The primary purpose of counterstaining in an IHC procedure is to provide contrast and allow visualization of the tissue's overall cellular architecture. After the specific antigen has been stained with a colored chromogen (like brown DAB), the rest of the tissue would be nearly colorless, making it difficult to identify individual cells, locate nuclei, or assess tissue morphology. A counterstain is a general histological stain, most commonly hematoxylin, which stains cell nuclei a blue-purple color. This creates a stark visual contrast against the specific stain, allowing the pathologist to easily see the context of the positive signal: Is it in the nucleus, cytoplasm, or membrane? What percentage of cells are positive? What is the tissue structure? Without a counterstain, interpreting the IHC slide accurately would be very challenging. The counterstain is typically applied as the final step before dehydration and mounting.

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Zambia

• Chita katowando – 271 pts

• Visual Pathway Lesions
• Positive and Negative Symptoms
• Hallucinations and Delusions
• Antipsychotic Medications
• Emergency: Environmental Emergencies