[Study of neutrophil dysfunctions in the elderly using a chemiluminescence method]

To evaluate the cause of the vulnerability to infections in the elderly, the ability of neutrophil to generate reactive oxygen species was assessed by a luminol-dependent chemiluminescence (CL) assay after stimulation with non-opsonized zymosan, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Candida albicans and lumispheres in elderly patients aged 70 to 93 years. The integrated CL for 20 minutes of whole blood and neutrophils induced by zymosan in the elderly was significantly lower than that in healthy young adults, and the integrated CL of neutrophils induced by lumispheres was also significantly lower in the elderly aged 80 years and over. When bacterial infection occurred in the elderly, the levels of CL were elevated and decreased in the convalescence. This response is proper for host-defense mechanism against infection. However, whole blood CL response was not fully activated in any patients of the elderly during bacterial infection. In these cases lower white blood cell counts, lower neutrophil counts, or the decreased level of the serum total protein, albumin, total cholesterol or cholinesterase were observed. Relationship between malnutrition and the ability of neutrophil to generate reactive oxygen species was suggested. Furthermore, I evaluated the priming effect of lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNF-alpha) on whole blood CL. The CL responses stimulated with non-opsonized zymosan or P. aeruginosa were enhanced by pretreatment with TNF-alpha and LPS in healthy young adults. On the other hand, no significant priming effect was observed when blood from elderly patients were incubated with each primer. These findings suggest that the impairment in the generation of reactive oxygen species of the neutrophils and the decrease in reactivity to LPS and TNF-alpha that activate neutrophils at the site of infection and potentiate host defense against invading bacteria, may contribute to susceptibility to infection in the elderly.