<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<br> Yesterday, someone (I forgot who, I went delete
happy) asked the difference between the Schmorls histochemical (HC) stain
and the immunohistochemical (IHC) stains S100 and HMB45.
<br> The main difference is specificity. The immuno methods
are very specific, HMB45 stains only melanosomes, and S100 stains only
neurologically derived cells. Schmorls will stain reducing substances.
This means melanin, argentaffin and any substance with a lower pH than
the staining solution.
<br> Sheehan notes in <u>Theory and Practice of Histotechnology</u>
that, "A positive reaction is presumptive evidence of the presence of melanin,
though other reducing substances react, including ascorbic oxalic and uric
acids, phenols, indoles, aryl amines, thiols and others." (pg 223)
<br> I do think that some of these results could be done
without the benefit of the IHC techniques, but there are occasions where
the IHC is needed and preferred over the HC method.