A capture assay to analyse immunoglobulin secretion at the single-cell level

Several secretion capture assays have been developed to measure a secreted protein of interest, using paired monoclonal antibodies of different specificities that bind simultaneously to a cell surface antigen and to the secreted protein of interest. Here we have developed a novel method to measure antibody secretion on B cells, which, by capitalising on the bivalent nature of an antibody molecule, utilises an anti-immunoglobulin (Ig) antibody to bind on one side to the membrane-bound Ig (in the B cell receptor), and then capture any secreted Ig with the second binding site. Binding of the secreted cargo is then detected through a second application of anti-Ig, this time fluorophore-labelled. We demonstrate that this can effectively measure single cell Ig secretion in a population of B cells undergoing differentiation to plasma cells. This offers a reliable and accessible tool for quantifying antibody secretion dynamics at the single-cell level with potential applications in immunological studies, antibody discovery and functional profiling of B cell responses.