FIG. 6.

Effect of purified Stx1 on expression of activation markers by bovine PBMC in vitro. Cells were incubated with purified Stx1 (200 CD₅₀/ml; quantified on Vero cells as described in Materials and Methods) at 37°C. The culture medium was free of mitogens (A) or was supplemented with 5 μg of PHA-P/ml (B) or 25 μg of LPS/ml (C). Observed effects were assigned to Stx1 by comparison of results obtained in the absence (open circles) or presence (filled circles) of 1.5 μg of the monoclonal anti-StxB1 antibody 13C4/ml. Lymphocyte subpopulations were identified by immunophenotyping at the time points indicated and quantified by flow cytometry acquiring 5,000 events. Data analysis was performed by using the software of the instrument to calculate the percentage of viable (PI-negative), immunolabeled events belonging to the blast cell population.