Immunology Quiz: Antibodies and the Immune System

Lecture 8: Introduction to Clinical Virology & Immunology

• Learning Objectives: Understand viral pathogenesis, common viral infections, laboratory techniques in clinical virology, and basic immunology in the context of infection.
• Clinical Virology: The study of viruses and their impact on human health, encompassing diagnosis, treatment, and prevention of viral diseases. It's critical for public health enabling early detection of infections, development of tests, therapies, and vaccines. Clinical virology also helps understand viral evolution, transmission, and emerging pathogens.
• Viral Pathogenesis: Host cells respond to viral infections in three ways: no effect (asymptomatic), cytopathic (morphological changes due to viral replication and cell death), and oncogenic (loss of cell replication control). Viral infections can cause localized or disseminated disease. Virus entry can spread through the bloodstream (viremia).
• Diagnostic Methods (Virology): Testing methods are grouped into three categories: Direct Detection (electron microscopy, antigen detection -immunofluorescence, histological changes), Indirect Examination (virus isolation), and Serology (measuring antibodies). Viruses cannot be cultured on artificial media.
• Molecular Detection: Techniques depend on whether the virus has DNA or RNA genomes. These methods usually involve sample collection, sample processing, viral isolation, RNA extraction (if RNA genome), creating cDNA (if RNA genome), and amplifying the DNA/RNA using PCR.
• Serology: Detecting antibodies to specific viruses. The first antibody to appear is IgM. Later, IgG antibodies develop. Serology can identify a past or present viral infections.
• Immune Response: Immunology studies the body's genetic, biological, chemical, and physical characteristics. Immunity is a body's ability to respond to foreign substances.
• Immunology Key Terms:
  • Immunity: The body's ability to respond to foreign substances.
  • Immunocompetent: When the immune system functions correctly.
  • Immunosuppressed: When part of the immune system cannot respond to challenges.
  • Antigen: Any molecule triggering an immune response.
  • Epitope: The smallest part of an antigen binding to an antibody.
  • Antibody: Protective proteins that target foreign substances.
  • Immunogen: Any molecule capable of stimulating antibody production.
  • Allergen: A substance causing an allergic reaction.
  • Autoantigen: Self-antigens targeted by the immune system (causing autoimmune disease).
  • Tumor antigen: Protein on cancerous cells.
• Innate Immunity: The body's first line of defense against pathogens. Rapid and non-specific response, Cells involved include phagocytes, monocytes (macrophages), mast cells, neutrophils, dendritic cells, natural killer cells, basophils, and eosinophils.
• Innate Immunity—Complement System: Proteins produced by the liver, circulating in the blood until they encounter pathogens, working collectively to destroy them. Three complement pathways—classic, alternative, lectin—are based on distinct triggers (antibody-antigen interactions, pathogen surface molecules, and mannose-binding lectin).
• Innate Immunity—Other Key Proteins (TL-Receptors): A family of transmembrane receptors (TLRs). They identify Pathogen-Associated Molecular Patterns (PAMPs) and Damage-Associated Molecular Patterns (DAMPs) (from dying cells) triggering inflammation.
  • Cytokines: Small proteins mediating the immune response. Types include Colony-Stimulating Factors (CSF), Interferons, Interleukins (IL), Chemokines and Tumor Necrosis Factor (TNF).
• Acute Inflammation: A protective mechanism triggered by injury or infection.
• Acute vs Chronic Inflammation: Differentiated by type of initiating cells, the duration of the response, and the severity and progression of the inflammatory response.
• Adaptive Immunity: This type of immunity is the body's acquired immunity. It develops later in life and adapts to new infections, requiring antigens, cells (B-cells and T-cells), antibodies, receptors, and immune responses.
  • Antigens: Any foreign macromolecule specifically recognized by the immune system.
  • Antibodies: Proteins produced by B-cells to specifically bind to antigens.
  • B-cells: Develop in the bone marrow, producing antibodies directed against specific antigens.
  • T-cells: Crucial for cell-mediated immunity. Recognize antigens presented on cells.
• Antibodies: Types such as IgM, IgG, IgA, IgD, IgE and how they function
• T Cell-Dependent Activation of B cells: How B-cells are activated when a helper T-cell assists.
• T Cell-Independent Activation of B cells: How B-cells become activated even without assistance from T-cells.
• Case Studies: Examples of different viral infections and potential tests to determine the causative agent.
• Vaccination: An artificially acquired active immunity which strengthens the immune system's response against the antigen.
  • Types of vaccines: Attenuated microbes, killed or fragmented microbes, and toxins.

Specific Cases

• Viral Gastroenteritis (Case 1): Viral cause (likely Norovirus) suspected due to multiple simultaneous illnesses seemingly linked to a common source (a birthday party and swimming pool).
• Hepatitis (Case 2): Hepatitis B, C, or D are possible diagnoses, considering the needle-stick exposure. The serology test results are critical for diagnosis, especially the IgM.