CORE Immunology
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Questions and Answers

What is the primary function of B cells in adaptive immunity?

  • Produce cytokines to activate immune responses
  • Kill infected host cells
  • Produce antibodies (correct)
  • Process antigens for T cell recognition

Which statement correctly distinguishes between cytotoxic T cells and NK cells?

  • NK cells require antigen recognition to act.
  • Cytotoxic T cells require MHC presentation for activation. (correct)
  • NK cells target only infected cells with specific antigens.
  • Cytotoxic T cells respond more quickly than NK cells.

What must happen for T cells to recognize an antigen?

  • The antigen must bind directly to T cell receptors.
  • The antigen must be processed and presented by B cells.
  • The antigen must be neutralized by antibodies first.
  • The antigen must be presented on MHC molecules. (correct)

What characterizes the MHC Class 1 pathway?

<p>It is found on the surface of almost all body cells. (A)</p> Signup and view all the answers

How do T Cell Receptors (TCR) recognize antigens?

<p>By binding to MHC molecules displaying processed antigens. (D)</p> Signup and view all the answers

Which cells are primarily involved in phagocytosis?

<p>Macrophages (C)</p> Signup and view all the answers

What role does CD16 play in NK cell activation?

<p>Binds to antibodies for ADCC (C)</p> Signup and view all the answers

What occurs when MHC class I molecules are absent from cells?

<p>NK cells activate and destroy the target cell (C)</p> Signup and view all the answers

What are Pathogen Associated Molecular Patterns (PAMPs)?

<p>Structures shared by many pathogens (B)</p> Signup and view all the answers

What is the primary function of macrophages?

<p>To engulf bacteria and present antigens (A)</p> Signup and view all the answers

Which immune cell is primarily responsible for attacking parasites?

<p>Eosinophils (B)</p> Signup and view all the answers

Which receptors recognize PAMPs in innate immunity?

<p>Toll-like receptors (TLRs) (C)</p> Signup and view all the answers

How do neutrophils respond to pathogens?

<p>By phagocytosing and activating bactericidal mechanisms (B)</p> Signup and view all the answers

What is the primary function of immature dendritic cells?

<p>Activation of adaptive immunity (B)</p> Signup and view all the answers

What is the role of Natural Killer (NK) cells in the immune response?

<p>To kill host cells that are infected with viruses (A)</p> Signup and view all the answers

What do lysosomes do during phagocytosis?

<p>Fuse with phagosome and break down the microbe (C)</p> Signup and view all the answers

Which receptors are specifically mentioned for their role in NK cell activation?

<p>Killer Immunoglobulin-like receptors (KIR) (A)</p> Signup and view all the answers

Opsonization primarily facilitates which process in the immune response?

<p>Enhanced phagocytosis of difficult-to-capture microbes (A)</p> Signup and view all the answers

What type of immune response do PRRs promote upon detecting PAMPs?

<p>Aiding in phagocytosis (B)</p> Signup and view all the answers

Which cell type is most abundant in the white blood cell population?

<p>Neutrophils (D)</p> Signup and view all the answers

Mast cells play a crucial role in which type of immune response?

<p>Allergic responses and inflammation (B)</p> Signup and view all the answers

What is the primary purpose of inflammation?

<p>To promote tissue repair (A)</p> Signup and view all the answers

Which suffix is used to denote inflammation in medical terminology?

<p>-itis (A)</p> Signup and view all the answers

Which of the following is NOT a symptom of inflammation?

<p>Fever (B)</p> Signup and view all the answers

What initiates the recruitment of neutrophils during inflammation?

<p>TNF alpha and IL-1 activation (C)</p> Signup and view all the answers

Which step involves the reduction of blood velocity in inflammation?

<p>Vasodilation (D)</p> Signup and view all the answers

What is the role of E-selectin in neutrophil recruitment?

<p>Facilitates neutrophil rolling (D)</p> Signup and view all the answers

In adaptive immunology, what is the initial response of a lymphocyte to an antigen called?

<p>Activation (A)</p> Signup and view all the answers

Which phase of adaptive immunity involves the division of activated B or T cells?

<p>Clonal expansion (D)</p> Signup and view all the answers

Which chemokines are involved in the recruitment of monocytes?

<p>CCL2 and CCL7 (C)</p> Signup and view all the answers

What happens to T and B cells after the immune response is completed?

