Immune deficiency diseases are a group of diseases in which some components of immune system is missing or defective. Normally, the defense mechanism protects the body from invading pathogenic organism. When the defense mechanism fails or becomes faulty (defective), the organisms of even low virulence produce severe disease. The organisms, which take advantage of defective defense mechanism, are called opportunists. Immune deficiency diseases caused by such

opportunists are of two types:

1. Congenital immune deficiency diseases

2. Acquired immune deficiency diseases.


Congenital diseases are inherited and occur due to the defects in B cell or T cell or both. The common

examples are DiGeorge syndrome (due to absence of thymus) and severe combined immune deficiency (due to lymphopenia or the absence of lymphoid tissue).


Acquired immune deficiency diseases occur due to infection by some organisms. The most common disease of this type is acquired immune deficiency syndrome (AIDS).

Acquired Immune Deficiency Syndrome (AIDS)

AIDS is an infectious disease caused by immune deficiency virus (HIV). A person is diagnosed with

AIDS when the CD4 count is below 200 cells per cubic millimeter of blood. AIDS is the most common problem throughout the world because of rapid increase in the number of victims. Infection occurs when a glycoprotein from HIV binds to surface receptors of T lymphocytes, monocytes, macrophages and dendritic cells leading to the destruction of these cells. It causes slow progressive decrease in immune function, resulting in opportunistic infections of various types. The common opportunistic infections,

which kill the AIDS patient are pneumonia (Pneumocystis carinii) and malignant skin cancer (Kaposi sarcoma). These diseases are also called AIDS-related diseases. After entering the body of the host, the HIV activates the enzyme called reverse transcriptase. HIV utilizes this enzyme and converts its own viral RNA into viral DNA with the help of host cell DNA itself. Now, the viral DNA gets incorporated into the host cell DNA and prevents the normal activities of the host cell DNA. At the same time, the HIV increases in number inside the host’s body. The infected host cell ruptures and releases more

number of HIV into the bloodstream. After exposure to HIV, no symptoms develop for several weeks. This is the incubation period. The patient develops symptoms only when sufficient number of infected cells is ruptured. The common symptoms are fatigue, loss of weight, chronic diarrhea, low-grade fever, night sweats, oral ulcers, vaginal ulcers, etc. This phase prolongs for about three years before the disease is diagnosed. contaminated blood transfusion, contaminated needles or other invasive instruments, transmission from mother to fetus during pregnancy, transmission from mother to child during delivery or breastfeeding and vaginal sexual intercourse.


Prevention of AIDS is essential because the authentic treatment for this disease has not been established so far. Progress in the development of effective treatment is very slow. Moreover, the maximum duration of survival after initial infection is only about 10 to 15 years. So, it is necessary to prevent this disease.

Following safety measures should be followed to prevent AIDS:

1. Public must be educated about the seriousness and prevention of the disease.

2. HIV infected persons should be educated to avoid spreading the disease to others.

3. Blood should be screened for HIV before transfusion.

4. Intravenous drug users should not share the needles.

5. Pregnant women should get the blood tested for HIV. If the mother is infected, the treatment with

zidovudine may reduce incidence of infection in infants. The baby must be given zidovudine for 6

weeks after birth.

6. Young adults and teenagers must be informed about the safer sex techniques and use of condoms.

The need for limitation of sexual partners must be emphasized.

Mode of transmission

The HIV infection spreads when secretions from the body of infected individual come in contact with blood of the recipient through the damaged skin or mucous membrane.

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