Requirement for CD21 for EBV-2 infection of Jurkat T cells. (A) CD21 (clone HB5) expression on unstained Jurkat (light gray), unstained Raji (dark gray), Jurkat (green), and Raji (blue) cells. (B) Viral load 24 h following infection of Jurkat cells with EBV-2 virus (5 genome copies/cell). Uninfected cells (mock) were a negative control. Data are presented as log(copies/microgram). (C) Neutralization assay using Jurkat cells and infecting with EBV-2. Viral loads were normalized to the uninhibited EBV-2 infection of Jurkat cells. Virus was incubated with 10 μg of anti-gp350 antibody (clone 72A1) (P = 0.0022), or the cells were incubated with 10 μg of anti-CD21 antibody (clone 171) (P = 0.0411) (5 genome copies/cell). (D) CD21 expression of Jurkat CAS9 cells and CD21 knockout cells. (E) Pre- and postsorting analysis of CD21 knockout cells. (F) EBV viral load at 1 dpi and 3 dpi following infection of Jurkat, Jurkat Cas9, and the three CD21 knockout cell lines with EBV-2 virus (10 genome copies/cell). ND, not detected.