Practice Questions on Immunity for OCR A Level Biology: An In-Depth Guide

Introduction to Immunology in OCR A Level Biology

Biology students preparing for the OCR A Level Biology exam will encounter a range of challenging questions related to the immune system. This guide offers a comprehensive overview of some essential practice questions that will help you deepen your understanding and improve your performance in the exam.

Immunity Practice Questions

1. Complement System Activation

Discuss the fundamental difference between the way the complement system is activated by the alternative pathway and the way it is activated by the lectin activation pathway.

2. Innate Immune System Activation

Explain how macrophages and natural killer cells ‘tell friend from foe’ i.e., how they select their targets for activation.

3. Innate Immune Response to Bacterial Invasion

Imagine a scenario where a splinter has punctured your big toe and Gram-negative bacteria producing LPS have invaded the surrounding tissues. Sketch the likely sequence of events in which the various players of the innate system team deal with this bacterial invasion.

4. Innate System Protection Against Virus Attack

Discuss the ways the innate system can protect against a viral infection and provide examples of how these mechanisms work together.

5. Innate Immune System Cooperation

Provide examples of cooperation between the players of the innate system team and explain why this cooperation is critical for effective immunity.

B Cell and Antibody Mechanisms

1. Clonal Selection Principle

B cells are produced according to the principle of clonal selection. Explain what this means and how it contributes to the immune response.

2. T Cell-Dependent B Cell Activation

Describe what happens during T cell-dependent activation of B cells and what role T cells play in this process.

3. T Cell-Independent B Cell Activation

Explain how B cells can be activated without T cell help and provide an example of a pathogen that elicits a T cell-independent antibody response.

4. Fail-Safe Systems in B Cell Activation

Describe the fail-safe systems that are involved in B cell activation and why they are crucial for immune function.

5. Antibody Types

List and explain the main attributes of IgM, IgG, IgA, and IgE antibodies, including their functions and importance in different immune responses.

6. Class Switching and Somatic Hypermutation

Discuss why class switching and somatic hypermutation are important for the immune system, producing B cells that are better equipped to defend against invaders.

Showcasing Antigen Presentation in Immune Responses

1. Class I MHC Antigen Presentation

Explain several reasons why antigen presentation by class I MHC molecules is integral to the adaptive immune response.

2. Class II MHC Antigen Presentation

Discuss why antigen presentation by class II MHC molecules is advantageous and explain the different roles played by activated dendritic cells, macrophages, and B cells in antigen presentation during an infection.

3. Dendritic Cell Stages of Activity

Describe the three stages of dendritic cell activity (samplers, travelers, presenters) and the functions performed during each stage.

4. Efficiency of Antigen Presentation by MHC Molecules

Discuss the factors that influence the efficiency of antigen presentation by class I and class II MHC molecules.

T-Cell Activation Mechanisms

1. Co-Receptors and Costimulation

Define and give examples of co-receptors and costimulation, explaining their importance in T cell activation.

2. Cellular Adhesion Molecules and T-Cell Activation

Discuss the role of cellular adhesion molecules in T cell activation and explain why these molecules are essential, despite appearing to slow the process.

3. Dendritic Cell and Helper T-Cell Interaction

Describe what happens during the “dance” between dendritic cells and helper T cells and the importance of this interaction.

4. Activation Cascade for Adaptive Immunity

Trace the steps in the activation cascade that begins with a Gram-negative bacterium carrying LPS entering a wound and ends with the production of antibodies that can recognize the bacterium.

5. Fail-Safe Mechanisms in Adaptive Immune System

Provide examples of fail-safe mechanisms that prevent the inappropriate activation of the adaptive immune system and explain their importance.

T-Cells at Work

1. Helper T Cell Cytokine Production

Explain how a helper T cell determines which cytokine profile to produce and how it “calls the plays” for B cells.

2. Helper T Cell Roles in Innate Immune System Activation

Discuss how a helper T cell orchestrates the actions of innate system players like macrophages and NK cells.

3. Cytokine Range and Immune System Function

Explain why the limited range of cytokines is advantageous for the immune system and how it ensures a targeted response.

4. Types of T Cell Death

Define the difference between death by necrosis and death by apoptosis and explain their significance in the immune response.

T Cell Self-Tolerance and MHC Restriction

1. Importance of T Cell Self-Tolerance Testing

Explain why T cells must be tested to ensure they can recognize self MHC molecules and discuss why the current method is necessary.

2. Functional Definition of Self for T Cells

Discuss what T cells consider to be self peptides and the challenges they face in satisfying both self and MHC restrictions simultaneously.

3. Mechanisms for Maintaining T Cell Self-Tolerance Post-Thymus

Describe the mechanisms needed to tolerize T cells once they leave the thymus and explain why the traffic pattern of virgin T cells plays a role in maintaining tolerance of self.

4. Importance of B Cell Self-Tolerance Testing

Explain why B cells are also screened for tolerance of self and the significance of this screening.

5. Types of Dendritic Cells and Their Functions

Provide an overview of the four types of dendritic cells (plasmacytoid DCs, antigen-presenting DCs, follicular DCs, and thymic DCs) and their functions.

Intestinal Immune System

1. Differences Between Intestinal and Systemic Immune Systems

Discuss several ways in which the intestinal immune system differs from the systemic immune system that protects other areas of the body.

2. Special Features in Intestinal Immune Tissues

Explain the special features of the immune system in the tissues surrounding the intestines that help avoid an overreaction to commensal bacteria.

3. IgA Antibodies: ‘Passive’ Antibodies

Define why IgA antibodies are called ‘passive’ and provide examples of their importance in the gut immune system.

4. Inducible Regulatory T Cells (iTregs) in Intestine

Describe the function and importance of inducible regulatory T cells in the gut immune system.

5. Designing an Ideal Intestinal Immune System

If designing the intestinal immune system, what key features would you incorporate to ensure it can effectively differentiate between friends and foes?

Autoimmunity

1. Mast Cell Degranulation During Allergic Reactions

Describe the events that lead to the degranulation of mast cells during an allergic reaction.

2. Factors Contributing to Allergy Development

Discuss why some people have allergies while others do not and explore the factors that contribute to the development of allergies.

3. Initiating Autoimmunity

Explain what events likely are required to initiate autoimmunity and delve into the complexities of this process.

4. Proof of Microbial Infection's Insufficiency

Provide evidence that solely a microbial infection is not sufficient to cause autoimmune disease and explore the underlying mechanisms.