Flow cytometry was used to analyze binding of rabbit antibodies to spleen leukocytes [9 (link)]. The cells in PBS containing 1% BSA were blocked with 10% (v/v) donkey serum (Southern Biotech, Birmingham, AL) before or after incubation with rabbit polyclonal anti-mutated peptide antibodies (1 × 107 cells/1.1 μg each Ab/100μL). Cell-bound rabbit Ig was detected with phycoerythrin-conjugated donkey anti-rabbit Ig (H + L) antibody (BioLegend, San Diego, CA). All the incubation steps were for 30 min in ice followed by three-time (3 min each) washings with PBS containing 1% BSA. The stained cells were fixed in 2% paraformaldehyde and following PBS washes, the samples were run on BD LSRII (BD Biosciences, San Jose, CA) flow cytometer equipped with BD FACSDiva™ version 8 software for data acquisition. The data were analyzed using FlowJo™ v10.1 software (FlowJo, LLC, Ashland, OR) following the required gating with the help of proper controls.