About Neutrophils
Neutrophils are the most abundant white blood cell and the immune system's frontline responders to bacterial and fungal infections — they engulf and destroy pathogens within minutes of arrival at an infection site. A high neutrophil count (neutrophilia) typically indicates an active bacterial infection, physical stress, steroid use, or inflammation; a low count (neutropenia) — most often caused by chemotherapy, viral illness, or autoimmune disease — impairs the ability to fight infection. The neutrophil-to-lymphocyte ratio is an emerging marker of systemic inflammation and cardiovascular risk.