TNF-alpha secretion, a biological marker of the inflammatory response to LPS, was not significantly different between U937-B27 and U937-control. No differences in gene expression between unstimulated U937-B27 and U937-control lines were detected. Both U937-control and U937-B27 exhibited a stereotypic response to LPS. Only one gene, OAS2, was differentially expressed by these cell lines, and this was confirmed by quantitative PCR