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How can a weak immune system increase the risk of infection?

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Health monitoring — human disease The routine monitoring of blood pressure levels is an important part of assessing an individual's health. Blood pressure provides information about the amount of blood in circulation and about heart function and thus is an important indicator of disease.

A weak immune system, or immunodeficiency, increases the risk of infection by impairing the body's ability to defend against pathogens such as bacteria, viruses, fungi, and protozoa.12

The immune system relies on a complex network of components, including white blood cells (such as lymphocytes and phagocytes), antibodies, and complement proteins to identify and destroy invaders. When these mechanisms are defective—whether due to genetic mutations, cancer, poor nutrition, or immunosuppressive drugs—the body cannot effectively mount an immune response.3124

For example, HIV destroys helper T cells, leaving individuals susceptible to opportunistic pathogens that are typically harmless to those with healthy immune systems. By suppressing these critical defenses, immunodeficiency renders an individual unable to resist infections that would otherwise be easily cleared by the body.452