Biology · Year 12 · Non-Infectious Disease and Homeostasis · Term 4

Immune System Disorders: Allergies & Autoimmunity

Explore common immune system dysfunctions, including allergies and autoimmune diseases.

• ACARA Content Descriptions
• ACARA: Senior Secondary Biology Unit 3, Area of Study 2

About This Topic

Technologies and Disorders examines how modern medical technology can assist or replace failing body systems. Students study the mechanisms of hearing loss and vision impairment, and the technologies designed to treat them, such as cochlear implants, bone conduction implants, and bionic eyes. They also investigate the use of dialysis for kidney failure.

The curriculum requires students to evaluate the effectiveness and limitations of these technologies. In Australia, this includes looking at the pioneering work of Australian scientists (like Professor Graeme Clark and the cochlear implant). Students also consider the ethical and social implications of these technologies, including accessibility and the 'medicalisation' of disability. This topic is best taught through 'design challenges' where students must evaluate a technology's design against the biological function it is trying to replicate.

Key Questions

1. Explain the underlying mechanisms that lead to allergic reactions and anaphylaxis.
2. Analyze how autoimmune diseases result from a breakdown in immune tolerance.
3. Compare the causes and consequences of different types of autoimmune disorders.

Learning Objectives

• Analyze the immunological mechanisms underlying allergic reactions, including the roles of IgE antibodies and mast cells.
• Explain how a loss of self-tolerance leads to autoimmune diseases, citing specific examples.
• Compare and contrast the triggers, symptoms, and treatment strategies for common allergies and autoimmune disorders.
• Evaluate the effectiveness of current medical interventions for managing allergies and autoimmune conditions.

Before You Start

The Immune System: Cells and Responses

Why: Students need a foundational understanding of immune cells (like B cells, T cells, mast cells) and their normal functions to comprehend how these are dysregulated in disorders.

Homeostasis and Feedback Mechanisms

Why: Understanding how the body maintains stable internal conditions is crucial for grasping how immune tolerance breaks down and homeostasis is disrupted in autoimmune diseases.

Key Vocabulary

Allergen	A substance that triggers an allergic reaction in a susceptible individual, often a normally harmless substance like pollen or certain foods.
Anaphylaxis	A severe, potentially life-threatening allergic reaction that can occur rapidly and affect multiple body systems, requiring immediate medical attention.
Autoimmunity	A condition where the immune system mistakenly attacks the body's own healthy tissues, perceiving them as foreign invaders.
Immune Tolerance	The ability of the immune system to recognize and not attack the body's own cells and tissues, a critical process for preventing autoimmunity.
Epitope	The specific part of an antigen that is recognized by an antibody or T cell receptor during an immune response.

Watch Out for These Misconceptions

Common Misconception

Cochlear implants 'restore' normal hearing.

What to Teach Instead

Cochlear implants provide a digital representation of sound that the brain must learn to interpret; it is not the same as natural hearing. Using 'simulated audio' clips of what a cochlear implant sounds like helps students understand the limitations of the technology.

Common Misconception

Dialysis is a permanent cure for kidney failure.

What to Teach Instead

Dialysis is a life-sustaining treatment that performs some kidney functions, but it is not a cure and requires frequent, long sessions. A 'day in the life' scheduling activity helps students realize the significant time and health burden dialysis places on patients.

Active Learning Ideas

Inquiry Circle: The Bionic Eye Design

Students are given a diagram of the human eye and a 'broken' component (e.g., a damaged retina). They must research how a bionic eye works and draw a diagram showing how the technology bypasses the damaged part to send signals to the brain, then present their 'fix' to the class.

50 min·Small Groups

Formal Debate: The Cochlear Controversy

Students research the 'Deaf Culture' perspective on cochlear implants versus the medical perspective. They hold a structured debate on whether these technologies should be framed as 'cures' or 'tools,' focusing on the social and cultural impact on the Deaf community in Australia.

45 min·Whole Class

Stations Rotation: Dialysis vs. The Kidney

Set up stations comparing a healthy kidney's filtration to a dialysis machine. Students use a 'filtration' model (e.g., sieves and beads of different sizes) to see what dialysis can and cannot remove from the blood, then list the lifestyle limitations of being on dialysis.

55 min·Small Groups

Real-World Connections

• Allergists at hospitals like The Alfred in Melbourne diagnose and manage conditions ranging from seasonal hay fever to severe food allergies, prescribing antihistamines or emergency epinephrine auto-injectors.
• Rheumatologists, specialists in autoimmune diseases, work at clinics to treat patients with conditions such as rheumatoid arthritis or lupus, often coordinating care with physiotherapists and dietitians.
• Researchers at the Garvan Institute of Medical Research are investigating the genetic and environmental factors that contribute to the development of autoimmune diseases, aiming to find new therapeutic targets.

Assessment Ideas

Discussion Prompt

Pose the question: 'Imagine a patient presents with symptoms of both a severe allergy and an autoimmune disorder. What are the key differences in how you would approach diagnosis and treatment, considering the underlying immune system malfunction?' Facilitate a class discussion where students articulate these differences.

Quick Check

Provide students with short case studies, each describing a patient with either an allergic reaction or an autoimmune disease. Ask students to identify the condition, list 2-3 key symptoms, and propose one potential treatment strategy based on the underlying immune mechanism.

Peer Assessment

Students create a Venn diagram comparing and contrasting allergies and autoimmune diseases. They then exchange diagrams with a partner. Each partner checks for accuracy and completeness, providing written feedback on at least two points of comparison or contrast.

Frequently Asked Questions

How does a cochlear implant work?

A cochlear implant bypasses damaged hair cells in the inner ear. An external microphone picks up sound, which is converted into electrical signals. These signals are sent to an electrode array implanted in the cochlea, which directly stimulates the auditory nerve. The brain then interprets these electrical impulses as sound.

What are the limitations of dialysis?

While dialysis filters waste and excess fluid from the blood, it cannot perform the hormonal functions of the kidney, such as producing erythropoietin for red blood cell production. It is also time-consuming, usually requiring several hours three times a week, and does not filter as continuously or efficiently as a healthy kidney.

How can active learning help students understand medical technologies?

Medical technologies are often 'black boxes' to students. Active learning strategies like 'designing a bionic limb' or 'simulating sensory loss' force students to engage with the underlying biology. When they have to figure out exactly where a signal is blocked and how a machine can bridge that gap, they gain a much deeper appreciation for both the ingenuity of the technology and the complexity of the human body.

What is the difference between conductive and sensorineural hearing loss?

Conductive hearing loss occurs when sound cannot pass through the outer or middle ear (e.g., due to a blockage or earwax). Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea) or the auditory nerve. Different technologies, like hearing aids vs. cochlear implants, are required depending on the type of loss.