Immunohistochemistry Overview
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Questions and Answers

What type of cancer recurrence is indicated in this case?

  • Prostate cancer
  • Colorectal cancer
  • Ductal adenocarcinoma of the breast (correct)
  • Lung cancer

    • Which immunohistochemical markers were expressed by the malignant cells?

  • CK20 and TTF1
  • CDX2 and Her2
  • Progesterone and CDX2
  • CK7 and hormone receptors (correct)

    • What is a potential serious side effect of using Tamoxifen?

  • Increased weight gain
  • Decreased bone density
  • Increased risk of ovarian cancer
  • Increased risk of endometrial cancer (correct)

    • What mechanism does Tamoxifen use to limit cancer cell behavior?

    <p>It blocks estrogen receptors.</p> Signup and view all the answers

    Which statement about hormone receptors in breast cells is accurate?

    <p>Breast cells have receptors throughout the normal menstrual cycle.</p> Signup and view all the answers

    What is the main purpose of immunohistochemistry?

    <p>To visualize the distribution and localization of specific cellular components</p> Signup and view all the answers

    Who is credited with developing the immunohistochemistry technique?

    <p>Albert Coons</p> Signup and view all the answers

    Which type of labels has improved localization in immunohistochemistry for light microscopy?

    <p>Enzyme labels</p> Signup and view all the answers

    What does an antigen do?

    <p>Induces an immune response</p> Signup and view all the answers

    How do antibodies specifically recognize antigens?

    <p>By binding to small, specific amino acid chains called epitopes</p> Signup and view all the answers

    What structural part of an antibody is common to all antibodies of a specific species?

    <p>Constant region</p> Signup and view all the answers

    What role does autoradiography play in immunohistochemistry?

    <p>It visualizes radioactive labels</p> Signup and view all the answers

    For a given protein sequence, how many antibodies typically recognize it?

    <p>Multiple antibodies</p> Signup and view all the answers

    What mechanism best describes the interaction between an antibody and an antigen?

    <p>A lock and key mechanism</p> Signup and view all the answers

    Which immunoglobulin is the most prominent in mammals?

    <p>IgG</p> Signup and view all the answers

    What is the primary characteristic of polyclonal antibodies?

    <p>They consist of antibodies targeting different epitopes.</p> Signup and view all the answers

    How are monoclonal antibodies produced?

    <p>By fusing splenic B cells with myeloma cells.</p> Signup and view all the answers

    What is the sensitivity of monoclonal antibodies in immunology?

    <p>Low sensitivity</p> Signup and view all the answers

    In immunohistochemistry, what does specificity refer to?

    <p>The ability to selectively bind to a single epitope</p> Signup and view all the answers

    Which technique uses a labelled antibody directly for immunofluorescence?

    <p>Direct method</p> Signup and view all the answers

    What was a significant advancement related to the labeling of antibodies?

    <p>Using enzymes for labeling</p> Signup and view all the answers

    What is the function of horse-radish peroxidase in immunohistochemistry?

    <p>It catalyzes oxidation of chromogens</p> Signup and view all the answers

    What does the ABC method stand for in immunohistochemistry?

    <p>Avidin-Biotin Complex</p> Signup and view all the answers

    What type of serum is used to block nonspecific binding sites in tissue?

    <p>Normal serum from the same species as the secondary antibody</p> Signup and view all the answers

    What is FITC in relation to immunohistochemistry?

    <p>A fluorescent marker</p> Signup and view all the answers

    What is the role of biotin in immunohistochemistry?

    <p>It serves as a coenzyme for metabolic reactions</p> Signup and view all the answers

    What is the main purpose of antigen retrieval methods like PIER and HIER?

    <p>To unmask antigenic sites hidden due to chemical changes</p> Signup and view all the answers

    How does avidin amplify signal detection in the ABC method?

    <p>By forming multiple complexes with biotin</p> Signup and view all the answers

    What is the main disadvantage of using the avidin-biotin complex in immunohistochemistry?

    <p>It can mask antigenic sites due to steric hindrance</p> Signup and view all the answers

    What is the role of Normal Goat Serum (NGS) in immunohistochemistry?

    <p>To block non-specific antibody binding</p> Signup and view all the answers

    What does the term 'grading' refer to in tumor classification?

    <p>The degree of differentiation of tumor cells</p> Signup and view all the answers

    What is a characteristic of adenocarcinoma?

    <p>It originates from glandular epithelial cells</p> Signup and view all the answers

    What does PIER stand for in antigen retrieval?

    <p>Proteolytic Epitope Retrieval</p> Signup and view all the answers

    How does formalin fixation affect tissue samples?

    <p>It causes cross-linkages that hide antigenic sites</p> Signup and view all the answers

    Which method uses heat to retrieve antigens masked by formalin fixation?

    <p>Heat-Induced Epitope Retrieval (HIER)</p> Signup and view all the answers

    What is the significance of using controls in immunohistochemistry?

    <p>To validate the staining process and manage artifacts</p> Signup and view all the answers

    What is a common characteristic of well-differentiated tumors?

    <p>They display almost normal behavior and structure</p> Signup and view all the answers

    What does external quality control in immunohistochemistry entail?

    <p>Involvement in programs for performance assessment against standards</p> Signup and view all the answers

    In the context of tumor diagnosis, what does a 'mass' typically refer to?

    <p>A collection of malignant cells forming a tumor</p> Signup and view all the answers

    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

    • 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.
    • 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.

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