Final answer:
In a sample with predominant collagen using MTS stain, counterstains like light green or Biebrich scarlet-acid fuchsin should be used for better differentiation. Methylene blue is not as effective because it can mask the collagen staining due to its blue color.
Step-by-step explanation:
When collagen is predominant in a sample undergoing MTS stain (Masson's Trichrome Stain), the preferred counterstain is typically a light green or Biebrich scarlet-acid fuchsin combination rather than methylene blue.
This is because these counterstains provide a clear contrast to the blue or green stained collagen fibers, enhancing the differentiation between collagenous and non-collagenous components of the tissue.
On the other hand, methylene blue might not offer as clear of a contrast because it also imparts a blue color which can mask the collagen staining.
The Masson's Trichrome Stain itself is used to differentiate between collagen and muscle fibers, as collagen is stained blue or green depending on the particular variant of the stain, while muscle fibers are stained red. In the context of AFB staining methods like the Ziehl-Neelsen or Kinyoun, which determine the presence of acid-fast bacteria, the tissue cells are contrasted with a secondary counterstain such as methylene blue.