Elderly individuals have an increased susceptibility to infections. To evaluate one of the possible causes of increased susceptibility to infections in the elderly, peripheral neutrophil and monocyte counts, neutrophil and monocyte chemiluminescence (ChL), macrophage precursor test and production of colony-stimulating factor (CSF) of peripheral mononuclear cells (PMNCs) were examined. The neutrophil and monocyte counts in the peripheral blood were not different between the elderly (≧70 years old) and the younger (<70years old) groups. In the neutrophil ChL assay, the base lines, peak levels and peak times were not different between the elderly and the younger groups. In the monocyte ChL assay, the peak level in the elderly group was significantly lower than that in the younger group (p<0.05). The values in a macrophage precursor test in the eldely group were signicantly lower than those in the younger group (P<0.05). CSF production of PMNCs in the eldely was significantly lower than that in the younger group(P<0.05). These findings indicated that the impaired intracel-lular bactericidal activity and maturation ability of monocytes and impaired CSF production of PMNCs were possible causes of increased susceptibility to infections in the elderly.
macrophage precursor test