ELISA of anti-CD27 antibody on CD27-Fc fusion protein- with a CD70 (CD27-L) competition assay. Binding curves of the r chimeric version of the anti-CD27 (Interleukin-2 receptor subunit alpha) antibody RM27-3E5 (24-558; red line) and isotype control (anti-Fluorescein antibody 3.0 4-4-20 (enhanced); blue line) to an ELISA plate coated with CD27-Fc fusion protein (Pr00160-1.9) at a concentration of 5 ug/ml. A 3-fold serial dilution from 10 mg/mL to 0.17 ng/ml of 24-558 was used. CD70 (CD27-L) is the ligand for CD27. CD70 Fc-fusion protein (Pr00161-1.28) was added to a 10mg/mL solution of 24-558 starting at 10mg/mL- and then at 3-fold dilutions down to 0.17ng/mL (red line). A negative control assay using 4-1BB Fc-fusion protein (Pr00233-1.9) was also performed (yellow line). Inhibition of the binding of 24-558 to Pr00160-1.9 (CD27) by Pr00161-1.28 (CD70) may be observed between 10-000 ng/mL and 123 ng/mL of Pr00161-23.0- whereas Pr00233-1.9 (4-1BB) does not inhibit 24-558 binding. For signal detection- a 1:4000 dilution of HRP-lnti-human IgG antibody was used.