biostudies-literatureHeo MEuropean Research Council614https://www.ebi.ac.uk/biostudies/studies/S-EPMC7589517biostudies-literatureUnknown3(1)Antibodies with antibacterial activity need to bind to the bacterial surface with affinity, specificity, and sufficient density to induce efficient elimination. To characterize the anti-bacterial antibody repertoire, we developed an in-droplet bioassay with single-antibody resolution. The assay not only allowed us to identify whether the secreted antibodies recognized a bacterial surface antigen, but also to estimate the apparent dissociation constant (K_{D app}) of the interaction and the density of the recognized epitope on the bacteria. Herein, we found substantial differences within the K_{D app}/epitope density profiles in mice immunized with various species of heat-killed bacteria. The experiments further revealed a high cross-reactivity of the secreted IgG repertoireCommunications biologyDeep phenotypic characterization of immunization-induced antibacterial IgG repertoires in mice using a single-antibody bioassay.PMC758951761605080336Bibette JBruhns PCastrillon CChenon GBaudry JHeo MGriffiths ADEyer KfalseDeep phenotypic characterization of immunization-induced antibacterial IgG repertoires in mice using a single-antibody bioassay.Antibodies with antibacterial activity need to bind to the bacterial surface with affinity, specificity, and sufficient density to induce efficient elimination. To characterize the anti-bacterial antibody repertoire, we developed an in-droplet bioassay with single-antibody resolution. The assay not only allowed us to identify whether the secreted antibodies recognized a bacterial surface antigen, but also to estimate the apparent dissociation constant (K_{D app}) of the interaction and the density of the recognized epitope on the bacteria. Herein, we found substantial differences within the K_{D app}/epitope density profiles in mice immunized with various species of heat-killed bacteria. The experiments further revealed a high cross-reactivity of the secreted IgG repertoire2020-01-01T00:00:00Z2020 Oct2026-07-16T02:33:27.059Z2025-05-31T22:43:03.46ZS-EPMC75895173310652610.1038/s42003-020-01296-3