Radioimmunoassay for leukotriene B4.

A rabbit immunized with leukotriene B(4) [LTB(4); (5S,12R)-6, 14-cis-8, 10-trans-icosatetraenoic acid] coupled to bovine serum albumin via the 12-oxy function of the lipid produced antibodies having an average association constant (K(a)) for [14,15-(3)H]LTB(4) of 3.2 x 10(9) M(-1) at 37 degrees C and in a concentration of 0.37 mug/ml of the immune plasma. When 10 mul of anti-LTB(4) and 3.9 nCi of [14,15-(3)H]LTB(4) (28 Ci/mmol; 1 Ci = 3.7 x 10(10) becquerels) were incubated in a volume of 250 mul, 50% inhibition of radioligand binding was achieved with 0.31 ng of LTB(4) and with 1.95 ng of (5S,12S)-6-trans-8-cis-LTB(4). The sulfidopeptide leukotrienes, LTC(4) and LTD(4), displaced the radioligand from this antibody with less than 1/100th the activity of LTB(4), and the diastereoisomers of 6-trans-LTB(4), 5-L-hydroxy-6-trans-8,11,14-cis-icosatetraenoic acid (5-HETE), and three prostaglandins were minimally effective. The specificity of this radioimmunoassay was further shown by assessment of the immunoreactive products generated from calcium ionophore (A23187)-activated rat serosal mast cells and human neutrophils after reversed-phase HPLC. Resolution of the supernatants from each cell type yielded a single immunoreactive peak that coeluted with synthetic LTB(4) and quantitatively correlated with the physical measurement by integrated A(269) in that peak; UV-absorbing peaks eluting at other retention times were not immunoreactive. The immunoreactive LTB(4) generated averaged 4.6 ng per 10(6) rat mast cells and resolution of the supernatants by reversed-phase HPLC without a prior extraction step gave a recovery of 54%, validating the direct applicability of this sensitive and specific assay for LTB(4), a highly potent chemotactic factor, to unfractionated biologic fluids.