Being Immunocompromised or Having an Immune Deficiency

A person is said to have an immune deficiency or be immunocompromised when their immune system is incapable of working at full capacity. It is the opposite of being immunocompetent. The immune system is how the body fights off diseases and protects itself against new infections. Therefore, someone who is immunocompromised will usually get sick more often, stay sick longer, and be more vulnerable to different types of infections.

Your immune system is responsible for protecting your body against infections. Several organs are part of your immune system, including your spleen, tonsils, bone marrow, and lymph nodes. Together, these organs work together to create immune cells, otherwise known as white blood cells, and antibodies.

There are two complementary systems in the immune system, innate immunity, and adaptive immunity. Innate immunity is immunity people are born with. It does not respond to specific pathogens as much as it responds to specific types of threats. Adaptive immunity is what most people think of when they think of the immune system. This is the part of the immune system that learns to respond to specific antigens -- either through exposure to an infection or through vaccination.

Primary immunodeficiency is immunodeficiency you are born with. These types of immunodeficiency can be inherited from generation to generation. They can also occur spontaneously. In contrast, a secondary immunodeficiency is caused by exposure to something else. This can be a disease, like HIV. It can also be an accident or operation, such as one that damages the spleen.

Most immunodeficiencies affect the adaptive immune system. However innate immunity can also be affected by immunodeficiency.

There are many conditions that can lead to a person becoming immunocompromised.

• Acquired immune deficiency syndrome (AIDS): Part of the definition of AIDS is that people with the disease are immunocompromised. That immune deficiency is one of the signs that separates a person with AIDS from someone who is merely infected with HIV. People with AIDS are susceptible to opportunistic infections that people with healthy immune systems would generally be capable of fighting off. This is because a specific type of immune system cells, CD4 cells, are reduced in number when the virus is active. When a person infected with HIV has a CD4 cell count that is below 200 cells per millimeter they are defined as having AIDS.
• Chemotherapy: The agents used to attack cancer cells also affect any actively dividing cells, including those in the bone marrow that produce the white blood cells that are a key part of the immune system. White blood cells counts often drop for people undergoing chemotherapy.
• Cancer: Certain cancers can cause a person to become immunocompromised even without chemotherapy. These include leukemia and lymphoma, in which cancerous white blood cells crowd out functioning white blood cells.

When a person is immunocompromised they are more susceptible to infections. The major sign of having an immunodeficiency is getting repeated or serious infections that are rare, or that only cause minor problems, in the general population. For example, people who are immunocompromised often get more serious, and more frequent, yeast infections. People with AIDS are more likely to be diagnosed with rare cancers, such as Kaposi's sarcoma.

There are also degrees of immune deficiency. Some people simply take longer to fight off common infections, whereas others must be protected from any disease exposures because even a normally mild condition could put their life at risk.

If your doctor is worried you might have an immune deficiency, they will probably want to do a number of tests. In addition, they will probably ask for a detailed medical history to determine if you've had the repeated infections that can be a hallmark of an immune disorder. The blood tests will likely include a white blood cell count, a T-cell count, and a check of your antibody (immunoglobulin) levels. Your doctor may also attempt to vaccinate you to see if the vaccine causes your body to produce protective antibodies. If it does not, that may be because of an immune deficiency.

Diagnosing that a person has an immunodeficiency is different from diagnosing its cause. Diagnosing the cause of an immunodeficiency can range from looking for an infectious disease, such as HIV, to genetic testing, to cancer screening. There are a number of conditions that can lead to immunodeficiency, and the diagnostic pathway for each one is different.

Depending on the reason a person is immunocompromised, the deficiencies in their immune system may be temporary or permanent. In many cases, it is possible for a person's immune system to return to nearly full function. For example, successfully treating HIV can restore the immune system. However, with a primary immunodeficiency, treatment options may be more limited.

In general, it's the cause of the immunodeficiency that's treated, not the immunodeficiency itself. One treatment for immunodeficiency may be a bone marrow transplant. However, that's only an appropriate treatment for individuals whose bone marrow isn't producing enough immune cells.

When the immunodeficiency itself isn't treatable, there are still other options. For example, there are therapies available that can help individuals fight off certain infections. You may also be more likely to need antibiotics or antiviral medications to fight diseases that immunocompetent people can ward off without treatment.

One of the questions many people have about HIV infection is whether it always leads to someone being immunocompromised. The answer is no. With early and effective treatment, people can live long healthy lives with HIV infection and show no clinical signs of an immune deficiency.