Which tissue serves as a control for Alcian blue 2.5 staining?

• A. Unautolyzed small intestine, appendix or colon
• B. Autolyzed liver
• C. Fresh brain tissue
• D. Skeletal muscle

Answer: (A)

Alcian blue 2.5 binds acidic mucopolysaccharides, which are abundant in goblet cells of mucosal surfaces. To verify the stain is working, you use tissue that reliably contains these mucins. The unautolyzed mucosa of the gastrointestinal tract—such as the colon, appendix, or small intestine—provides a strong positive control because its goblet cells are rich in acidic mucins and will stain blue with Alcian blue 2.5.

Autolyzed liver, fresh brain tissue, or skeletal muscle either lack significant mucin content or have degraded mucins, making them poor controls for this stain.