Increased Soluble Tumor Necrosis Factor Receptor Levels in the Serum of Elderly People

Abstract

Background: Soluble (s) forms of tumor necrosis factor (TNF) receptors are the only natural molecules known to interfere with TNF activity by competing for TNF binding with receptors on target cells. In a variety of pathologic situations, the concentrations of sTNF receptors (R) increase. Objective: To discuss possible causes of increased risks for infectious disease and cancer seen in the elderly. Methods: The participants were healthy subjects (n = 48) of three age groups (young, middle-aged, and elderly). Patients with senile dementia of Alzheimer type (n = 25) were also studied. For detection of cytokines, interleukin (IL) 1α, IL-1β, IL-6, macrophage colony-stimulating factor (M-CSF), granulocyte colony-stimulating factor, and TNF-α were measured in serum by enzyme-linked immunosorbent assays, as were soluble (s) IL-1 receptor antagonist (IL-1ra), sIL-6R, p55sTNF-R, and p75sTNF-R. Results: IL-1α, IL-1β, IL-6, and TNF-α were not detected, and sIL-6R and IL-1ra concentrations were not significantly different between the three age groups. However, sTNF-R and M-CSF were increased in sera from the elderly, both healthy and demented. A significant correlation was seen between sTNF-R and M-CSF concentrations. Conclusions: Increased sTNF-R levels may oppose the physiologic and protective effects of TNF by interference with its receptor binding. This interaction may contribute to the susceptibility of the elderly to infectious and neoplastic diseases.