REDUCED NEUTROPHIL PHAGOCYTIC INDEX IN THE ELDERLY: POTENTIAL ROLE IN INCREASED SUSCEPTIBILITY TO POST-TRAUMATIC INFECTION

Abstract

To determine the effect of normal human ageing on neutrophil function and to assess the contribution that any decline may play in the increased susceptibility of elderly patients to bacterial infections following minor trauma. Furthermore, to determine any contribution, of trauma, to further neutrophil decline in these elderly patients.

Phagocytic index, CD16 (FcγRIIIB) and CD11b (CR3) expression were determined in neutrophils isolated from the peripheral blood of 15 healthy young (average age 26. 5 yrs, range 23–35 yrs; 8 male, 7 female) and elderly (average age 72. 9 yrs, range 65–71 yrs; 8 male, 7 female) volunteers. CD11b levels were unaltered, but phagocytic index and CD16 expression were both significantly reduced (p< 0. 05 and p< 0. 001 respectively) in the elderly group. CD16 levels were monitored in a large volunteer group and were found to correlate with phagocytic index. To determine whether trauma produces additional compromise to neutrophil function in the elderly, peripheral blood neutrophils from individuals (average age 82. 5 yrs, range 65–96 yrs; 7 male, 21 female) during neutrophilia, post-trauma, due to fracture of the femur, were analysed as described above. Patients with chronic inflammatory disease, diabetes or kidney disease, or who were receiving steroid medication, were excluded. The data showed that neutrophil CD16 expression was significantly reduced in the elderly group (p< 0. 05), furthermore following fracture of the neck of femur superoxide generation is significantly reduced. Patient follow up revealed that 17 (60. 8 %) of these patients subsequently acquired bacterial infections (including wound), within 4 weeks of trauma.

Normal human ageing was accompanied by a decline in neutrophil phagocytic ability and this may be in part due to reduced levels of the Fcγ receptor CD16. The reduced neutrophil CD16 expression accompanied by reduced superoxide generation in the elderly trauma patients may significantly undermine their ability to combat bacterial infections and contribute to increased incidence of post-traumatic infections in the elderly.