ELISA and Immune Responses in Infectious Diseases

ELISA Simulation Kit Overview

  • Students engage with the ELISA (Enzyme-Linked Immunosorbent Assay) Simulation Kit to learn about antibody-mediated human immunity.

  • ELISA is utilized to test blood serum for the presence of antibodies against disease-causing pathogens, such as viruses and bacteria.

  • The assay offers an indirect detection method for infections by particular pathogens.

  • Students undertake a hands-on simulation using simulated reagents to diagnose fictitious patients for diseases like HIV, Lyme Disease, Avian Influenza (Bird Flu), or West Nile Virus.

  • Hypothetical patient scenarios are presented for each of the diseases tested.

  • The kit is simulated and does not include actual serum samples, antibodies, pathogens, or disease agents, ensuring there is no risk of infection.

Learning Objectives

  • Understand the basic principles of antibody-mediated immunity.

  • Comprehend the steps involved in performing an ELISA and its application as a diagnostic tool.

  • Determine the nature and transmission patterns of certain infectious diseases.

Body's Defense System

  • The human body employs multiple lines of defense against infection caused by pathogenic organisms.

    • Pathogens:

    • Pathogens are disease-causing agents such as viruses, bacteria, protozoa, fungi, and other microorganisms.

    • They invade the body, multiply, and can result in illness or death.

    • The body has three levels of defense:

    • First two levels are nonspecific defenses, which include physical barriers and innate immune responses.

    • The third level is the specific immune system, designed to target specific pathogens.

Specific and Nonspecific Barriers

Primary Defense Mechanisms

  • The skin and mucous membranes serve as the primary defense against pathogens.

    • Physical Barriers:

    • Skin acts as a protective covering against foreign invaders.

    • Mucous membranes line openings of the body (mouth, nostrils) and create additional barriers.

    • Secretions:

    • Secretions such as sweat and tears can inhibit pathogen entry.

Nonspecific Immune Responses

  • If external barriers are breached, the body activates several internal nonspecific immune responses:

    • Fever:

    • A physiological response where body temperature rises.

    • Pathogens often can't survive at elevated temperatures, thus slowing infection spread.

    • Inflammatory Response:

    • This response increases blood flow to the affected area, causing redness and swelling.

    • White blood cells (neutrophils) gather at the site of infection, employing phagocytosis to engulf invading organisms.

    • Neutrophils are accompanied by macrophages, which are larger phagocytic cells.

    • Other components include:

    • Complement System: Antimicrobial proteins that directly destroy pathogens.

    • Interferons: Proteins that enhance immune response, providing protection against viral infections.

    • Nonspecific defenses can recognize and distinguish between self and non-self cells, providing a mechanism to eliminate abnormal body cells (potentially cancerous).

    • Natural Killer Cells:

    • A vital part of nonspecific cell-mediated immunity, attacking abnormal and infected cells.

Specific Immune Response

  • The specific immune system is highly complex and involves many organs and tissues, including the thymus, spleen, lymph nodes, bone marrow, and various white blood cells.

    • Antigens:

    • Microbes and other molecules that trigger immune responses.

    • Key participants:

    • Dendritic Cells and Macrophages: Break down pathogens and present antigen fragments on their surfaces.

    • B lymphocytes (B cells) and T lymphocytes (T cells): White blood cells that are essential for the specific immune response.

    • Antibodies: Proteins produced by B cells, often referred to as immunoglobulins, that bind to specific antigens.

      • Antibodies have a Y-shaped structure and different binding sites designed to fit specific antigens, emphasizing their role in forming antigen-antibody complexes (the lock-and-key mechanism).

Chapter 9 Terms

  • Sinusitis: Inflammation of a sinus due to various agents (viruses, bacteria, allergies).

  • Pharyngitis: Inflammation of the pharynx, causing a sore throat.

  • Epiglottitis: Infection of the epiglottis, potentially leading to airway obstruction.

  • Laryngitis: Viral infection of the larynx associated with mild upper respiratory symptoms.

  • Bronchitis: General inflammation of bronchi with symptoms like fever and cough.

  • Bronchiolitis: Inflammation of the membranes lining bronchioles.

  • Pneumonia: Disease marked by lung inflammation due to various infectious agents.

    • CAP (Community-Acquired Pneumonia): Most common type contracted outside healthcare facilities.

    • HAP (Healthcare-Associated Pneumonia): Acquired in healthcare settings.

    • VAP (Ventilator-Associated Pneumonia): Contracted while on mechanical ventilation.

  • Aspiration Pneumonia: Due to inhalation of foreign materials.

  • Tuberculosis (TB): Airborne disease caused by tubercle bacteria affecting mainly the respiratory system.

  • Bioterrorism: Use of biological agents against civilian targets.

  • Influenza (Flu): Contagious viral illness caused by influenza A virus, noted for subtypes such as H5 known as bird flu.