FIG. 4.

Receptor-binding properties of HA-tagged SUs. MDTF or MDTF-Pit cells were incubated with 500 μl of conditioned medium containing the SUs indicated (upper right corner) as described in Materials and Methods. Bound SUs were detected by staining with a monoclonal antibody directed against the HA epitope. In all cases the x axis is fluorescence intensity (log scale) and the y axis is cell number. Mock samples (open profiles), cells incubated in standard media and stained with the same antibody. Pit receptor and SU abbreviations (upper right corner) are as described in the legends to Fig. 1 and 3.