Human interleukin 2. Detection at the picomolar level by sandwich enzyme immunoassay

Human interleukin 2 was detected at the pM level by a simple sequential sandwich enzyme immunoassay. The lymphokine to be assayed was first extracted from supernatants of mitogen-activated Jurkat leukemic T cells or peripheral blood lymphocytes using anti-recombinant interleukin 2 rabbit IgG insolubilized onto polystyrene microtiter plates and was revealed by an anti-interleukin 2 Fab' fragment conjugated to peroxidase. The whole method could be performed within 8 h and allowed the measurement of interleukin 2 irrespective of its degree of glycosylation. Among the currently used mitogens, only ConA at a concentration above 10 micrograms/ml interfered with the assay. The method was carefully compared to the reference bioassay and was found to be only 3-5 times less sensitive.