Neutrophils play important roles in host defense against infectious agents but, paradoxically,
they are also involved in the pathology of various inflammatory conditions. Their
microbicidal armory consists of oxidative and nonoxidative processes that are activated
simultaneously upon phagocytosis. While destruction of infectious agents occurs intracellularly,
release of cytotoxic molecules into the extracellular milieu can damage body tissues.
Neutrophils are not a homogeneous cell population. Subpopulations exist in various
stages from dormant to primed to fully activated. The activities of neutrophils are
modulated by cytokines, hormones and bioactive lipids. As neutrophils represent 60
% of the circulating leukocyte pool, they are readily accessible to experimental investigation.
The sequence of events that occurs in the neutrophil response to microbial invasion
includes adherence, chemotaxis, phagocytosis, the oxidative burst, degranula-tion
and microbial killing. In general, high-intensity exercise suppresses most neutrophil
functions both acutely and chronically while the effects of moderate exercise have
bee n conflicting. This review will summarize where the field is now and present some
suggestions for future research. Emphasis will be placed on resolving conflicting
results that may be due to biological and technical variability, and determination
of the regulatory events that may mediate exercise-induced changes in neutrophil function.
Key words
Infection - inflammation - immunoregulation - athletes - sport
