Study Guidance for Host Defenses (Immunology) – Microbiology

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

Background

Topic: Immune System Overview

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 first line of defense, present from birth, non-specific, and immediate.

• Adaptive Immunity: Develops after exposure to antigens, specific, and has memory.

• Host Response: The way the body reacts to pathogens, can be innate or adaptive.

Step-by-Step Guidance

1. Start by defining innate immunity—describe its characteristics, speed, specificity, and examples (e.g., skin, phagocytes).

2. Define adaptive immunity—explain how it differs from innate immunity, its specificity, memory, and examples (e.g., B and T lymphocytes).

3. List examples of host responses (e.g., inflammation, antibody production) and determine if each is innate or adaptive based on your definitions.

4. Think about how the two systems interact and overlap in defending 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: Hematopoiesis and Immune Cell Function

This question tests your knowledge of the origin (lineage) and roles of various immune cells.

Key Terms

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

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

• Function: The main role each cell type plays in immunity (e.g., phagocytosis, antigen presentation, cytotoxicity).

Step-by-Step Guidance

1. List each cell type under its correct lineage (myeloid or lymphoid).

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

3. Note any unique features or roles (e.g., dendritic cells as antigen-presenting cells, NK cells as part of innate immunity).

4. Compare and contrast the general roles of myeloid vs. lymphoid cells in host defense.

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Q3. Define Cytokine, Interleukin, and Chemokine.

Background

Topic: Immune Signaling Molecules

This question focuses on the definitions and roles of key signaling molecules in the immune system.

Key Terms

• Cytokine: Broad category of small proteins important in cell signaling.

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

• Chemokine: A subset of cytokines that direct cell movement (chemotaxis).

Step-by-Step Guidance

1. Start by defining cytokine as a general term for immune signaling proteins.

2. Define interleukin and explain how it is a specific type of cytokine, often numbered (e.g., IL-2).

3. Define chemokine and describe its role in attracting immune cells to sites of infection or inflammation.

4. Think about examples of each and how they interact in immune responses.

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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 tests your understanding of how physical and chemical barriers protect the host from infection.

Key Terms

• Skin: Outermost barrier preventing pathogen entry.

• Mucous membranes: Linings of body cavities that trap and remove microbes.

• Innate immunity: Non-specific, immediate defense mechanisms.

Step-by-Step Guidance

1. Describe how the skin acts as a physical and chemical barrier (e.g., keratin, acidic pH).

2. Explain the role of mucous membranes in trapping pathogens and facilitating their removal (e.g., cilia, mucus).

3. Mention additional factors like antimicrobial peptides and enzymes (e.g., lysozyme in tears/saliva).

4. Relate these barriers to the concept of innate immunity (non-specific, always present).

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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 knowledge of the process of phagocytosis, the role of PRRs and opsonization, and microbial evasion strategies.

Key Terms and Concepts

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

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

• Opsonization: Coating of microbes to enhance phagocytosis.

• Immune Evasion: Strategies used by pathogens to avoid destruction.

Step-by-Step Guidance

1. List the six steps of phagocytosis (e.g., chemotaxis, adherence, ingestion, phagosome formation, fusion with lysosome, digestion).

2. Explain how PRRs on phagocytes recognize pathogen-associated molecular patterns (PAMPs) to initiate adherence.

3. Describe how opsonization (e.g., by antibodies or complement) enhances adherence and uptake.

4. Discuss how Leishmania donovani and other microbes evade phagocytosis (e.g., inhibiting phagolysosome fusion, resisting digestion).

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