The immune system is the body’s network of cells and organs that is specially developed for fighting off infections. Weaknesses in the immune system can be either congenital, meaning someone is born with them, or acquired, caused by outside factors. A person with decreased immunity is at an increased risk for infections and illnesses.
If you are experiencing serious medical symptoms, seek emergency treatment immediately.
The immune system is very complex, and contains numerous types of cells and proteins that function to fight off infections and keep the body healthy. A defect or mutation in any one of these components can lead to a congenital immunodeficiency, also referred to as a primary immunodeficiency 4. The most common defect is IgA deficiency, which can happen as often as 1 in 333 people, and is often asymptomatic; however, patients can also experience frequent sinus, urinary tract and intestinal infections. The other extreme of primary immunodeficiency is severe combined immunodeficiency, or SCID, which affects 1 in 50,000 people. In this condition, there is a problem with the body generating T cells, and mature T cells do not develop. This leads to severe life-threatening infections, especially from viruses and fungi. Babies born with SCID require a bone marrow transplant for survival. Hundreds of other primary immunodeficiencies have been described that fall somewhere in between these two in terms of clinical severity, and many more have yet to be discovered 4.
Immunodeficiency Due to Viruses
What Is the Function of B12 in the Body?
Human Immunodeficiency Virus, or HIV, was characterized in the early 1980s. HIV is a virus that infects human T helper cells and leads to an inability to fight off viruses and certain parasites. As of 2006, one in 5000 people in the U.S. were infected with the virus, while in some African countries, the prevalence was roughly one in five people. The treatment for HIV is combination therapy with highly active antiretroviral therapy, or HAART, which typically includes three different drugs. This drug regimen has greatly improved long-term survival for patients with HIV and slows the progression to AIDS, acquired immunodeficiency syndrome 3. Another virus that can cause severe acquired immunodeficiency is human T-lymphotrophic virus, or HTLV, which is most common in Japan and other parts of Asia. Other viruses like Epstein-Barr virus, which causes mononucleosis, and cytomegalovirus can interfere with the body's normal immunity, but the impact is typically not as severe.
- Human Immunodeficiency Virus, or HIV, was characterized in the early 1980s.
- Another virus that can cause severe acquired immunodeficiency is human T-lymphotrophic virus, or HTLV, which is most common in Japan and other parts of Asia.
Immunodeficiency Due to Malnutrition
Deficiency in certain vitamins and minerals can lead to decreased immune system function. Vitamins A, E and C, along with zinc, copper, iron and selenium, have all been shown to be important for either neutrophil, T cell, or antibody function. People with a poorly balanced diet and those with intestinal disease causing decreased absorption of nutrients are at risk.
Immunodeficiency Due to Other Diseases
Infections Caused by Multiple Myeloma
Women affected with Turner’s Syndrome can have low antibody levels, poor T cell function and problems with neutrophil-mediated killing of bacteria. Down's syndrome can cause similar problems. People who suffer from sickle cell disease invariably lose the function of their spleen over time, and this puts them at risk for streptococcal pneumonia and salmonella bone infections. Cystic fibrosis patients have difficulty clearing mucous from their lungs, leading to a high risk of pneumonia, especially with Pseudomonas organisms.
- Women affected with Turner’s Syndrome can have low antibody levels, poor T cell function and problems with neutrophil-mediated killing of bacteria.
- Cystic fibrosis patients have difficulty clearing mucous from their lungs, leading to a high risk of pneumonia, especially with Pseudomonas organisms.
Other Factors Causing Low Immunity
Stress has been shown to modulate the function of immunologic signaling molecules, but this effect varies greatly from one person to another. Aging also appears to have a negative impact on immunity. Exposure to extreme environmental conditions, such as space flight, high altitudes and ionizing radiation, can impair the body’s normal ability to fight off infections as well.
What Is the Function of B12 in the Body?
