Blast transformation and outgrowth of human peripheral blood B cells after stimulation with CSB. Control PBMC (1 × 106/mL) or PBMC stimulated with either CSB, HA, PHA, or CSB in combination with rTGFβ1 (1 ng/mL) were cultured for 6 days and then immunostained with phycoerythrin-conjugated CD19 MoAb and analyzed on a FACScan. Two-dimensional plots were generated in which CD19-positivity was plotted on the x-axis and side scatter (as a reflection of cell size) was plotted on the y-axis. In (A), the percentage of CD19+ cells showing blast transformation (as reflected in a size exceeding a threshold value established by control unstimulated cells) has been calculated. In (B), the overall percentage of CD19+ cells detected in these plots is shown. Nonspecific binding was controlled by using appropriate isotype-matched antibodies and was the same for all cultures.
