[Histonet] Immunofluorescence staining artefact?

[P. Krawczyk]

Hallo, 
I'm performing a double fluorescent staining (Cy3 + FITC) of adherent cells
fixed with 2%paraformaldehyde. In my stained cells, apart of the typical
staining pattern i see small, very bright Cy3 dots, moving fast with a kind
of Brownian motion. Their size is in the microscope resolution area (viewed
with 100x magn.) Nothing can be spotted with the phase contract, so it's not
bacteria. I tried filtering, centrifuging, nothing... It seems, that a long
washing reduces this artefact. Are these Cy3 clumps? 
Anyone knows what it is and how to get rid of it?
Any help appreciated,
Regards, 
P. Krawczyk
 
_____________________________
P. M. Krawczyk
Dept. of Cell Biology and Histology
Academic Medical Centre
University of Amsterdam
Meibergdreef 15, room M3-107
1105 AZ, Amsterdam
The Netherlands
 
Email:  P.Krawczyk <@t> amc.uva.nl
Tel:     +31 20 5668746
Fax:    +31 20 6974156