Human plasma/plasmablast cell (PC) isolation by fluorescence-activated cell sorting (FACS) using ER-tracker and anti-human IgG. (A) A representative FACS graph of cells prepared from the lymph nodes of cancer patients. Cells were stained with anti-human IgG Dylight 488 and ER-tracker, and the IgGlow endoplasmic reticulum (ER)high cells were further analyzed for CD38-APC versus CD20-PE surface expression using FACS. The forward-versus-side-scatter (FSC vs SSC) with gate R1 represents lymphocytes. PCs are defined herein as CD38high CD20low cells. A representative FACS graph of three separate experiments is shown. The relative number of cells in each region is given as a mean percentage of three separate experiments. (B) R1-gated and R2-gated cells stained intracellularly with anti-human IgG Dylight 488 (green). Nuclei are stained with 4',6-diamidino-2-phenylindole (DAPI; blue). The numbers indicate the percentages of cells with intense cytoplasmic IgG. (C) Representative agarose gel electrophoresis of cognate pairs of V genes amplified from single-cell-sorted R3-gated cells. (D) Polymerase chain reaction (PCR) success ratio for V genes from single-cell-sorted R3-gated cells from lymph nodes of patients with colon and gallbladder cancers.