CD23hiCD58+ cells do not proliferate in the absence of EBV-exposed non-proliferating sub-populations of cells. Three days after exposure of CD3-depleted B cells to EBV, CD23hiCD58+ cells, representing 0.5% of the culture (A) were FACS-sorted. Post-sort analysis of CD23hiCD58+ cells is shown in B. Sorted CD23hiCD58+ cells were mixed with un-infected autologous primary B cells (as feeder cells) and re-introduced into culture at 0.5% of the total culture. Mock-sorted cells were also re-introduced into culture as control. Cells were harvested four days later and stained for CD23 (PE) and CD58 (FITC). Un-infected cells (C), EBV-exposed cells (D), mock-sorted but EBV-exposed cells (E), and sorted-CD23hiCD58+ cells mixed with un-infected B cells (F) after a total of 7 days in culture are shown. Percentages represent fraction of CD23hiCD58+ cells out of total.