Immunologic function in the elderly after injury--the neutrophil and innate immunity

Aging is associated with a decline in immune function. This may contribute to decreased ability of an elderly patient to mount an appropriate innate inflammatory response when injured. This study examined elderly trauma patients to determine whether there was a difference in neutrophil response to injury when compared with controls.

This prospective, observational, cohort study compared neutrophil function in 24 injured elderly (older than 65 years) patients admitted to our trauma center to control groups of noninjured individuals (11 elderly and 17 young). Blood samples were also taken from the injured elderly group within 48 hours of trauma and subsequently at two periods during their hospital stay. A single blood sample was obtained from the noninjured control groups. Neutrophils were analyzed for CD18 expression, stimulated oxidative burst, apoptosis, and IL-10. Results were compared using one-way analysis of variance (alpha 0.05). This study was approved by the Institutional Review Board.

Twenty-four injured elderly subjects were enrolled: mean injury severity score 15.3, average age 74.6 years, 92% survival, 100% blunt trauma. CD18 levels in the elderly injured subjects for all three time periods were significantly higher than both control groups. When evaluated between controls, CD18 for the noninjured elderly (NIE) was also significantly higher than the noninjured young (NIY). The neutrophil stimulated oxidative burst in the injured elderly subjects at time periods 1, 2, and 3 was not significantly different from the NIY controls. However, the injured elderly had a significantly higher oxidative burst at time period 3 than the NIE controls. Apoptosis in the injured elderly subjects was significantly lower in all three time periods than the NIY. There was no difference in apoptosis between the injured elderly subjects when compared with the NIE controls. There was no significant difference in IL-10 expression among groups.

Injury results in differences in innate immune function in the elderly when compared with controls. The clinical significance of this is uncertain and warrants further investigation.