Zebrafish B cells are marginally phagocytic. (A) Adult zebrafish were injected intraperitoneally with fluorescent E coli (pHrodo). After several hours, PEX was collected and analyzed by flow cytometry. Left: FSC/SSC profile of cells from the PEX. Right: Total percentage of pHrodo⁺ cells in each cell population at various time points. (B) IgM⁺ B cells and granulocytes were purified by flow cytometric sorting from adult IgM1:eGFP fish and cultured in vitro with pHrodo. Flow cytometric profiles of B cells and granulocytes after 4 hours of culture are shown. These results are representative of at least 3 independent experiments.