Which dyes stain weakly sulfated goblet cells?

• A. Alcian blue 2.5, metachromatic pH 2.0, colloidal iron
• B. Alcian blue 1.0, metachromatic pH 1.5
• C. Toluidine blue
• D. Hematoxylin counterstain

Answer: (A)

Staining weakly sulfated goblet cells relies on detecting acidic groups in mucins, including limited sulfate content. Alcian blue at pH 2.5 binds acidic mucopolysaccharides, which include both sulfated and carboxylated mucins. Weakly sulfated goblet cells often carry enough carboxylate groups to be picked up by this stain, making them visible.

Metachromasia with a basic dye at a very low pH (around 2.0) is sensitive to sulfated residues. Even with only light sulfation, the high density of sulfated groups can produce a metachromatic color shift, helping reveal these goblet cells that might be less evident with other stains.

Colloidal iron binds to sulfate groups, providing another modality that highlights sulfated mucins. This can enhance visualization of goblet cells with weaker sulfation that might be missed by other methods.

Together, these stains complement each other: Alcian blue marks acidic mucins broadly; metachromasia at low pH emphasizes sulfates; and colloidal iron specifically tags sulfated groups. This combination best reveals weakly sulfated goblet cells.