Cytokine production and aging: overproduction of IL-8 in elderly males in response to lipopolysaccharide

Abstract

Interleukin-8 (IL-8) is a chemoattractant cytokine for polymorphonuclear neutrophils, and is found at the site of inflammation and infection. The levels of IL-8 from an elderly (ages 65-79) and young (ages 20-27) population were compared. Secretion of IL-8 was measured in monocyte conditioned medium (MCM), under both a spontaneous condition and with stimulation with detoxified LPS (10 mg/ml). Spontaneous production of IL-8 in the elderly group (39.4 +/- 8.3 ng/ml, n = 16) was found to be significantly lower than the control group (66.4 +/- 5.0 ng/ml, n = 17), P < 0.01. A sex difference was observed within the elderly population, with the male elderly producing 8.8 +/- 2.1 ng/ml of IL-8 and the elderly females producing levels of 57.8 +/- 9.1 ng/ml. There was a good correlation between IL-8 and IL-1 production in the elderly but differences between the elderly and young production of IL-1 did not reach statistical significance. IL-8 and TNF production did not correlate. Upon stimulation with the LPS, the male elderly levels increased eightfold (70.1 +/- 11.8 ng/ml) and was significantly different from the young male level, P < 0.01, while the female elderly showed no change with stimulation. No sex difference was observed in the control population. These results indicate that the spontaneous secretion of IL-8 in elderly males is lower than that of both elderly females and the young control group. However, upon stimulation with LPS, the elderly males are capable of an overproduction of IL-8 when compared to the young group and the elderly females. This overproduction may be the result of an in vivo priming in this healthy elderly group. The female elderly followed a pattern similar to the young group, showing no change upon stimulation with the detoxified LPS. Sex differences related to the immune system have been noted in the past with females having a more active immune system, and these results may be related to this difference.