What Does Being Immunocompetent Mean?

Scientifically, to be immunocompetent simply means that the immune system is working properly and that the body is capable of mounting an appropriate immune response, when necessary.

A person can be immunocompetent or immunodeficient (where the immune system is not working as it should be), but not both at the same time.

Man sick in bed with a cold
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The Immune System

All organisms have developed complex immune systems that protect against infectious diseases. To function properly, the body's immune system must be able to recognize foreign intruders (i.e. pathogens such as bacteria, viruses, and parasites) and send defenders to fight the invading pathogen. Our genes determine what specific foreign substances our immune system will be able to recognize and resist (not pathogens).

Since pathogens can quickly change and adapt, they can sometimes avoid detection by the immune system. When this happens, you can feel sick, run down, and have a hard time fighting off the illness that has taken over your body.

Fortunately, your immune system has many different defense mechanisms and responses to recognize and neutralize pathogens. Your immune system can respond to pathogens in 2 ways:

  • Cell-mediated immune response where T-lymphocytes (or T-cells—a type of white blood cell) play a central role in recognizing and binding to certain cells such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens (antigens are proteins found on pathogens).
  • Humoral immune response of the B-lymphocytes (or B-Cells) and plasma cells (white blood cells that secrete large amounts of antibodies) protects against bacteria and viruses in the fluids of the body by "remembering" the invaders and producing antibodies to fight them (this is how you build immunity to some viruses after receiving a vaccine for that particular virus).

When T cells and B cells bind with recognized antigens, they become fully immunocompetent.

What If You Are Not Immunocompetent?

The opposite state of being immunocompetent is immunodeficiency or immuno-incompetent or immunocompromised. There may be some instances of overlap, but the following terms all describe an immune system that is not fully functioning in the following ways:

  • Immunodeficient: Such as a newborn baby boy whose immune system is not yet fully functioning, but may have had antibodies transmitted to him by his mother.
  • Immuno-incompetent: Such as cancer patients with a failed or failing immune system. Physicians often recommend that relatives and close contacts of those with immuno-incompetence should be vaccinated for a series of common diseases.
  • Immunocompromised: Transplant recipient patients that take anti-rejection medication so their body will not reject the donated organ are referred to as being immunocompromised.

Patients with any of the above listed immune system problems should not receive live, attenuated vaccines, be it viral or bacterial. Also, inactivated vaccines usually only offer full benefits to immunocompetent patients.

Autoimmune Disorders

When the immune system is compromised, there can be serious consequences. Normally, the immune system only reacts to invaders (not to antigens from a person's own tissues) but sometimes the immune system can malfunction and read the body's own tissues as foreign. This causes the immune system to have an autoimmune reaction, where it produces antibodies (called autoantibodies) or immune cells that attack the body's own tissues.

If enough autoantibodies are created, the body can damage tissue and cause inflammation, constituting an autoimmune disorder. For most people, such small amounts of autoantibodies are produced that an autoimmune disorder does not occur. For others, they may develop into one of the many autoimmune disorders, such as:

Further testing by a physician would be required to properly diagnose autoimmune disorders.

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  • Children's Health and the Environment. October 2011. WHO Training Package for the Health Sector World Health Organization. 
  • Peter J. Delves. Autoimmune Disorders. Merk Manuals.