What tissue was used as the positive control for KIT staining?

• A. Canine cerebellum
• B. Canine liver
• C. Feline cortex
• D. Equine spleen

Answer: (A)

In immunohistochemistry, a positive control tissue shows that the antibody and staining procedure are working as intended by producing the expected labeling of cells that normally express the target antigen. For KIT staining, canine cerebellum is used because it reliably expresses KIT in specific cerebellar cells, yielding a consistent, detectable pattern. This provides a dependable benchmark: if the cerebellar tissue shows the anticipated KIT staining, you can trust that the staining protocol, antigen retrieval, and detection steps are functioning properly in your run.

The usual takeaway is that the positive control should have known, robust KIT expression to confirm the assay is performing. If you don’t see staining in the cerebellum, the issue could lie with the primary antibody, the detection system, fixation, or other technical steps, rather than with the tissue being tested.

Other tissues may not offer the same reliability for KIT as a positive control because KIT expression can be sparse or variable across different organs and species. Using tissue with inconsistent expression makes it harder to interpret whether a negative result in test samples reflects a true absence of antigen or a technical problem with the staining.