Dear All,

Before available antibodies to mast cell enzymes I used a method I got 
from Lung T. Yam using the enzyme substrate naphthol AS amino 
caproate. The enzyme histochemistry worked on paraffin sections, 
indeed I used it on glycol methacrylate sections, it was very 
selective for mast cells. I found it very useful to differentiate 
between PMNs and mast cells at sites of cartilage erosion in 
rheumatoid arthritis (I used naphthol AS -D chloroacetate to stain for 
PMNs and this substrate stains mast cells as well) you could visualise 
apparently extracellular mast cell granules in the region. Originally 
I got the substrate as a gift from Lung, but later I managed to get 
some substrate made by a pharmaceutical company. I remember that a lot 
of enzyme histochemistry was species specific in the sense that it 
worked in some mammals not others.

L T Yam et al    Eosinophilia in systemic mastocytosis. Am J Clin 
Pathol vol 73:48-54 (1980)

M Bromley and DE Woolley Histopathology of the rheumatoid lesion 
.Arthritis and Rheumatism vol 27 #8 857-863  (1984)

Mike Bromley
Histology Department
Paterson Institute
Wilmslow Road
Manchester
M20 9BX
UK