Table 3. Effect of different blocking reagents on background reduction of CK1δ immunostained frozen sections.

blocking solution	specific against	background reduction
Levamisole	endogenous alkaline phosphatase	+ +
peroxidase-blocking reagens (DAKO)	endogenous peroxidase	+ +
Uni-Block (BioGenex)	endogenous biotin	+ + +
Avidin/Biotin Blocking Kit (Zymed)		+
blocking solution	unspecific against	background reduction
Aurion BSA-c, (Biotrend)	hydrophobic and electrostatic interactions	−
Power Block, Casein (BioGenex)		−
anti- IgG F(ab′)2-fragment		background reduction
• Anti-Rabbit IgG F(ab′)2 biotinylated (DAKO)		−

Frozen tissue sections were immunostained for CK1δ in the presence and absence of the indicated blocking reagens. − no effect of the blocking reagens; + low background reduction; ++ medium background reduction; +++ strong background reduction.