Figure 4.

Down-regulation of syk in CD34-derived basophils cultured in the presence of a chronic aggregating stimulus. CD34⁺ progenitors were cultured in the presence of 500 ng/ml IgE (2.6 nM) or IgE plus anti-IgE (aIgE) at a 10:1 or 2:1 molar ratio (42 ng/ml and 210 ng/ml, respectively) for the entire 3-week culture. Expression of FcεRI and syk in the treated cells was compared with cells grown without any IgE or aggregating stimulus (control) at Day 21 of cultures. (A) FcεRI expression. (B) Representative flow cytometry experiment in which syk levels (solid) are measured relative to the isotype control (outline). (C) Percentage of cells in the high versus low syk populations observed for cells grown in the presence of a chronic aggregating stimulus (n=4 for 10:1 ratio; n=3 for 2:1 ratio). The light bars represent cells that fall in the low syk expression analysis “gate” and the dark bars, cells in the high syk expression gate. (D) Average syk levels (MFI) in the high and low syk populations. The light bars represent the mean syk expression levels in cells “gated” for low syk expression and dark bars, mean expression levels for cells gated for high expression.