Figure 3

Optimization of ELISA assay parameters. A. Increasing concentrations of monoclonal antibodies RA, RC and RD were used in the ELISA assay with a constant amount of PA103 culture supernatant serving as bound antigen. B. PA103 and PA103ΔU culture supernatants were mixed in the proportions indicated to vary the amount of ExoU present in each sample while holding other secreted antigens constant. The mixed supernatants were diluted with carbonate buffer as indicated, then assayed by ELISA using antibodies UA and UB. Values represent the average of the signal obtained with the two antibodies.