Immunology Quiz on Immune Responses

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Questions and Answers

What is the primary function of innate immunity?

To eliminate foreign pathogens without previous exposure (correct)

To provide long-term immunity through memory cells

To immediately respond to all pathogens

To recognize and remember specific pathogens

What are the primary lymphoid organs responsible for?

Activating immune responses

Storing immune memory cells

Maturing lymphocytes (correct)

Filtering pathogens from the lymph

Which type of pathogen is considered the most dominant infectious organism in industrialized nations?

Parasites

Fungi

Bacteria

Viruses (correct)

What is the role of cytokines in the immune response?

They communicate between cells of the immune system Signup and view all the answers

What distinguishes adaptive immunity from innate immunity?

Adaptive immunity develops memory for specific pathogens. Signup and view all the answers

Which type of immunity is characterized by an immediate response without requiring prior exposure to a pathogen?

Innate Immunity Signup and view all the answers

Which of the following components are NOT part of the innate immune response?

B Lymphocytes Signup and view all the answers

What role do cytokines play in the immune system?

Facilitate communication between immune cells Signup and view all the answers

Which leukocyte is primarily responsible for combating parasite infections?

Eosinophils Signup and view all the answers

What do dendritic cells and macrophages primarily function as in the immune response?

Antigen-presenting cells Signup and view all the answers

How do natural killer cells differ from other lymphocytes?

They do not require activation. Signup and view all the answers

Which of the following best describes the classical complement pathway?

Requires antibodies for activation Signup and view all the answers

Which physical barrier is primarily responsible for trapping and limiting bacterial adhesion?

Mucous membranes Signup and view all the answers

Which non-cellular component of innate immunity can lyse bacterial cell walls?

Lysozyme Signup and view all the answers

What is the primary function of the complement system?

To kill microbes extracellularly Signup and view all the answers

What is the primary function of antibodies secreted by plasma cells?

To bind pathogens at the infection site or in circulation Signup and view all the answers

Which immunoglobulin class is the first antibody produced after a new infection?

IgM Signup and view all the answers

What role does opsonization play in the immune response?

It tags pathogens for destruction by phagocytes. Signup and view all the answers

Which immunoglobulin class is most abundant in the body and provides long-term memory?

IgG Signup and view all the answers

What is NOT a method by which antibodies lead to pathogen destruction?

Mutation Signup and view all the answers

What is the function of IgE antibodies?

They are involved in allergic reactions and parasite infections. Signup and view all the answers

How do vaccinations induce immunity?

By providing noninfectious antigens to generate a mild immune response. Signup and view all the answers

What is a key characteristic of the structure of antibodies?

Made up of interlinked two heavy chains and two light chains. Signup and view all the answers

What is the primary role of T cells in the immune response?

To coordinate the immune response Signup and view all the answers

Which type of MHC molecules do cytotoxic T cells bind to?

Class I MHC Signup and view all the answers

How do B cell receptors function in relation to antigens?

They bind to antigens like a lock and key. Signup and view all the answers

What is the function of Helper T cells (Th cells)?

To stimulate B cells and cytotoxic T cells Signup and view all the answers

What triggers the inflammatory response upon pathogen invasion?

Entry of pathogens into tissues causing tissue injury Signup and view all the answers

What is the main function of plasma cells in the immune response?

To produce and secrete antibodies Signup and view all the answers

What happens when a cytotoxic T cell is activated?

It undergoes proliferation and differentiation. Signup and view all the answers

What role do antigen-presenting cells (APCs) play in the adaptive immune response?

They present antigens to T cells for activation. Signup and view all the answers

What is the role of chemotaxis in the inflammatory response?

To attract immune cells to the site of infection Signup and view all the answers

Which statement about human leukocyte antigen (HLA) complexes is correct?

They aid in tissue transplantation matching. Signup and view all the answers

How does the adaptive immune response differ from the nonspecific immune response?

Adaptive response is highly specific to pathogens. Signup and view all the answers

What initiates the vasodilation process during the inflammatory response?

Release of signaling chemicals from injured tissues Signup and view all the answers

Which of the following is NOT a component of adaptive immunity?

