Practice question

Microtiter polystyrene wells possess high protein-binding capacity and retain unoccupied hydrophobic surfaces after antigen coating. Without intervention, primary or secondary antibodies could adsorb nonspecifically to these empty sites, elevating background and causing false positivity. Blocking agents such as bovine serum albumin, casein or skim milk proteins saturate residual surfaces, forming an inert layer that prevents random adsorption while preserving specific immune complexes. This step improves signal-to-noise ratio, enhances assay precision and ensures color development reflects true antigen-antibody interaction rather than plastic binding artifacts.