<p>They undergo apoptosis (A)</p> Signup and view all the answers

What role do Danger Associated Molecular Patterns (DAMPs) primarily play in the immune system?

<p>They activate the immune system during cell injury. (C)</p> Signup and view all the answers

What does C3b do in the complement system?

<p>Attaches to microbe surfaces for phagocytosis. (B)</p> Signup and view all the answers

Which of the following cytokines is considered pro-inflammatory?

<p>IL-1 (D)</p> Signup and view all the answers

What is a primary function of the complement system?

<p>To promote inflammation and opsonization. (D)</p> Signup and view all the answers

Which of the following describes the function of C5a in the immune response?

<p>It promotes vasodilation and increases vascular permeability. (D)</p> Signup and view all the answers

What characterizes the membrane attack complex formation?

<p>It involves binding fragments that lead to cell lysis. (D)</p> Signup and view all the answers

Which statement about cytokines is true?

<p>They have autocrine, paracrine, and endocrine actions. (C)</p> Signup and view all the answers

What type of proteins are primarily found in the complement system?

<p>Soluble proteins (A)</p> Signup and view all the answers

Which of the following best describes cytokine networks?

<p>They consist of complex interactions between multiple cytokines. (A)</p> Signup and view all the answers

What is a key characteristic of proteases in the complement system?

<p>They can cleave other proteins to activate complement components. (B)</p> Signup and view all the answers

Flashcards

Barrier Function

The first line of defense against pathogens, preventing their entry into the body. It includes physical barriers like skin and mucous membranes, as well as chemical barriers like stomach acid.

Innate Immunity

The body's non-specific defense system that responds rapidly to all pathogens. It involves cells like macrophages and neutrophils that engulf invaders, and chemical signals that trigger inflammation.

Adaptive Immunity

The body's specific defense system that targets particular pathogens and remembers them for future encounters. It involves cells like T cells and B cells that recognize and destroy specific invaders.

Macrophages

Immune cells that patrol tissues, engulf bacteria through phagocytosis, clean up debris, and present antigens to other immune cells.

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Neutrophils

The most abundant white blood cells, engulf bacteria by phagocytosis and activate bactericidal mechanisms. They are recruited to sites of infection.

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Phagocytosis

The process by which cells engulf and internalize particles, like bacteria, by surrounding them with their cell membrane.

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Opsonisation

A process where microbes are coated with proteins, making them easier for phagocytes to capture and engulf. It enhances the efficiency of phagocytosis.

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B cells

White blood cells that produce antibodies, which are proteins that bind to and neutralize pathogens.

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Helper T cells

A type of T cell that helps other immune cells, like B cells and cytotoxic T cells, to mount an effective immune response.

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Cytotoxic T cells

A type of T cell that directly kills infected host cells. They recognize specific antigens presented on MHC class 1 molecules.

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MHC Class I Pathway

A process where cells present antigens from inside the cell (e.g., viral proteins) on MHC Class I molecules to cytotoxic T cells.

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MHC Class II Pathway

A process where certain immune cells present antigens from outside the cell (e.g., bacterial proteins) on MHC Class II molecules to helper T cells.

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Which cells use phagocytosis?

Macrophages, neutrophils, eosinophils, basophils, and immature dendritic cells all use phagocytosis.

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Phagocytosis steps

  1. Microbe binds to phagocyte receptors.
  2. Phagocyte membrane surrounds the microbe.
  3. Microbe is ingested into a phagosome.
  4. Lysosomes fuse with phagosome creating a phagolysosome.
  5. Lysosomes break down the microbe.
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NK cell activation (ADCC)

Natural Killer (NK) cells are activated by antibodies bound to target cells. This process is called antibody-dependent cell cytotoxicity (ADCC).

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NK cell activation (MHC Class I)

NK cells are activated when they detect the absence of MHC Class I on target cells. This indicates the cell may be infected or cancerous.

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Innate vs. Adaptive Immunity

Innate immunity is the first line of defense, using generic receptors and mechanisms to fight pathogens. Adaptive immunity is more specific, developing antibodies targeting particular invaders.

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PAMPs

Pathogen-Associated Molecular Patterns (PAMPs) are structures shared by most pathogenic bacteria and some viruses. These are recognized by innate immune cells.

