12

Introduction

  • Greeting to students and note on iClicker usage

    • iClicker is optional and for fun, not graded.

    • Reminder to select the University of Guelph College of Biological Sciences as the primary institution to avoid fees.

Overview of Immunity

  • Three Key Lines of Defense in Immunity:

First Line of Defense

  • Definition: Nonspecific physical and chemical surface barriers.

  • Examples:

    • Skin: Prevents harmful microbes/toxins from entering the body.

    • Mucous membranes: Protect passages through the body (e.g., respiratory tract).

  • Function: Physical barrier that must not be compromised. If compromised (e.g., skin cut or inhalation of pathogens), the second line of defense activates.

Second Line of Defense

  • Definition: Activated when the first line is breached; involves nonspecific cells and proteins.

  • Key Components:

    • Cells: Neutrophils, macrophages, etc.

    • Response: Innate immune system action; not learned—present at birth.

    • Description: Responds to any pathogen with a general defense mechanism.

Third Line of Defense (Overview)

  • Definition: Specific immunity that is learned through previous exposures to pathogens.

  • Function: Body creates a learned response to previously encountered pathogens, resulting in less severe symptoms upon re-exposure.

Focus of Current Lecture

  • Concentration on the first and second lines of defense, details on the third line will come later.

Twenty Seconds to Switch Topics

  • Brief mention of a video that discusses the immune system's lines of defense (not shown).

Summary of First and Second Lines of Defense

  • First Line of Defense includes:

    • Physical barriers: skin, eyelashes, eyebrows.

    • Internal barriers: gut microbiome, acidic stomach, tears (wash away irritants).

  • Second Line of Defense includes:

    • Pre-existing defenses at birth.

    • Cellular components, proteins, inflammatory responses, and occasionally fever.

Example of Gut Microbiome

  • Importance of gut microbiome in maintaining homeostasis for GI health.

iClicker Question

  • Scenario: Study on patients prescribed antibiotics with two groups—one consuming probiotic, the other a placebo.

  • Hypothesis: Probiotic group will have enhanced recovery by maintaining gut microbiome.

  • Students participated in answering which line of defense this intervention targets:

    • Correct answer: A (first line of defense) focused on internal microbiome.

Study Design Question

  • Design Type: Randomized clinical trial (correct answer was C).

  • Details about study definitions:

    • In vitro study: conducted in a lab (incorrect).

    • Nonclinical intervention study: no intervention (incorrect).

    • Systematic review/meta-analysis: overarching examination of existing studies (not applicable).

Creative Learning Activity

  • Example of Miss Riley Brown who created a cell using a cookie to explain cellular functions and immunity.

Cellular Parts Explained:

  • Nucleus: Directs immune responses by regulating gene expression of cytokines and antibodies.

  • Ribosomes: Synthesize immune proteins.

  • Endoplasmic Reticulum: Folds and processes immune proteins, crucial for plasma cells.

  • Golgi Apparatus: Modifies, sorts and packages immune proteins like antibodies.

  • Mitochondria: Provides ATP for energy-intensive immune functions, regulates signaling and apoptosis.

  • Plasma Membrane: Contains receptors for antigen recognition and inter-cell communication, coordinating immune responses.

Phagocytosis

  • Definition: Cellular process where phagocytes engulf and digest particles or foreign bodies.

  • Key Cells Involved:

    • Macrophages: Consume bacteria and debris.

    • Neutrophils: First responders to infection.

    • Natural Killer Cells: Attack cancer cells by releasing perforin to target cell membranes.

Mechanism of Action for Natural Killer Cells

  • Release perforin, forming pores in target cells leading to cell lysis or bursting.

Complement System

  • Involves protein defense mechanism against bacteria, enhancing immune response.

    • Process Steps:

    1. Complement proteins puncture bacterium’s cell membrane.

    2. Bacterium can’t maintain homeostasis, leading to water influx and rupture.

  • Comprises over 20 proteins synthesized in the liver.

  • Activates in response to pathogens or antibody-antigen complexes, enhancing the immune response and inducing inflammation.

Inflammation Process

  • Responses to tissue damage including:

    • Widening of blood vessels, increased blood flow, redness and heat at the injury site.

    • Increased capillary permeability leading to swelling (seeping of fluid rich in defensive cells).

    • Physical Pain: Protective mechanism to prevent use of injured body parts.

R.I.C.E. Method for Injury Management

  • R: Rest, I: Ice, C: Compression, E: Elevation.

  • Controversy: Potential slowing of recovery process through this method by inhibiting necessary inflammatory processes.

Acute vs Chronic Inflammation

  • Acute Inflammation: Short-term response to injury, generally beneficial for healing.

  • Chronic Inflammation: Long-term state, associated with conditions like obesity and arthritis, can hinder healing and increase susceptibility to illness.

Fever Mechanism

  • Initiated when immune cells trigger pro-inflammatory cytokines, raising body's temperature set point via hypothalamus signaling.

  • Helps inhibit pathogen growth and enhances efficiency of immune cells.

iClicker True or False Question

  • Statement: Elevated neutrophil levels are likely seen in blood work after recovery from a cold.

    • Correct Answer: True, 98% of students answered accurately.

Discussion of Local Support and Defense System

Functional Cells (Parenchymal Cells)

  • Defined as cells performing specific functions in tissues and organs.

  • Examples include:

    • Hepatocytes: In liver for detoxification.

    • Myocytes: In skeletal muscle for movement.

    • Neurons: In the brain for signaling.

Support Cells (Stromal Cells)

  • Non-parenchymal cells providing structural support.

  • Examples:

    • Astrocytes: Support neural function at blood-brain barrier.

    • Fibroblasts: Create extracellular matrix, involved in weight regulation processes.

Pancreas: Functional and Stromal Views
Functional View of Pancreas

  • Focused on insulin and glucagon production:

    • Alpha Cells: Secrete glucagon to maintain blood glucose during fasting.

    • Beta Cells: Secrete insulin to lower blood sugar after meals.

Stromal View of Pancreas

  • Discusses cellular support roles.

  • Cholinergic Neurons: Produce acetylcholine, critical in Alzheimer’s disease, linked to memory function.

  • Macrophages: Involved in immune response.

Conclusion

  • The local support and defense system is continuously active—responsible for healing, normal tissue turnover, and cancer surveillance.

Closing Thank You

  • Acknowledgment to the students for participation in the lecture.