Hi Tibor,
You need to use some type of heat induced antigen retrieval for
calretinin. I use Zymed's polyclonal anti-calretinin at a dilution of
1:50 and pretreat my slides in a microwave pressure cooker in citrate
buffer pH 6.0 for 15 min.
Let cool for 20 to 30 minutes and continue with the procedure. I use
biotin/streptavidin detection system. Good luck!

Katri 

Katri Tuomala
Anatomic Pathology
St.Joseph's Hospital
Hamilton, Ontario, Canada