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. Copyright 2002 Wiley-Liss, Inc.