Novel method for detection of ex vivo tumor necrosis factor alpha production by monocytes

Tumor necrosis factor alpha (TNF-alpha) has come into recent focus as a proinflammatory cytokine derived from monocytes/macrophages. We developed a novel system (the SEK-5001 system) for measurement of ex vivo production of TNF-alpha stimulated by lipopolysaccharide (LPS) as a marker of immune function. In the present study, we evaluated the performance of this system as a diagnostic tool. Furthermore, we compared TNF-alpha levels with data from other immune function tests, including lymphocyte blast formation test and differential leukocyte counts. Incubation of whole blood with a stimulation of low-dose LPS (100 EU/mL blood) for 4 hr at 37 degrees C gave acceptable results. After incubation, plasma TNF-alpha levels were determined by enzyme-linked immunosorbent assay (ELISA). The specificity, reproducibility, and recovery of the SEK-5001 system were excellent. No correlation between TNF-alpha levels and total leukocyte counts was found. Lymphocyte blast formation test and monocyte counts, however, were correlated with TNF-alpha levels in blood from patients with hematological malignancy and aplastic anemia before treatment. This assay system may potentially be clinically applicable to assess in vivo immune function.