Competitive receptor-binding assay

CHO-PRLR cells were cultured in serum-free F-12K medium containing 1% bovine serum albumin for 12 h. The cells were subsequently washed and incubated with 125I-PRL (5,000 CPM/well) together with increasing concentrations of unlabelled PRL and Mab2s or isotype-matched control antibody for 2 h. After the incubation, the cells were washed and detached from the plate. The cells were then counted in a gamma counter. The non-specific binding was determined in the presence of 5 μg unlabelled PRL.