancers. Persons who have
immunodeficiency are considered immunocompromised.

For the immunocompromised person, opportunistic infections, especially if left undiagnosed or untreated, increase morbidity and mortality; these infections are typically harmless to a person with a healthy immune system. Because of complex and intertwined regulatory systems in the body, immunodeficiencies that affect either parts of the innate or acquired immune systems can easily lead to serious health complications, even when other parts of the immune system function normally.

Immunocompromised persons often have repeated infections that become serious.
Some immunodeficiencies will shorten a person’s life, while others, if properly
treated, will mainly affect a person’s short- or long-term quality of life.

A sore throat or head cold may lead to pneumonia. Severe burns are always
associated with complications because the injured skin has lost its mechanical
integrity and immune defense properties. Persons with acquired immunodeficiency
syndrome (AIDS) are especially susceptible to opportunistic
infections and can become critically ill from simple, normally nonthreatening
infections.

Medical procedures too are associated with an increased risk of infections.
Other complications might present themselves as autoimmune
disorders, slowed growth, increased risk of cancer, and
damage to lungs, the heart, the nervous system, and the digestive tract.

Congenital and Acquired Immunodeficiencies

Congenital (primary) immunodeficiency (CI) is evident at birth and generally results from genetic defects or disorders. These disorders are relatively rare and are classified based on the immune component that is affected, including B cells, T cells, B and T cells, NK cells, phagocytes, and complement proteins.

Acquired (secondary) immunodeficiency (AI) develops later in life and usually is the result of an infectious process, a complication of another condition or disease, or the use of certain drugs during treatment for another condition. AIs are more common than CIs. Malnutrition, some types of cancer, and infections are the most common causes for AIs. Typical infections that can result in AI are cytomegalovirus, lupus, chronic hepatitis, measles, chickenpox, tuberculosis, German measles (rubella), infectious mononucleosis (Epstein-Barr virus), and certain bacterial and fungal infections.

Certain types of drugs, such as anticonvulsants, immunosuppressants, corticosteroids, some monoclonal antibodies, and chemotherapy drugs, can cause an AI. For example, for tissue or organ transplantation, immunosuppressants are used to prevent organ rejection by intentionally suppressing the immune system. Similarly, immunosuppressants are used to reduce inflammation, as in the case of rheumatoid arthritis. In addition, radiation therapy and some chemotherapy drugs, which are given to treat cancer, destroy the cells of the immune system. Immunosuppressants repress the body’s ability to attack infections and, sometimes, to destroy cancer cells. During and sometimes beyond drug treatment, the chance of infection increases.

AI is common among severely sick, hospitalized, and older persons. Almost every
lengthy acute disorder or infection can potentially lead to an immunodeficiency.
In diabetes, white blood cells malfunction because of high
sugar levels in the blood, leading in some cases to AI. The best-known severe AI
is AIDS, which is caused by human immunodeficiency virus (HIV)
infection.

Prevention and Treatment

Treatments exist for preventing and treating infections, for boosting the immune system, and for treating underlying causes. Some immunodeficiencies can be prevented, to a certain extent. These include AIDS, cancer, and diabetes. The risk for HIV infection (and AIDS) can be lessened by avoiding the sharing of drug-injection needles and by practicing safer sex. Decreased use of immunosuppressants by persons with cancer might restore the normal function of the immune system after a successful treatment. In the case of diabetes, balanced blood sugar levels can improve the function of white blood cells and can, consequently, help to prevent infections.

The type of immunodeficiency determines preventive and treatment strategies.
Common prevention strategies include eating only cooked food, drinking bottled
water, taking one’s regular medications, proper vaccination, avoiding exposure to
other infectious people, and observing good personal hygiene. Infections can be
managed with antibiotics or with the treatment of symptoms.

Immunoglobulin, gamma interferon, and growth factors therapy can help boost the
immune system. To properly balance the complex immune regulation systems in the
body, immune-related treatments should be applied with careful knowledge of the
deficiency. In severe combined immunodeficiency syndrome (commonly known as
bubble-boy syndrome), stem cell transplantation can offer a permanent cure of this
life-threatening condition.

Impact

The impact of immunodeficiencies lies in the incidence and prognosis of many infectious diseases, which strongly affect the young, the ill, and the elderly with often devastating outcomes. More research is needed to quantify the impact of infectious disease on immunodeficiencies. Better understanding of the clinical indicators of immune competence may lead to improvements in the prevention, treatment, management, and outcome of infectious diseases and their affect on immunocompromised persons.

Bibliography

Al-Muhsen, S. Z. “Gastrointestinal and Hepatic Manifestations of Primary Immune Deficiency Diseases.” Saudi Journal of Gastroenterology 16 (2010):66-74.

Blaese, R. Michael, and Jerry A. Winkelstein. Patient and Family Handbook for Primary Immunodeficiency Diseases. 4th ed. Towson, Md.: Immune Deficiency Foundation, 2007.

De Bakker, P. I., and A. Telenti. “Infectious Diseases Not Immune to Genome-Wide Association.” Nature Genetics 42 (2010): 731-732.

Morimoto, Y., and J. M. Routes. “Immunodeficiency Overview.” Primary Care: Clinics in Office Practice 35 (2008): 159-173.

Sompayrac, Lauren M. How the Immune System Works. 3d ed. Hoboken, N.J.: Wiley-Blackwell, 2008.

Strugnell, R. A., and O. L. Wijburg. “The Role of Secretory Antibodies in Infection Immunity.” Nature Reviews Microbiology 8 (2010): 656-667.

Tolan, Robert W., Jr. “Infections in the Immunocompromised Host.” Available at http://emedicine.medscape.com/article/973120-overview.