Immune Response AS Biology Pearson Edexcel

Immune system

1. Immune Response Teaching Pack
This teaching pack contains a comprehensive study guide, student worksheets,
and detailed memoranda (mark schemes) . It is designed for Advanced Level (AL)
Biology students but is structured so teachers can adapt and resell as a complete
classroom resource.
Part 1: Study Guide (Comprehensive Notes)
1. Humoral Response (Antibody-Mediated Immunity)
Definition: The aspect of immunity that involves B lymphocytes and the
production of antibodies in response to antigens.
Steps in Humoral Response:
1.Antigen Presentation: Macrophages and dendritic cells phagocytose
pathogens and present antigens on their surface using MHC II
molecules.
2.Activation of Helper T Cells (Th cells): These recognize the antigen-
MHC II complex and become activated.
3.Clonal Selection of B Cells: Specific B cells with complementary
receptors bind to the antigen. Activated Th cells release cytokines
(interleukins) to stimulate these B cells.
4.Clonal Expansion and Differentiation:
Plasma Cells: Produce large quantities of antibodies specific to
the antigen.
Memory B Cells: Remain in circulation for faster secondary
responses.
Functions of Antibodies:
oNeutralization of toxins and viruses.
oOpsonization: Marking pathogens for phagocytosis.
oAgglutination: Clumping of pathogens for easier engulfing.
oComplement activation: Initiating the complement cascade leading to
pathogen lysis.
Example Diseases: Bacterial infections like Salmonella, diphtheria.
2. Cell-Mediated Response (T Cell-Mediated Immunity)

2. Definition: Immunity primarily involving T lymphocytes against infected or
abnormal cells.
Steps in Cell-Mediated Response:
1.Antigen Presentation by Infected Cells: Pathogen-infected cells
display antigens with MHC I molecules.
2.Activation of Cytotoxic T Cells (Tc cells): Helper T cells release
cytokines that activate cytotoxic T cells.
3.Clonal Expansion: Tc cells divide into active killer T cells and memory
T cells.
4.Destruction of Infected Cells: Killer T cells release perforin, which
forms pores in infected cell membranes, leading to apoptosis
(programmed cell death).
Key Roles:
oEliminating virus-infected cells.
oDestroying cancerous cells.
Example Diseases: Viral infections like measles, influenza, and HIV.
3. Immunity
Types of Immunity:
oNatural Immunity:
Active: Following infection (memory cells produced).
Passive: Maternal antibodies through placenta or breast milk.
oArtificial Immunity:
Active: Vaccination with attenuated or inactivated pathogens.
Passive: Injection of pre-formed antibodies (antiserum).
Primary vs. Secondary Response:
oPrimary: Slower, lower concentration of antibodies.
oSecondary: Faster, stronger due to memory cells.
Autoimmune Diseases: Conditions where the immune system attacks ‘self’
cells, e.g. Type 1 diabetes, multiple sclerosis.
4. Antibiotics
Definition: Substances produced by microorganisms (or synthetically) that
inhibit or kill other microbes, particularly bacteria.
Types:
oBactericidal: Kill bacteria (e.g. penicillin).
oBacteriostatic: Inhibit growth and reproduction (e.g. tetracycline).

3. Modes of Action:
oInhibit cell wall synthesis.
oDisrupt protein synthesis by binding to ribosomes.
oInhibit DNA/RNA replication.
Limitations:
oIneffective against viruses (since viruses lack cell structures like
ribosomes or walls).
oAntibiotic resistance due to overuse and misuse.
Examples of Resistance: MRSA, drug-resistant TB.
Part 2: Worksheets (Student Activities)
Worksheet 1: Humoral Response
1.Describe the role of plasma cells in immunity. (2 marks)
2.Draw and label a flowchart showing the stages of the humoral response. (6
marks)
3.Explain how antibodies help prevent infection. Give two examples. (4 marks)
Worksheet 2: Cell-Mediated Response
1.What type of pathogen is the cell-mediated response especially effective
against? (1 mark)
2.Explain how cytotoxic T cells kill infected cells. (4 marks)
3.Compare the role of memory B cells and memory T cells. (4 marks)
Worksheet 3: Immunity
1.Differentiate between active and passive immunity with examples. (4 marks)
2.Explain why a secondary immune response is faster and stronger. (3 marks)
3.Case Study: A child receives the polio vaccine. Identify the type of immunity
and explain how protection is achieved. (4 marks)
Worksheet 4: Antibiotics
1.Explain why antibiotics are ineffective against viruses. (2 marks)
2.Compare bacteriostatic and bactericidal antibiotics. (3 marks)
3.Case Study: MRSA is resistant to many antibiotics. Suggest reasons for this
resistance and ways to reduce its spread. (6 marks)

4. Part 3: Memoranda (Answer Keys)
Worksheet 1 Answers
1.Plasma cells produce large numbers of antibodies specific to an antigen. (2)
2.Flowchart should include: antigen presentation activation of helper T cells
→
activation of B cells clonal expansion plasma/memory cells
→ → → →
antibody production. (6)
3.Antibodies neutralize toxins, opsonize pathogens, cause agglutination, or
activate complement. (Any 2 with explanation, 4)
Worksheet 2 Answers
1.Viruses and intracellular pathogens. (1)
2.Tc cells release perforin, forming pores infected cell lyses/apoptosis. (4)
→
3.Memory B cells produce antibodies rapidly on reinfection; memory T cells
rapidly activate cytotoxic T cells. (4)
Worksheet 3 Answers
1.Active: body produces antibodies/memory cells (e.g. infection, vaccine).
Passive: ready-made antibodies (e.g. mother’s milk, antiserum). (4)
2.Memory cells allow rapid recognition and production of antibodies/T cells.
(3)
3.Artificial active immunity; attenuated pathogen triggers immune response
and memory cell formation. (4)
Worksheet 4 Answers
1.Viruses lack cell structures like cell walls/ribosomes; antibiotics target these.
(2)
2.Bacteriostatic inhibit growth; bactericidal kill bacteria. (3)
3.Resistance from overuse, mutations, gene transfer; prevention: controlled
prescription, full course completion, hygiene. (6)
Teacher Notes
Pedagogy Tips:
oUse diagrams and flowcharts to show processes.
oEncourage active recall with past exam questions.
oLink immunity concepts to current health issues (e.g. COVID-19
vaccines, antibiotic resistance).

5. Extension Ideas:
oDebate: “Should antibiotics be available without prescription?”
oResearch project on latest vaccine developments.
✅ This pack now includes in-depth explanations, student worksheets, and
answer keys, making it classroom-ready and resellable to teachers.