Natural killer cells Signup and view all the answers

Study Notes

Immunology

The study of how the body ("host") recognizes self from nonself ("pathogens")
Goal: Eliminate foreign matter without damaging the host

Types of Pathogens

Viruses
Bacteria
Fungi
Parasites

Lymphoid Organs

Primary Lymphoid Organs - Responsible for the maturation of lymphocytes
- Bone marrow: Site of B cell maturation
- Thymus: Site of T cell maturation
Secondary Lymphoid Organs - Activation of lymphocytes during a specific immune response
- Lymph nodes (LN)
- Spleen
- Tonsils/adenoids
- Lymphocyte accumulations in the gut, respiratory, genital, and urinary tracts (e.g., GALT, BALT)

The Immune System

Two main parts:
- Innate Immune Response
- Adaptive Immune Response

Innate Immunity

Present at birth
Acts immediately
Does not require activation
Nonspecific
Recognizes carbohydrates and lipids on foreign cells
Leukocytes circulate in the blood

Adaptive Immunity

Acquired through exposure to pathogens
Takes time to develop
Requires activation
Specific - forms memory cells
Recognizes proteins on foreign cells
Lymphocytes present in secondary lymphoid organs

Components of Innate Immunity

Physical Barriers:
- Skin
- Epithelium
- Mucous membranes
Chemical Barriers:
- Lysozyme
- Sweat
- Stomach acid
Cellular Components (Leukocytes):
- Polymorphonuclear Granulocytes (PMNs):
  - Neutrophils: Most numerous, secrete bleach and peroxide, avid phagocytes, elevated in bacterial infections.
  - Basophils: Secrete histamine, related to mast cells (in skin and mucus membranes).
  - Eosinophils: Fight parasite infections, elevated in allergies.
- Macrophages: Derived from monocytes, found where epithelium meets external environment (skin, gastrointestinal and respiratory tract), engulf particles by phagocytosis, act as Antigen-presenting cells (APCs).
- Dendritic cells: Macrophage-like cells, act as APCs.
Non-cellular Components:
- Complement: A group of plasma proteins that kill microbes extracellularly, synthesized in the liver and circulate in the blood.
- Cytokines: Protein messengers released by cells of the immune system.
Inflammation: Local response to infection or injury

Physical and Chemical Barriers

Skin: Few microorganisms can penetrate intact skin.
Epithelium (Gastrointestinal and Respiratory System):
- Mucous membranes: Sticky, traps and limits bacterial adhesion to epithelium.
- Hair and cilia: Trap and sweep away particulate matter.
Lysozyme: Enzyme that lyses bacterial cell walls, found in tears, saliva, milk, and mucus.

Cellular Components

Leukocytes:
- Neutrophils: Most numerous, secrete bleach and peroxide, avid phagocytes, elevated in bacterial infections.
- Basophils: Secrete histamine, related to mast cells (in skin and mucus membranes).
- Eosinophils: Fight parasite infections, elevated in allergies.
- Macrophages: Derived from monocytes, found where epithelium meets external environment (skin, gastrointestinal and respiratory tract), engulf particles by phagocytosis, act as Antigen-presenting cells (APCs).

Non-Cellular Components

Complement: Family of plasma proteins (30+ proteins)
- Triggers extracellular killing of microbes
- Synthesized in the liver and circulates in the blood
- Activated by infection or damage
- Forms the membrane attack complex (MAC) that causes cell lysis
Cytokines: Protein messengers released by cells of the immune system
- Facilitate communication within the immune system
- Often act in cascades, with one cytokine stimulating the release of another
- Play a role in both innate and adaptive immune responses
- Types: Interleukins (IL-1, IL-2, etc.), Interferons (IFN), Chemokines, Lymphokines, Tumor Necrosis Factor (TNF)

Inflammatory Response

Nonspecific immune response to invasion by pathogen (similar response to trauma, cold, heat injury)
Steps:
1. Entry of bacteria into tissue, causing tissue injury and chemical release.
2. Vasodilation (increased blood flow) in the infected area (warmth, redness, swelling).
3. Increased permeability of capillaries and venules.
4. Chemotaxis: Movement of leukocytes into interstitial fluid and tissue.
5. Destruction of bacteria by phagocytosis or other mechanisms.

Adaptive Immune Response

Two types:
- Cell-mediated Immunity: Carried out by activated T cells.
- Humoral-mediated Immunity: Carried out by activated B cells.

