Teleost IgD+IgM− B cells in gills and skin have a plasmablast profile, but functionally and phenotypically differ from IgM+IgD− B cells in these sites
Juan Germán Herranz-Jusdado, Esther Morel, Rocío Simón, Patricia Díaz‐Rosales, Carolina Tafalla
Abstract
Although most B cells in teleost systemic compartments co-express IgM and IgD on the surface, cells exclusively expressing either of the two Igs are common in fish mucosal tissues, providing us with a unique opportunity to further characterize IgD + IgM − B cells, an intriguing B cell subset. Hence, we compared the phenotype of IgD + IgM − cells to that of IgM + IgD − B cells in rainbow trout gills and skin, also establishing the response of these subsets to immune stimulation. The transcriptional profile and secreting capacity of IgD + IgM − B cells corresponded to that of cells that have started a differentiation program toward plasmablasts, similarly to IgM + IgD − B cells. Yet, IgM + IgD − B cells retained high levels of surface MHC II and antigen-processing abilities, while these were much lower in IgD + IgM − cells, suggesting important differences in their antigen-presenting capacities. Our findings contribute to a deeper understanding of the enigmatic role of IgD in mucosal surfaces.