Infections Caused by Multiple Myeloma
Characteristics of Enterococcus Faecalis
Reasons for a Low Hemoglobin Count
Diseases That Lower White Blood Cells
Bone Eating Diseases
Antibiotics That Affect Bacterial Cell Structure
Cell Membrane Diseases
What Are the Causes of Low White Blood Cell Count & Weight Loss?
Disorders of the Thymus Gland
- “Pediatrics”; The T-, B-, and NK-Cell Systems; Rebecca H. Buckley; August, 2007.
- “Clinical Immunology Principles and Practice”; Immunodeficiency Due to Congenital, Metabolic, Infectious, Surgical, and Environmental Factors; Javier Chinen and William T. Shearer; 2008.
- “Clinical Immunology Principles and Practice”; HIV Infection and Acquired Immunodeficiency Syndrome; Christopher S. Baliga, Mary E. Paul, Javier Chinen and William T. Shearer; 2008.
- “Clinical Immunology Principles and Practice”; Primary T-cell Immunodeficiencies; Francoise Le Deist and Alain Fischer; 2008.
- “Journal of Neurology”; Psychoneuroimmunology--Cross-talk between the Immune and Nervous Systems; T. Ziemssen and S. Kern; May 2007.
- Chaplin DD. Overview of the immune response. J Allergy Clin Immunol. 2010;125(2 Suppl 2):S3–S23. doi:10.1016/j.jaci.2009.12.980
- Semango, G.P., Charles, R.M., Swai, C.I. et al. Prevalence and associated risk factors for Kaposi’s sarcoma among HIV-positive patients in a referral hospital in Northern Tanzania: a retrospective hospital-based study. BMC Cancer 18, 1258 (2018) doi:10.1186/s12885-018-5155-2
- Meidani M, Naeini AE, Rostami M, Sherkat R, Tayeri K. Immunocompromised patients: Review of the most common infections happened in 446 hospitalized patients. J Res Med Sci. 2014;19(Suppl 1):S71–S73.
- McCusker C, Upton J, Warrington R. Primary immunodeficiency. Allergy Asthma Clin Immunol. 2018;14(Suppl 2):61. Published 2018 Sep 12. doi:10.1186/s13223-018-0290-5
- Chinen J, Shearer WT. Secondary immunodeficiencies, including HIV infection. J Allergy Clin Immunol. 2010 Feb;125(2 Suppl 2):S195-203. doi:10.1016/j.jaci.2009.08.040.
- Lehman H, Hernandez-Trujillo V, Ballow M. Diagnosing primary immunodeficiency: a practical approach for the non-immunologist. Curr Med Res Opin. 2015 Apr;31(4):697-706. doi:10.1185/03007995.2014.1001063.
- Lin JN, Lin CC, Lai CH, Yang YL, Chen HT, Weng HC, Hsieh LY, Kuo YC, Lauderdale TL, Tseng FC, Lin HH, Lo HJ. Predisposing factors for oropharyngeal colonization of yeasts in human immunodeficiency virus-infected patients: a prospective cross-sectional study. J Microbiol Immunol Infect. 2013 Apr;46(2):129-35. doi:10.1016/j.jmii.2012.07.009.
- Raje N, Dinakar C. Overview of Immunodeficiency Disorders. Immunol Allergy Clin North Am. 2015 Nov;35(4):599-623. doi:10.1016/j.iac.2015.07.001.
- Szabolcs P, Cavazzana-Calvo M, Fischer A, Veys P. Bone marrow transplantation for primary immunodeficiency diseases. Pediatr Clin North Am. 2010 Feb;57(1):207-37. doi:10.1016/j.pcl.2009.12.004.
Amy O'Connell is a writer who has published research in scientific journals such as "Infection and Immunity." Her areas of expertise include allergies, conditions in children and celiac disease. She has a Ph.D. in immunology and a medical degree from Thomas Jefferson University in Philadelphia.