Infectious Diseases and Immune Response

Introduction to Infectious Diseases

  • Overview of how infectious diseases affect the body.

  • Identification of agents and vectors involved in the transmission of infectious diseases.

Understanding Infections

  • Definition of infections:

    • Caused by pathogens, which are disease-causing organisms.

  • Pathogens are classified as microorganisms, including:

    • Viruses

    • Parasites

  • Pathogens thrive in a warm and nutrient-rich environment, which facilitates their growth.

Vectors in Disease Transmission

  • Definition of vectors:

    • Biological or physical carriers that transport pathogens to hosts.

    • Serve as means of pathogen transmission.

  • Example of vector transmission:

    • Flies can carry pathogens from fecal matter to food, leading to transmission of diseases when contaminated food is consumed.

    • Example: A fly landing on a burger after picking up pathogens can lead to foodborne illness.

  • Mosquitoes as vectors:

    • Mosquito bites can transmit viruses; an infected mosquito can transfer the disease to a new host.

Vaccinations and Their Role

  • Definition of vaccination:

    • Vaccinations involve administering non-active viruses to stimulate the immune response without causing the disease.

Agents of Infection

  • Viruses as agents of infection:

    • Examples of viral diseases include:

    • Flu

    • Hepatitis

    • HIV

      • Mode of transmission includes sexual contact with contaminated fluids.

  • Importance of personal hygiene in preventing STIs:

    • Maintaining cleanliness can prevent infections such as athlete's foot.

    • Avoid contact with infected individuals, especially concerning STIs.

    • Regular STI testing is emphasized as crucial for health.

Infection Process

  • The stages of infection include:

    • Incubation period:

    • Time from initial exposure to pathogen until first symptoms appear.

    • Pathogen multiplies unnoticed by the host.

    • Prodromal stage:

    • Onset of non-specific symptoms like fatigue, low-grade fever, aches.

    • Characteristic symptoms may include rashes or severe cough.

    • Active illness stage:

    • The phase in which the infection is most active, with specific symptoms.

    • The immune system responds to the invading pathogens.

Immune Response

  • Description of the immune response mechanism:

    • Upon infection, the innate immune system responds immediately:

    • Releases chemical signals that trigger inflammation.

    • Symptoms of inflammation include redness, warmth, and swelling at the site of infection.

    • Types of immune cells involved:

    • Macrophages:

      • Engulf and destroy pathogens.

    • Neutrophils:

      • Move towards the infection site to neutralize pathogens.

  • If the infection continues, the adaptive immune system engages:

    • B cells produce antibodies to neutralize invading pathogens.

    • T cells assist in preventing spread.

Inflammation Process

  • Definition of inflammation as a local immune response to injury or infection:

    • Symptoms include heat, redness, edema, pain, and loss of function.

  • Inflammation sequence:

    1. Vasoconstriction:

    • Brief constriction of local blood vessels occurs.

    1. Vasodilation:

    • Chemicals like prostaglandins and histamine are released, causing dilation of blood vessels.

    • Increased blood flow to the area aids in healing.

    1. Increased capillary permeability:

    • Allows fluids and proteins from the blood to enter tissues.

    1. Chemotaxis:

    • Circulating immunity cells, particularly neutrophils, migrate to infection site via chemotactic signals.

    1. Diapedesis:

    • Neutrophils squeeze through gaps in the endothelium of blood vessels.

    1. Phagocytosis:

    • Neutrophils engulf and destroy bacteria at the injury site.

  • Tissue repair follows after bacterial destruction, involving fibroblast division and collagen secretion.

Anti-inflammatory Treatments

  • Definition of anti-inflammatory drugs:

    • These drugs inhibit inflammation by blocking the production of inflammatory chemicals.

  • Common anti-inflammatory drugs:

    • Non-Steroidal Anti-Inflammatory Drugs (NSAIDs):

    • Examples include Aspirin and Ibuprofen.

    • Contain an enzyme called cyclooxygenase (COX) that limits the production of inflammatory chemicals like prostaglandins, thus reducing symptoms of inflammation like pain and edema.