Flow cytometry analysis and cell sorting. Analytical flow cytometry analysis was performed on whole blood after lysis of erythrocytes and fixing in 2% PFA. All live cell sorting and single cell sorting was performed on purified PBMCs using either a FACSVantage or ARIAII cell sorter system. All of the following antibodies for both analytical and cell sorting cytometry were purchased from BD, except anti-CD27, which was purchased from eBioscience: anti-CD3-PECy7 or PerCP, anti-CD20-PECy7 or PerCP, anti-CD38-PE, anti-CD27-APC, and anti-CD19-FITC. ASCs were gated and isolated as CD19 + CD3  CD20 lo/ CD27 high CD38 high cells. Flow cytometry data were analyzed using FlowJo software.