THE EFFECT OF AGE AND DIABETES-MELLITUS ON SERUM LEVELS OF LYMPHOTOXIN

To determine whether chronic hyperglycemia or aging is associated with increased serum levels of lymphotoxin, sera were obtained from 29 insulin-treated diabetic patients and 50 healthy subjects ranging in age from 22 to 97 years old. An ELISA system specific for human lymphotoxin was developed with the lower limit of sensitivity at 76 pg/ml and interassay coefficient of variation of <7%. Serum levels of tumor necrosis factor (TNF) alpha, interleukin 1 (IL-1) alpha and beta were measured with previously described ELISA system. The WEHI 164 cytotoxicity assay was used to measure bioassayable TNF-like activity. Of the 29 diabetic patients, seven had detectable serum immunoreactive lymphotoxin levels and three had bioassayable serum levels of TNF-like activity. In contrast, only one healthy subject had detectable serum lymphotoxin levels (p<0.01). Of the 22 diabetic patients who did not have detectable levels of lymphotoxin, 5 had detectable TNF-alpha, 4 had detectable IL-1-alpha, and none had detectable IL-1-beta levels. Thus, there was no correlation between serum lymphotoxin level and serum levels of TNF-alpha, IL-1-alpha or IL-1-beta. Aging is not associated with altered serum levels of lymphotoxin while 24% of diabetic patients have increased serum levels of immunoreactive lymphotoxin.