Optimum ag ab concentration is required to form visible immunological reactioñs. As explaiñed in lattice theory, Marrack"s hypothesis.

Typically, ag binding sites on ab would either be folded or submerged.

Dominique Blanchard , the antibody may start to aggregate at high concentrations, decreasing activity. This behavior is specific to each different antibody, since they will have different biophysical profiles.

Could you give us more details about your assay format? There are several mechanisms, which have to be taken into consideration.

Thanks all for your answers. Michael G. Weller the question relates to flow cytometry assay. Andre A. Teixeira Indeed aggregation was an option but it is unlikely since we are far bellow of the concentration of our stock solution. However, I cannot exclude this option. Gayathri Devaraja

I also should add. That it has been observed with both bivalent (full mAb) and monovalent (mAb fragment ).