(KH) Response to Infection 1 2024 [Autosaved]

Response to Infection: Overview

• Infectious diseases are caused by pathogens (viruses, bacteria) invading hosts.

• Pathogens can spread through various mechanisms:

  • Direct contact

  • Indirect contact and touching contaminated objects

  • Transfer of body fluids

  • Disease-specific vectors

  • Contaminated food and water

Body's Defense Mechanisms

• The body utilizes several external defense systems against pathogens:

  • Skin: acts as a physical barrier, prevents pathogen entry.

  • Digestive Tract: acidity from HCl kills many pathogens in food.

  • Urogenital Tract: urine flushes out pathogens, preventing urinary tract infections.

  • Respiratory System: mucus traps inhaled particles, while hairs filter.

  • Ears & Eyes:

    • Tears and ear wax provide antibacterial properties.

• Non-specific immune responses include inflammation and fever.

Immunity

• Types of Immunity:

  • Passive Immunity: Acquired via antibodies from the placenta or serum injections.

  • Active Immunity: Developed through exposure to pathogens or vaccines.

• Immunity is established via the production of antibodies by B lymphocytes and cell-mediated responses by T lymphocytes, including memory cell creation.

Pathogens Overview

Bacteria:

• Many bacteria are harmless (non-pathogenic).

• Pathogenic bacteria can cause illness even in small amounts.

• Characteristics:

  • Single-celled

  • Microscopic, classified by shape.

  • Identification techniques involve agar plate culture.

Viruses:

• Extremely small; only visible with an electron microscope.

• Comprised of either DNA or RNA, surrounded by a protein coat.

• Infect living cells, leading to reproduction of the virus particles.

• Bacteriophages: viruses that infect bacteria, causing cell death.

Transmission of Pathogens

1. Direct Contact: physical interaction with an infected person.

2. Body Fluids: contact with infected fluids (e.g., blood).

3. Droplets: emission of airborne droplets containing pathogens.

4. Ingestion: consuming contaminated food or beverages.

5. Airborne: pathogen-laden particles travel through the air.

6. Vectors: pathogens are spread through insects or animals.

Non-Specific Defenses

Internal Defenses:

1. Phagocytosis: specialized white blood cells (leukocytes) that engulf pathogens.

   • Phagocytes like monocytes turn into macrophages to digest bacteria.

2. Inflammatory Response:

   • Triggered by tissue damage and involves increased blood flow, vasodilation, and immune cell activity.

   • Signs include redness, swelling, heat, and pain.

3. Fever: body's temperature rises in response to pathogens:

   • Hypothalamus is reset to a higher level by pyrogens.

   • Fever aids in fighting off infections but can become harmful if excessively high.

Preventing Pathogen Entry

Hygiene Practices:

• Regularly wash hands and cover mouth when sneezing.

• Maintain cleanliness of surfaces and personal belongings.

• Avoid sharing personal items.

Mechanical Barriers:

• Utilize protective equipment (masks, gloves) in high-risk situations.

• Wear appropriate clothing to prevent insect bites in endemic areas.

Hygiene Hypothesis

• Proposes that exposure to bacteria and germs during childhood is crucial for a well-functioning immune system.

• Observed trends include increased allergies and autoimmune diseases in overly sanitized environments.

Response to Infection: Overview

Infectious Diseases

Infectious diseases are caused by pathogens such as viruses and bacteria that invade hosts. These pathogens are constantly evolving and can adapt to overcome the host's defense mechanisms. Understanding the life cycle and characteristics of these pathogens is crucial for developing effective treatments and prevention strategies.

Mechanisms of Pathogen Spread

Pathogens can spread through various mechanisms:

• Direct Contact: Physical interaction with an infected person or surface.

• Indirect Contact: Contact through contaminated objects, including door handles, utensils, and medical equipment.

• Transfer of Body Fluids: Involves exposure to infected fluids such as blood, saliva, or other bodily secretions.

• Disease-specific Vectors: Insects or animals that carry and transmit the pathogens (e.g., mosquitoes transmitting malaria).

• Contaminated Food and Water: Consuming or coming into contact with food or water that has been tainted by pathogens, leading to outbreaks of diseases like cholera.

Body's Defense Mechanisms

The body utilizes several external defense systems against pathogens:

• Skin: Acts as a physical barrier and also secretes antimicrobial peptides that play a role in preventing pathogen entry.

• Digestive Tract: The acidity from hydrochloric acid (HCl) in stomach secretions kills many pathogens in food.

• Urogenital Tract: Urine flushes out pathogens to prevent urinary tract infections, and the acidic environment discourages pathogen growth.

• Respiratory System: Mucus traps inhaled particles and pathogens, while tiny hairs (cilia) in the respiratory tract help move trapped particles out of the lungs.

• Ears & Eyes: Tears have antibacterial properties and help wash away potential pathogens, while earwax provides a protective barrier in the ear canal.

• Non-specific immune responses: These include inflammation to isolate and eliminate pathogens and fever, which raises body temperature to inhibit pathogen replication.

Immunity

Types of Immunity:

• Passive Immunity: Acquired through antibodies received from the placenta during pregnancy or through serum injections (e.g., antivenom).

• Active Immunity: Developed through exposure to pathogens or through vaccinations, prompting the body to produce its own antibodies. This form of immunity can be long-lasting and provides specific protection against future infections.

Immunity is established via the production of antibodies by B lymphocytes and cell-mediated responses by T lymphocytes. Memory cells created during this process play a crucial role in recognizing and quickly responding to previously encountered pathogens.

Pathogens Overview

Bacteria:

• Many bacteria are harmless (