Immunohistochemistry Flashcards
6 cards from real ASCP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Immunohistochemistry flashcards as text
What does a negative IHC result on a poorly fixed specimen most likely represent?
Answer: False negative due to antigen destruction by inadequate fixation
Inadequate fixation causes protein degradation that destroys antigenic epitopes, resulting in false-negative IHC results even when the antigen is present.
In IHC, what is the function of the blocking step with normal serum?
Answer: To prevent non-specific binding of the secondary antibody to tissue proteins
Normal serum (from the species used to raise the secondary antibody) saturates non-specific protein binding sites, reducing background staining.
Ki-67 IHC is used to assess what cellular property?
Answer: Cellular proliferation index
Ki-67 is a nuclear protein expressed only in proliferating cells; IHC for Ki-67 measures the proportion of actively dividing cells (proliferation index).
What is the difference between the direct and indirect IHC methods?
Answer: Direct uses enzyme-labeled primary antibody; indirect uses unlabeled primary and enzyme-labeled secondary antibody
In the direct method, the primary antibody carries the detection label; in the indirect method, an unlabeled primary antibody is detected by a labeled secondary antibody for greater sensitivity.
What IHC marker is used to confirm the presence of muscle differentiation in a tumor?
Answer: Desmin or smooth muscle actin (SMA)
Desmin and smooth muscle actin are cytoskeletal proteins expressed in muscle cells; their IHC positivity confirms muscle differentiation in tumor cells.
Over-retrieval in heat-induced antigen retrieval (HIER) can cause which artifact?
Answer: Section detachment from the slide
Excessive heat or prolonged retrieval times can cause sections to detach from slides, especially if adhesion is suboptimal.