We often have problems in immunostaining the trachea and bronchi
in the sheep, with nonspecific binding of rabbit antibody onto mucus and 
cartilage.  I suspect this is charge-related.  Does anyone have 
experience with a blocking step that will reduce this problem,
perhaps by blocking the strong anions on mucus and cartilage?

Thanks,

Hal Hawkins
UTMB, Galveston, Texas