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PRRs

Pattern Recognition Receptors (PRRs) are receptors on innate immune cells that recognize PAMPs. They are found on cell surfaces, endosomal membranes, and cytoplasm.

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Toll-Like Receptors (TLRs)

A category of PRRs that recognize specific PAMPs. There are multiple types of TLRs in humans (TLR 1-TLR 9).

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Complement

A group of soluble proteins in the blood that help the immune system fight pathogens. It promotes phagocytosis, inflammation, and direct killing.

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Opsonization (Complement)

The process where C3b from complement attaches to a pathogen's surface and is then recognized by CR1 receptors on phagocytes, leading to phagocytosis and destruction.

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Membrane Attack Complex (MAC)

A complex of complement proteins (C5b, C6, C7, C8, C9) that forms a pore in the pathogen's membrane, causing lysis.

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C3a and C5a (Complement)

Fragments released during complement activation responsible for promoting inflammation by causing vasodilation and increased vascular permeability. C5a also acts as a chemotactic factor.

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Cytokines

Soluble proteins made by various cells that can act on the cell that produced them (autocrine), nearby cells (paracrine), or distant cells (endocrine).

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Pro-inflammatory Cytokines

Cytokines that promote inflammation, such as IL-1, IL-6, and TNF-alpha. They are essential for fighting infection.

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Anti-inflammatory Cytokines

Cytokines that suppress inflammation, such as TGF-beta and IL-10. They help to prevent excessive inflammation and tissue damage.

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Chemotactic Cytokines

Cytokines that attract immune cells to the site of infection, such as CCL3 and CXCL1. This helps to concentrate immune cells where they are needed.

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Cytokine Networks

Complex interactions between different types of cytokines, influencing a range of immune responses.

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Inflammation

A localized response to injury or infection that aims to eliminate the cause, wall off damage, and promote healing.

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Suffix -itis

A suffix often used in medical terminology to indicate inflammation. For example, 'appendicitis' refers to inflammation of the appendix.

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What are the steps of inflammation?

  1. Detection of PAMPs or DAMPs (signals of danger). 2. Release of mediators causing vasodilation, increased permeability, and immune cell recruitment. 3. Elimination of the trigger. 4. Tissue repair.
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Vasodilation

The widening of blood vessels, leading to increased blood flow.

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Increased Vascular Permeability

The ability of blood vessels to allow more fluids and cells to leak out into surrounding tissues.

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Neutrophil rolling

The first step in neutrophil recruitment, where they loosely bind to the blood vessel wall and roll along it.

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Neutrophil Adhesion

The firm attachment of neutrophils to the blood vessel wall, where they stick and prepare to enter the tissues.

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Monocyte Recruitment

The recruitment of monocytes, which arrive after neutrophils to support the inflammatory response.

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Antigen

A molecule that triggers an immune response by being recognized by lymphocytes or antibodies.

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Naive Lymphocytes

Mature B or T cells that haven't encountered an antigen yet. They are ready and waiting to respond.

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Study Notes

Introduction to Immunology

  • Immunology is the study of the immune system
  • The immune system defends the body against infection, tumours, and tissue damage
  • It also plays a role in tissue repair and inflammation
  • The immune system has mechanisms to recognize and respond to foreign substances, including microbes, grafts, and introduced proteins.

Roles of the Immune System

  • Defense against infections: vaccinations boost immune defenses against infections
  • Defense against tumours: Immunotherapy for cancer
  • Control of tissue regeneration & scarring: Repair of damaged tissues
  • Injuring cells and inducing pathologic inflammation: Immune responses cause allergic reactions and inflammation
  • Recognizing and responding to tissue grafts and newly introduced proteins: Barriers to transplantation and gene therapy

Problems with the Immune System

  • Immunodeficiency: Failure to respond to a substance/infection (e.g., malnutrition);
  • Allergy: Inappropriate response to foreign substances.
  • Autoimmune disorders: Inappropriate response to self leading to body attacking itself (e.g. lupus).
  • Transplant rejection: Appropriate but unwanted response to foreign substances.
  • Cancer: Altered self causing evasion of immune system.
  • Pregnancy: Causes toleration of non-self.

