Figure 1. BCR-mediated internalization of Salmonella by primary human B cells.
(A) Immunocryoelectron micrograph of primary human B cells that had phagocytosed anti-BCR coated Salmonella. Gold particles indicate staining for CD63, black asterisks mark bacteria, N marks the nucleus and PM the plasma membrane. (B) Primary B cells were either or not pre-incubated with F(ab)2 fragments of the anti-IgM antibody before incubation with live anti-IgM coated GFP-expressing Salmonella. After extensive washing, cells were fixed and analyzed by FACS indicating a strong reduction in GFP-Salmonella following competition with F(ab)2 for BCR interactions. Shown is a representative plot of 5 donors tested.