Binding characteristics required for reversible Fab-multimer staining.

<p>FACS analysis of anti-CD4 Fab-multimer staining with different anti-CD4 Fab mutants with decreasing affinities. PBMCs were stained with the respective PE-labeled anti-CD4 Fab-multimers and analyzed either before (second column) or after treatment with D-biotin (third column). Remaining Fab-monomers were then detected after subsequent washing steps using (uncomplexed) PE-labeled <i>Strep</i>-Tactin (fourth column). Secondary Fab-multimer staining of reversibly stained cells served as control (right column). Alternatively, cells were incubated with monomeric Fab-fragments, washed and subsequently analyzed after staining with <i>Strep</i>-Tactin (left-most column). Live CD3⁺ T cells are shown. Numbers in the dot plots indicate the percentage of cells within gates.