If nothing specific comes to mind with respect to the CD surface
antigens and you do not want to discriminate on the bases of
elastical light scatter, an optional staining would be one that
reacts with:
MPO (specific for neutrophils)
EPO (specific for eosinophils)
IgE (specific for basophils)
Robbert van Leeuwen
Applied Optics / Flow Cytometry Group
University of Twente
The Netherlands