Figure 4.

Differential binding of CTLA4Fcε and IgE to RPMI‐8866 cells. (a) Left and middle column histogram series show representative flow cytometric analyses of RPMI‐8866 cells incubated with six different concentrations (from 1·4 to 45 nm) of IgE or CTLA4Fcε, respectively, and subsequently stained with phycoerythrin‐labelled anti‐human IgE (anti‐IgE/PE). The right column histogram series contains data from a similar experience in which RPMI‐8866 cells were pretreated with 200 nm CTLA4‐Ig (to block CD80 and CD86 sites), incubated with CTLA4Fcε, and finally stained with anti‐IgE/PE. Mean fluorescence intensity (MFI) values of the control condition (no protein) and of each protein concentration assayed are included for comparisons (inset numbers shown at the right upper corner of each histogram). Also included for comparisons are values that represent, for each protein concentration assayed, the number of times the CTLA4Fcε‐related MFI was higher than the IgE‐related MFI (inset underlined numbers shown below MFI values in the middle and right column histogram series) The results shown come from a single experiment and are representative of seven independent experiments, each performed in duplicate. (b) RPMI‐8866 cells were stained with fluorescent anti‐human CD80 and anti‐human CD86 in the presence of two different concentrations of CTLA4‐Ig and analysed by flow cytometry. The results shown come from a single experiment and are representative of at least two independent experiments, each performed in duplicate.