Which stain stains the cytoplasm of plasma cells rose?

• A. Methyl green-pyronin
• B. Toluidine blue
• C. Hematoxylin
• D. Eosin

Answer: (A)

The key idea is that certain stains can differentiate nucleic acids to reveal cellular components. Methyl green-pyronin is a dual stain where methyl green binds DNA and stains it green, while pyronin Y binds RNA and stains it rose (pink-red). Plasma cells are rich in cytoplasmic RNA due to abundant ribosomes and rough endoplasmic reticulum, so their cytoplasm takes on a rose color with this stain. This creates a distinct contrast: a green nucleus with rose-colored cytoplasm, making plasma cells stand out. Other stains don’t highlight this RNA-rich cytoplasm in the same rose hue—hematoxylin mostly colors nuclei blue, eosin colors general cytoplasm pink but not specifically RNA-rich cytoplasm as rose, and toluidine blue provides blue staining with metachromasia rather than the characteristic rose cytoplasm of plasma cells.