Questions and Answers
What type of cancer recurrence is indicated in this case?
Which immunohistochemical markers were expressed by the malignant cells?
What is a potential serious side effect of using Tamoxifen?
What mechanism does Tamoxifen use to limit cancer cell behavior?
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Which statement about hormone receptors in breast cells is accurate?
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What is the main purpose of immunohistochemistry?
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Who is credited with developing the immunohistochemistry technique?
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Which type of labels has improved localization in immunohistochemistry for light microscopy?
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What does an antigen do?
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How do antibodies specifically recognize antigens?
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What structural part of an antibody is common to all antibodies of a specific species?
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What role does autoradiography play in immunohistochemistry?
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For a given protein sequence, how many antibodies typically recognize it?
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What mechanism best describes the interaction between an antibody and an antigen?
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Which immunoglobulin is the most prominent in mammals?
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What is the primary characteristic of polyclonal antibodies?
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How are monoclonal antibodies produced?
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What is the sensitivity of monoclonal antibodies in immunology?
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In immunohistochemistry, what does specificity refer to?
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Which technique uses a labelled antibody directly for immunofluorescence?
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What was a significant advancement related to the labeling of antibodies?
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What is the function of horse-radish peroxidase in immunohistochemistry?
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What does the ABC method stand for in immunohistochemistry?
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What type of serum is used to block nonspecific binding sites in tissue?
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What is FITC in relation to immunohistochemistry?
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What is the role of biotin in immunohistochemistry?
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What is the main purpose of antigen retrieval methods like PIER and HIER?
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How does avidin amplify signal detection in the ABC method?
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What is the main disadvantage of using the avidin-biotin complex in immunohistochemistry?
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What is the role of Normal Goat Serum (NGS) in immunohistochemistry?
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What does the term 'grading' refer to in tumor classification?
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What is a characteristic of adenocarcinoma?
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What does PIER stand for in antigen retrieval?
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How does formalin fixation affect tissue samples?
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Which method uses heat to retrieve antigens masked by formalin fixation?
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What is the significance of using controls in immunohistochemistry?
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What is a common characteristic of well-differentiated tumors?
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What does external quality control in immunohistochemistry entail?
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In the context of tumor diagnosis, what does a 'mass' typically refer to?
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Study Notes
Immunohistochemistry Overview
- Immunohistochemistry (IHC) localizes antigens or proteins in tissue sections using labeled antibodies through antigen-antibody interactions.
- Enables visualization of specific cellular components within cells or tissues.
Historical Development
- Developed by Albert Coons and colleagues in 1941; first identified pneumococci using a direct fluorescent method.
- Technique evolved to include enzyme labels for light microscopy and heavy metals for electron microscopy.
Antibody and Antigen Interaction
- Antigens induce immune responses; antibodies (immunoglobulins) bind specifically to antigens.
- Antibodies recognize antigens via small amino acid chains known as epitopes. Each protein sequence typically has multiple antibodies targeting different epitopes.
Antibody Structure
- Antibodies feature a constant region common to all antibodies of a species and a variable region unique to specific epitopes.
- The paratope is the binding site on an antibody that interacts with the epitope of an antigen; binds through a lock and key mechanism.
Types of Antibodies
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Polyclonal Antibodies
- Produced by immunizing animals (e.g., rabbits) with an antigen.
- Highly sensitive but exhibit poor specificity; a mixture of antibodies targeting different epitopes.
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Monoclonal Antibodies
- Created by fusing splenic B cells with myeloma cells to form hybridomas, producing identical antibodies.
- Highly specific for a single epitope but typically less sensitive.
Key Concepts in Immunohistochemistry
- Direct Method: Uses a labeled antibody directly for immunofluorescence, but historically lacked specificity.
- Indirect Method: Involves a primary antibody against an antigen, followed by a secondary antibody. Enables amplification of signals.
Signal Amplification Methods
- ABC method utilizes avidin (a biotin-binding protein) and biotin to enhance signal detection; amplifies the signal significantly but can cause steric issues.
- Modern techniques use a polymer backbone for signal amplification, addressing steric problems and improving specificity.
Antigen Retrieval Techniques
- HIER (Heat-Induced Epitope Retrieval): Employs heat to restore antigen sites masked by formalin fixation.
- PIER (Proteolytic Epitope Retrieval): Uses enzymes to retrieve antigens obscured by chemical changes.
Immunohistochemistry Workflow
- Steps include tissue preparation, antigen retrieval, protein blocking, antibody incubation, chromogen application, and mounting for visualization.
- Blocking non-specific binding sites is crucial to prevent background signals.
Quality Control in Immunohistochemistry
- Internal controls involve positive and negative controls to verify the accuracy of staining procedures.
- External quality control assesses laboratory performance through programs like UK NEQAS ICC & ISH.
Tumor and Carcinoma Context
- Carcinomas are tumors formed from malignant epithelial cells, ranging in differentiation levels.
- Adenocarcinoma: A type of carcinoma developed from glandular cells.
- Grading classifies tumors based on differentiation; well-differentiated tumors appear more normal, while poorly differentiated ones exhibit immature characteristics.
Clinical Case Applications
- Liver Mass Case: A 59-year-old male diagnosed with poorly differentiated adenocarcinoma; immunohistochemistry distinguished the primary tumor, revealing it as gastric adenocarcinoma.
- Breast Cancer Recurrence Case: A 66-year-old woman with a history of breast cancer; IHC confirmed recurrence indicating ductal adenocarcinoma, utilizing estrogen/progesterone receptor staining and HER2 expression testing.
Pharmacological Considerations
- Tamoxifen is used to block hormone receptors in breast cancer treatment but may increase endometrial cancer risk.
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Description
Explore the fundamentals of immunohistochemistry (IHC), a technique used to identify proteins in tissue sections with labeled antibodies. Understand its historical development, antibody-antigen interactions, and the unique structure of antibodies. This quiz will test your knowledge on these essential concepts in IHC.
