immunocompromised
Meaning of immunocompromised: Not one condition but many, and which part of the defense is missing predicts which organisms end up causing trouble.
Definition of immunocompromised
Immunocompromised describes a person whose immune defenses are weaker than normal, so infection is easier to acquire and harder to clear. The weakness may lie in the number or function of white blood cells, in antibody production, or in another part of the system. It can be temporary, as during a course of chemotherapy, or lifelong.
What causes it?
| Cause | Part of the defense affected |
|---|---|
| Chemotherapy and some cancers | Numbers of infection fighting white cells fall |
| Anti-rejection drugs after transplant, long courses of steroids | T cell activity is deliberately suppressed |
| HIV infection | A specific group of T cells is destroyed over time |
| Removal of the spleen, or blood cancers affecting B cells | Antibody defense against certain bacteria weakens |
| Inherited immune deficiencies | Varies with the specific defect, often present from childhood |
| Malnutrition, poorly controlled diabetes, organ failure, advanced age | General decline in several defenses at once |
Some of these are the intended effect of treatment rather than a failure of it. Suppressing the immune system is exactly how a transplanted organ is kept from being rejected, so the resulting vulnerability is a trade that comes with the therapy.
Why do infections look different?
Two things change. Organisms that healthy defenses brush aside are able to establish themselves, which is what opportunistic infection means, and familiar organisms cause more severe illness that spreads faster. Less obviously, the usual signs of infection can be muted or absent. Redness, swelling, pus and much of the fever are produced by immune activity itself, so when that activity is reduced the outward signs shrink with it. A serious infection can therefore present with little more than fatigue, confusion or a slight temperature.
Does it change how vaccines work?
It can. A vaccine works by training the same adaptive machinery that is impaired, so the response may be weaker and fade sooner. The type of vaccine also matters. Preparations built from a killed organism, a purified fragment or genetic instructions contain nothing that can multiply, while vaccines using a live weakened organism rely on that organism replicating in a controlled way, which is a different proposition when defenses are reduced.
Used in a sentence
The immunocompromised patient was monitored closely for signs of infection during treatment.
Good to know
An immunocompromised state can follow from disease or from treatment aimed at a different goal, such as preventing transplant rejection, so the underlying cause shapes both the degree and the pattern of vulnerability to infection.