FIG 2.

Preincubation with anti-B19V antibodies strongly stimulates B19V uptake into the monocytic cell line U937 and endothelial cells. (A to F) Different cell lines and primary endothelial cells, as indicated, were either mock infected or infected with B19V at an MOI of 1,000 genomic particles per cell. After 6 h of incubation at 37°C, genomic-DNA preparations were assayed for the number of B19V genomes by quantitative PCR. B19V DNA is presented on a logarithmic scale as genomic copies per cell initially infected. For the bars marked “+ control-IgG” or “+ α-B19V-IgG,” the B19V particles were preincubated prior to infection with purified IgG preparations from selected human sera with anti-B19V titers (index numbers) of <0.9 (control) or 8.0 (α-B19V), respectively, for 1 h at 37°C. The final concentrations of immunoglobulins during infection were 400 μg/ml. (E and F) In addition to the anti-B19V antibody-positive IgG preparation from serum 1 used in panels A to D (index number, 8.0), two further preparations with index numbers of 6.0 (serum 2) and 5.2 (serum 3) were used. The data are presented as means plus standard deviations.