Components of Adaptive Immunity

Cellular Components:
- B lymphocytes (B cells): CD19, CD20, responsible for humoral-mediated immunity.
- T lymphocytes (T cells): Responsible for cell-mediated immunity.
  - Cytotoxic T cells (Tc, CD8): Kill infected cells directly.
  - Helper T cells (Th, CD4): Coordinate immune response.
Antigen-presenting cells (APCs): Required for the activation of adaptive immune cells.

B Cell Receptors

Antibodies on the surface of B cells
Bind to specific antigens like a lock and key

T Cell Receptors

Do not directly recognize antigens
Recognize antigens presented on major histocompatibility complexes (MHCs)
MHCs are unique to each person and act as genetic "identity tags" of self.
Two classes of MHCs:
- Class I MHC: Found on all nucleated cells (except red blood cells).
- Class II MHC: Found only on the surface of macrophages, dendritic cells, and B cells.
T cell receptors can only recognize an antigen if it is bound to an MHC.
- Cytotoxic T Cells (CD8): Bind to Class I MHC.
- Helper T Cells (CD4): Bind to Class II MHC.

Human Leukocyte Antigen (HLA) Complexes

Human version of the major histocompatibility complex
Encoded by a cluster of genes on chromosome 6
Used to match for tissue transplantation to prevent rejection
Certain HLA types are associated with specific autoimmune diseases
Some HLA-mediated diseases may predispose to cancer

Details of Adaptive Immunity

Helper T Cells (Th): Coordinate the immune response to a specific pathogen, do not directly attack, but begin and coordinate the response.
- Enhance inflammation
- Stimulate cytotoxic T cells
- Stimulate B Cells
- Activated by antigen-presenting cells, producing IL-2.
- Two types: Th1 (cell-mediated) and Th2 (humoral), typically in balance.
- IL-2 causes helper T cells to proliferate and differentiate into:
  - Memory helper T cells (remember the specific antigen)
  - Effector helper T cells (coordinate immune response)
Cytotoxic T Cells (Tc): Kill infected cells directly.
- Activated by antigen-presenting cells.
- IL-2 from helper T cells causes Tc proliferation and differentiation into:
  - Memory cytotoxic T cells (remember the specific antigen)
  - Effector cytotoxic T cells (migrate to the site of infection and kill pathogens or infected cells).
B cells:
- Sensitized to antigen either by phagocytosis or antigen-presenting cells.
- Receive signals from helper T cells via IL-4, causing proliferation and differentiation into:
  - Memory B cells (remember the specific antigen)
  - Plasma cells (remain in secondary lymphoid organs and secrete antibodies).

How Do Antibodies Destroy Pathogens?

Antibodies are secreted by plasma cells into lymph and blood.
Bind to pathogens at the site of infection or in circulation.
Destroy pathogens in three ways:
- Neutralization: Prevents virus or bacteria from binding to host cells.
- Opsonization: Tags a pathogen for destruction by phagocytes.
- Complement activation: Destroys pathogen by forming pores in the cell membrane.

Immunoglobulins

Family of proteins that includes B cell receptors and plasma cell antibodies.
Composed of four interlinked chains:
- Two heavy chains (long chains): Stem is distinct for each Ig type.
- Two light chains (short chains): Contain constant and variable regions.

Immunoglobulin Classes

"MADGE"
- IgM: First antibody produced after new infection, transient.
- IgG: Most abundant, crosses placenta, long-term memory, active in secondary response.
- IgE: Involved in allergic reactions and parasite infections (found on mast cells and basophils).
- IgA: Mucosal immunity, found where the body interacts with the external environment (gastrointestinal, respiratory, genitourinary systems), secreted in breast milk.
- IgD: Found in blood and lymph, function unknown.

Vaccination to Induce Immunity

Contains noninfectious antigens from known pathogens to generate a mild primary immune response.
Leads to immune memory (memory B cells, IgG).
When exposed to the pathogen, the immune system mounts a quick and robust response.

Immunologic Testing

Polymerase Chain Reaction (PCR): Detects genetic material from an organism or pathogen.

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Description

Test your knowledge on the fundamentals of immunology, including the recognition of pathogens and the functions of lymphoid organs. Explore the differences between innate and adaptive immune responses. This quiz covers key concepts essential for understanding the immune system.