The critical step for removing paraffin and rehydrating tissue sections before IHC staining is **deparaffinization and rehydration through graded alcohols**. Tissue samples for histopathology are routinely embedded in solid paraffin wax to support them for thin sectioning. Before any staining can occur, this wax must be completely removed to allow aqueous-based reagents (like antibodies and buffers) to penetrate the tissue. This is achieved by immersing the slides in a series of baths: first in xylene or a xylene substitute (which dissolves the paraffin), then in progressively lower concentrations of alcohol (e.g., 100% ethanol, then 95%, then 70%), and finally in water. This gradual series replaces the organic solvent with water, rehydrating the tissue. If paraffin remains, it will create a barrier, leading to poor antibody penetration, weak staining, or complete staining failure.

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Zambia

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