A competitive ELISA for the anti-intercellular adhesion molecule-1 (anti-ICAM-1) binding activity of monoclonal antibody R6.5 in serum.

A competitive ELISA was developed to measure serum concentrations of immunoreactive R6.5, a mouse IgG2a monoclonal antibody which binds to and inhibits the interactions of human intercellular adhesion molecule-1 with glycoproteins of the CD18 complex and with rhinoviruses. The assay design permitted quantitative measurement of the functional activity of the antibody in serum. The working range of the assay was from 2.15 to 215 ng ml-1, and intra-assay and inter-assay relative standard deviations averaged 13 and 20%, respectively. Serum caused interferences with the assay when spiked in vitro, but authentic serum samples obtained from intravenously dosed animals did not exhibit these interferences. Characteristics of the assay, as well as results of a pharmacokinetic study in rabbits, are presented.