Physical & Chemical Barriers

  • Skin: Epithelial cells with tight junctions, fatty acids, low pH, enzymes, defensins, cathelicidin.
  • Gut: Longitudinal flow, enzymes (pepsin), alpha-defensins (cryptdins), normal microbiota.
  • Lungs: Longitudinal flow of air/fluid, mucus movement by cilia, pulmonary surfactant, beta-defensins.
  • Eyes/nose/oral cavity: Enzymes in tears and saliva (lysozyme), beta-defensins, histatins, cathelicidin.

Immune Responses

  • Innate Defenses: Immediate response before infection occurs. Recognizes infection via receptors that recognize common pathogen structures
  • Adaptive Response: Slow response stimulated by specific pathogens, reacts to a multitude of structures. It has a memory and is very specific.

Innate and Adaptive Immunity

Feature Innate Immunity Adaptive Immunity
Response time Minutes/hours Days
Specificity Limited & broad Highly specific
Diversity Limited Highly diverse
Memory response No Yes (faster, stronger responses)
Self/non-self discrimination Perfect Very good
Soluble components Antimicrobial peptides/proteins Antibodies
Major cell types Phagocytes (macrophages, neutrophils), NK cells, dendritic cells B cells, T cells

Types of Immune Cells

  • Leukocytes: Neutrophils, macrophages, T cells, B cells (each with specialized functions)

  • Phagocytes: Macrophages (patrol tissues, engulf bacteria), neutrophils (most abundant WBC, engulf bacteria), eosinophils (rare in blood, kill antibody-coated parasites), basophils (rare in blood, inflammatory mediators against parasites), mast cells (in tissues, inflammatory mediators for allergies).

  • Myeloid cells- monocytes (Kidney-bean shaped nucleus, phagocytosis, inflammatory mediators),

  • Agranulocytes- NK cells (kill infected host cells, chemical mediators).

Phagocytosis

  • Internalizing substances through engulfment
  • Steps: Binding, engulfment, killing and degradation

Opsonization

  • Coating a microbe with proteins to aid phagocytosis
  • Example: C-reactive protein (CRP)

NK Cells

  • Kill infected host cells without prior activation
  • Activated by missing MHC class I or by antibody coating of target cell

Cell Killing

  • Antibody-dependent cell-mediated cytotoxicity
  • Infected cells expressing microbial antigens are killed
  • Mechanism: similar to NK cells

Complement

  • Collection of soluble proteins aiding the immune system.
  • Prominent roles: promoting phagocytosis (Opsonisation), increasing inflammation, directly killing pathogens
  • Activation pathways: Classical, alternative, lectin pathways, resulting in lysis of cell membranes.

Cytokines

  • Soluble proteins produced by various cells
  • Roles: Autocrine (acts on producing cell), paracrine (local), endocrine (via blood)
  • Pleiotropy (multiple effects), Redundancy (complementary functions), Synergy (combined effects), Antagonism (opposing actions)
  • Examples: Interleukins (ILs), tumor necrosis factors (TNFs), interferons (IFNs).

Inflammation

  • Localized response (eliminate/wall off injury and dead cells) to promote tissue repair
  • Key symptoms include redness, heat, swelling, pain and functional impairment
  • Steps: PAMP/DAMP detection, mediator release, leukocyte recruitment, trigger elimination, tissue repair
  • Systemic (wide-spread) effects of localized inflammation involve body systems and organs.

Adaptive Immunity

  • Lymphocytes (B and T cells)
  • Antigen recognition
  • Clonal expansion and differentiation (generating effective cells)
  • Antigen elimination
  • Apoptosis: removing excess cells
  • Memory cells: faster responses in subsequent exposures

Antigen Presentation

  • MHC class I: Presents antigens from inside cells to cytotoxic T cells
  • MHC class II: Presents antigens from outside cells to helper T cells

B-cell Activation and Function

  • B-cells recognize antigens directly to activate
  • Produce antibodies to neutralize microbes or toxins
  • Antibody classes (isotypes): IgG, IgE, IgA, IgM, IgD (each with distinct roles)

T-cell Activation and Function

  • Helper T cells (TH): interact with other immune cells to coordinate immune responses, activate B cells, and promote inflammation
  • Cytotoxic T cells (TC): directly kill infected or abnormal cells

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Explore the fundamentals of immunology, including the immune system's roles in defending against infections and tumors, as well as its involvement in tissue repair and inflammatory responses. Understand how the immune system identifies foreign substances and the issues that arise from its dysfunction, such as immunodeficiency and allergies.

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