Study Guide: Host Defenses and Immunity (Chapters 15 & 16) – Microbiology

Q1. Define innate and adaptive immunity and characterize host responses as innate or adaptive.

Background

Topic: Types of Immunity

This question tests your understanding of the two main branches of the immune system: innate (nonspecific) and adaptive (specific) immunity, and your ability to classify immune responses accordingly.

Key Terms

• Innate Immunity: The body's first line of defense, present from birth, non-specific, and immediate.

• Adaptive Immunity: A specific immune response that develops over time and involves memory.

Step-by-Step Guidance

1. Start by defining innate immunity—think about its characteristics, speed, and specificity.

2. Next, define adaptive immunity—focus on how it differs from innate immunity in terms of specificity and memory.

3. List examples of host responses (e.g., skin barrier, antibody production) and decide if each is innate or adaptive, explaining your reasoning.

4. Consider how these two systems interact to protect the host.

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Q2. Differentiate among the following cell types in terms of lineage and function: Myeloid cells (Mast cells, Basophils, Eosinophils, Neutrophils, Monocytes/Macrophages, Dendritic cells) and Lymphoid cells (B cells, T cells, Natural killer cells).

Background

Topic: Immune Cell Lineages and Functions

This question assesses your knowledge of the major immune cell types, their origins (myeloid vs. lymphoid), and their roles in immunity.

Key Terms

• Myeloid lineage: Cells derived from myeloid progenitors (e.g., granulocytes, monocytes).

• Lymphoid lineage: Cells derived from lymphoid progenitors (e.g., B cells, T cells, NK cells).

Step-by-Step Guidance

1. List each cell type and identify whether it is of myeloid or lymphoid origin.

2. For each cell, briefly describe its main function in the immune response (e.g., phagocytosis, antibody production, cytotoxicity).

3. Note any unique features or markers that help distinguish these cells.

4. Consider how these cells interact within the immune system.

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Q3. Define Cytokine, Interleukin, and Chemokine.

Background

Topic: Immune Signaling Molecules

This question tests your understanding of the different types of signaling molecules that mediate immune responses.

Key Terms

• Cytokine: General term for small proteins important in cell signaling in the immune system.

• Interleukin: A type of cytokine, often involved in communication between leukocytes.

• Chemokine: A subset of cytokines that specifically induce chemotaxis in nearby cells.

Step-by-Step Guidance

1. Define the term cytokine and its general role in immunity.

2. Explain what interleukins are and how they fit within the broader category of cytokines.

3. Describe chemokines and their specific function in immune cell movement.

4. Provide examples of each, if possible.

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Q4. Explain the function of skin and mucus membranes as part of the innate immune system.

Background

Topic: Physical Barriers in Innate Immunity

This question focuses on the role of physical and chemical barriers in preventing pathogen entry.

Key Terms

• Skin: The body's largest organ, acts as a physical barrier.

• Mucous membranes: Line body cavities and secrete mucus to trap pathogens.

Step-by-Step Guidance

1. Describe how the skin acts as a barrier to infection (structure, secretions, etc.).

2. Explain the role of mucous membranes and how they trap and remove pathogens.

3. Mention any chemical defenses associated with these barriers (e.g., lysozyme, acidic pH).

4. Discuss how these barriers are part of the innate, not adaptive, immune system.

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Q5. Outline the six steps of phagocytosis and discuss the role of pattern recognition receptors (PRRs) and opsonization in promoting adherence and the mechanisms certain microorganisms have of avoiding phagocytosis, in particular Leishmania donovani.

Background

Topic: Phagocytosis and Immune Evasion

This question tests your understanding of the process of phagocytosis, the role of PRRs and opsonization, and microbial evasion strategies.

Key Terms

• Phagocytosis: The process by which cells engulf and digest pathogens.

• Pattern Recognition Receptors (PRRs): Receptors that recognize common microbial patterns.

• Opsonization: The process of marking pathogens for phagocytosis.

Step-by-Step Guidance

1. List the six steps of phagocytosis in order (e.g., chemotaxis, adherence, ingestion, etc.).

2. Explain how PRRs help phagocytes recognize pathogens.

3. Describe how opsonization enhances adherence of pathogens to phagocytes.

4. Discuss at least one mechanism by which Leishmania donovani avoids phagocytosis.

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