AN ELISA FOR THE MEASUREMENT OF HUMAN LEUKEMIA INHIBITORY FACTOR IN BIOLOGICAL-FLUIDS AND CULTURE SUPERNATANTS

A new monoclonal antibody-based ELISA for leukaemia inhibitory factor/ human interleukin for DA cells (LIF/HILDA) measurements is described. The sensitivity (56 pg/ml after 4 h incubation, 14 pg/ml after 24 h in cubation), precision (intra-assays < 5%), reproducibility (interassay < 10%), and accuracy (recoveries, ranging between 98 and 119%, in seve ral fluids) of the assay, plus its exellent performance in dilution te sts, and the lack of interference when in the presence of possible cro ss-reactive substances guarantee accurate cytokine measurement in biol ogical fluids such as serum, plasma, synovial fluid, follicular fluid, urine and culture supernatants. Using the assay, LIF/HILDA was measur able in supernatants after in vitro whole blood stimulation with phyto hemagglutinin (PHA), OKT3, and phorbol myristate acetate (PMA) but not with lipopolysaccharide (LPS) or Ca ionophore. LIF/HILDA production w as not measurable until after 24 h of culture, when cytokine levels we re seen to increase linearly in the supernatant to reach values of up to 40 ng/ml after 96 h of culture. Finally, a good correlation was fou nd (r = 0.96; p < 0.0001; y = 23.1x + 233) between the LIF/HILDA value s obtained using the ELISA and DA-1a bioassay.