immunofluorescence background

[Danny Altshuler]

Hi, everybody
I'm doing some fluorescence using the biotynilated 
antibodies/streptavidin Texas Red. I'm using 4% parafolmadehyde and 0,5% 
Triton for the fixation /permeabilization steps.
My problem is in the background. I started using BSA 3% whitout luck and 
then switch to 5% calf serum. The background was reduced but is still there.
Please any suggestion or good protocols are wellcome
BTW these are NIH 3T3 cell lines
Thanks
Danny