True. The avidin-biotin complex (ABC) method is highly sensitive but has a well-known drawback: it can produce significant non-specific background staining in tissues with high levels of endogenous biotin. Biotin (vitamin B7) is a coenzyme involved in carboxylation reactions and is abundant in the mitochondria of hepatocytes (liver), renal tubular cells (kidney), and adipocytes (fat). In the ABC method, the final detection complex contains avidin, which has an extraordinarily high affinity for biotin. If endogenous biotin in the tissue is not blocked, the avidin-enzyme complex can bind directly to these tissue sites, bypassing the antibody steps entirely. This leads to diffuse, granular cytoplasmic staining unrelated to the target antigen. To mitigate this, a biotin-blocking step (sequential incubation with avidin, then biotin) can be used prior to the ABC step. Alternatively, many labs now prefer polymer-based detection systems (like EnVision) that do not use the biotin-avidin interaction, thereby eliminating this source of background.

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Zambia

• Joseph Soko – 101 pts

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