Sandwich ELISA analysis of IL-4 matched pair antibodies Elisa assay was performed by coating wells of a 96-well plate with 50 µl per well of capture antibody HA721230 [PS00-67] diluted in carbonate/bicarbonate buffer, at a concentration of 1 µg/mL overnight at 4℃. Wells of the plate were washed, blocked with 150 µl 1%BSA/PBST blocking buffer, and incubated with serial diluted Recombinant IL-4 protein starting from 2000 pg/ml to 30.5 pg/ml for 1 hour at 37℃. The plate was washed and incubated with 50 µl per well of detect antibody HA721368 [PS00-66] (Biotin, 1:4000) for 1 hour at 37℃. Then the plate was washed and incubated with 50 µl per well of Streptavidin-HRP for 0.5 hour at 37℃. Detection was performed using an Ultra TMB Substrate for 10 minutes at room temperature in the dark. The reaction was stopped with sulfuric acid and absorbances were read on a spectrophotometer at 450 nm. Capture/detect antibodies, Recombinant IL-4 protein, Streptavidin-HRP are diluted in 1% BSA/PBST.