Morphological characterization of mouse B-1 cells

At least three B cell subsets, B-1a, B-1b and B-2 are present circulating peripherally in the mouse. In these animals, B-1 cells constitute a minor fraction of B cells in spleen and are absent in lymph nodes although they represent the main B cell population in peritoneal and pleural cavities. Currently these cells are identified by a surface phenotypic repertoire; they express Mac-1, IgM(high), and B220(low). B-1a cells express CD5. The aim of this work emerged from the fact that the morphology of B-1 cells is not fully characterized. Here we identified B-1 cells using colloidal gold immunocytochemical assays and purified B-1 cells from supernatants of adherent peritoneal cell cultures by a magnetic bead technique. These techniques lead us to demonstrate that, in mice, either B-1a or B-1b cells have a unique morphology distinct from that of B-2 cells.