An amplified ELISA for human tumour necrosis factor alpha.

An immunoassay for tumour necrosis factor alpha (TNF-alpha) is described using a sandwich system which employs a mouse monoclonal as the capture antibody and a polyclonal rabbit anti-TNF-alpha as the detection antibody. The assay utilises a novel enzyme cycling system to amplify the colourimetric signal generated by alkaline phosphatase in the enzyme immunoassay. The assay sensitivity is increased by the use of the AMPAK system. The detection limit of the assay is in the order of 1 pg/ml which is many times greater than is possible with conventional methods of measurement. The advantages of the enzyme-amplified method will be particularly useful in the quantitative determination of low levels of TNF-alpha in body fluids. This assay system was used to measure peripheral serum TNF levels in a group of women with non-malignant gynaecological conditions, the mean TNF-alpha concentration in these subjects was 10 pg/ml.