Lecture 15_14March2025_after class

  • Q&A style Zoom sessions:

    • Monday: 5-6 PM

    • Tuesday: 7-8 PM

  • Bring questions for clarification

Lecture Agenda

  • Review of Lecture 14: Measles

  • Lecture 15 Topics:

    • Overview of the Immune System

    • Innate Host Defenses

    • Acute Inflammatory Response

    • Phagocytosis

    • Fever

    • The Complement System

Measles: Cause, Symptoms, Treatment, and Prevention

  • Highly contagious, particularly dangerous for infants

  • Symptoms: High fever, cough, runny nose, red eyes, followed by a rash

  • Treatment: Supportive therapy

  • Prevention: MMR vaccine

    • One dose effective in 93% of cases at 12-15 months

    • Two doses boost effectiveness to 97% at ages 4-6

Epidemiology of Measles

  • Notable Case: January 2020 NU student in Boston diagnosed

  • Public exposure list included locations and times to identify potential outbreak

Phagocytosis Overview

  • Phagocytosis: key immune response involving engulfing and destroying foreign invaders

  • Recognition: Phagocytes distinguish between self and non-self, aided by proteins like CD47

Innate Immune System Components

  • Security Walls: Skin and mucous membranes act as barriers

  • Sensor Systems: Detect damage and microbial invasion through Pattern Recognition Receptors (PRRs)

  • Effector Actions: Immune response includes interferon production, phagocytosis, antimicrobial substances, and activation of the complement system

Inflammation and Its Roles

  • Inflammation: Critical innate defense process against invaders

  • Allows phagocytic cells to infiltrate infected tissues via extravasation

  • Cardinal signs: Heat, edema, redness, pain, and altered function (HERPA)

The Acute Inflammatory Response: Mechanisms

  • Initiated by vasoactive factors from macrophages leading to vasodilation

  • Involves neutrophils and other immune responses to eliminate pathogens

  • Chronic inflammation results from persistent foreign bodies or irritants

    • Example pathogens: Mycobacterium tuberculosis

The Complement System

  • Composed of 20 proteins, crucial for preventing blood infections

  • Activation leads to multiple outcomes like forming Membrane Attack Complexes (MACs) to lyse cells

  • Pathways of activation:

    • Classical: Requires antibodies

    • Alternative: Does not require antibodies

    • Lectin: Requires mannose-binding lectin due to macrophage-induced cytokines

Fever: Induction and Advantages

  • Fever (above 38ºC or 100.4ºF) is part of immune response to regulate pathogen growth

  • Pyrogens (external and internal) stimulate hypothalamus to raise body temperature

  • Key advantages of fever: Disrupts microbial growth and reduces available iron

Discussion Points

  • Case studies illustrating the difference in immune responses:

    • Example of a healthy child vs. an adult with liver disease illustrates the impact of innate immunity

    • Importance of early identification of infections and immune responses in clinical settings.