Immune Defenses and Lymphatic System Quiz

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Questions and Answers

What role do mucosal surfaces play in immune defense?

They help in the maturation of T cells.

They serve as a barrier against external infections. (correct)

They produce red blood cells for oxygen transport.

They promote the growth of pathogens.

What initiates the inflammatory response in the body?

The activation of pattern recognition receptors. (correct)

The presence of red blood cells.

The formation of new lymphatic vessels.

The gradual deterioration of external epithelia.

Which of the following best describes the function of lymph nodes?

They transport oxygen throughout the body.

They transport carbon dioxide out of the bloodstream.

They filter and store nutrients for immune responses.

They serve as hubs for immune cell interaction and activation. (correct)

What is the primary function of the thymus in the immune system?

To develop and mature T cells. Signup and view all the answers

Which of the following is NOT a classic sign of inflammation?

Dizziness Signup and view all the answers

What is the main function of neutrophils in the innate immune response?

Engulf and kill pathogens Signup and view all the answers

Which type of immune response is characterized by limited specificity and quick action following an infection?

Innate immunity Signup and view all the answers

What distinguishes dendritic cells from other phagocytic cells in the immune system?

Migration to lymph nodes to present antigens Signup and view all the answers

What role does the complement system play in the immune response?

Directly kills pathogens or attracts immune cells Signup and view all the answers

How do innate and adaptive immune responses differ in terms of memory?

Only adaptive responses exhibit long-lived immune memory Signup and view all the answers

What is the primary role of macrophages in the immune system?

Engulf and kill pathogens Signup and view all the answers

What triggers the adaptive immune response?

The innate immune response Signup and view all the answers

Which characteristic is NOT associated with adaptive immune responses?

Limited memory Signup and view all the answers

Which class of antibodies is the most abundant in serum?

IgG Signup and view all the answers

Which type of T cell recognizes antigens presented on MHC class I molecules?

CD8 T cells Signup and view all the answers

What distinguishes B cell receptors from T cell receptors?

BCRs can bind to native proteins directly. Signup and view all the answers

Which of the following roles do CD4 T cells perform?

Enhance other immune cell responses. Signup and view all the answers

What is the primary location for the activation of adaptive immune cells?

Lymph nodes Signup and view all the answers

What is a key feature of immunological memory in the adaptive immune system?

It allows rapid response upon reinfection. Signup and view all the answers

What distinguishes IgE antibodies from other classes?

They are primarily involved in allergic responses. Signup and view all the answers

Which of the following statements about T cell differentiation is true?

T cells decide how to respond during activation. Signup and view all the answers

Which statement accurately describes the difference between innate and adaptive immune responses?

Adaptive responses provide long-term immunity. Signup and view all the answers

The spike protein is an example of what?

An antigen on the surface of certain viruses. Signup and view all the answers

Study Notes

Immune Defences

External Epithelia: Skin, mucous membranes (airways, gastrointestinal tract, reproductive tract) provide the first line of defense.
Secretions: Mucus, cilia, defensins act as additional barriers.
Inflammation: Occurs when barriers are breached; involves activation of pattern recognition receptors, triggering release of signaling molecules like histamine, peptides, cytokines, and chemokines.
Signs of Inflammation: Pain, heat, redness, swelling.

Lymphatic System

Lymphatic Vessels: Transport lymph throughout the body.
Lymph Nodes: Intersections of lymphatic vessels, acting as immune cell hubs for interaction and activation.
Lymph: Colorless fluid containing white blood cells that circulates within the lymphatic system.
Thymus: Organ responsible for T cell development and maturation.
Spleen: Filters blood, removes damaged red blood cells, and stores white blood cells.

Immune Cells

Blood: Contains red blood cells (oxygen transport) and white blood cells (immune defense).

Red Blood Cells

Carry oxygen.
5-6 million per microliter of blood.
Production rate: ~2 million per second.
Lifespan: ~110 days.
Transport oxygen and carbon dioxide.

White Blood Cells

Immune cells, numerous types including: neutrophils, macrophages, monocytes, eosinophils, mast cells, basophils, T cells, B cells, and dendritic cells.
Classified as innate or adaptive immunity.

Innate Immunity

Initial response (within 12 hours) to danger signals and activation of immune cells.
Limited specificity.
Found in all tissues, especially at barrier sites.
Rapid response following infection.
Limited memory.

Adaptive Immunity

Takes longer to activate (days following barrier breach).
Highly specific to particular proteins/antigens.
Primarily found in lymphoid organs.
Long-lasting memory.

Key Players In Innate Immunity:

Neutrophils: Most abundant white blood cell, active phagocytic cells, engulf and kill pathogens, employ neutrophil extracellular traps (NETs) to trap and kill pathogens, short-lived.
Macrophages: Develop from precursors in tissues, active phagocytic cells, consume and kill pathogens, activated by inflammation, long-lived.
Dendritic Cells: Develop from precursors in tissues, active phagocytic cells, migrate from peripheral tissues to lymph nodes, transport antigens to T cells in lymph nodes, bridge innate and adaptive immunity by activating the adaptive immune response.
Complement: Cascade of proteins in serum (blood) that sense danger, enhances immune response, activated by antibodies or pathogen molecules, can directly kill pathogens or attract immune cells to an infection site.

Stages of Adaptive Immune Response:

Triggered by innate immune response.
Dendritic cells, macrophages, and neutrophils signal to adaptive immune cells.
Innate immune cells can clear mild infections; otherwise, they alert adaptive immune cells.

T Cell Activation: Finding the right T and B cells.
T Cell Differentiation: Deciding how to respond.
T Cell Effector Stage: Immune response.

B Cells

B cell receptors (BCRs) can bind to native proteins or antigens without accessory cells (processing not required).
Up to 10^12 different BCRs.
Produce antibodies, classified into different types:
- IgM: Low affinity, high avidity.
- IgG: Most abundant antibody in serum.
- IgA: Found at mucosal sites.
- IgE: Involved in allergy and anti-helminth worm responses.
Antibodies are made by plasma cells (differentiated B cells).
Antibody mechanisms:
- Neutralize pathogens.
- Activate complement to enhance immune response.
- Enhance phagocytosis (opsonization) by binding to receptors on phagocytes.

T Cells

Around 10^8 different T cell receptors (TCRs).
T cells recognize processed antigens presented on MHC molecules on the surface of antigen-presenting cells (require accessory cells).
CD4 T cells (Helper T cells):
- Recognize longer peptides on MHC class II molecules, expressed by professional antigen-presenting cells (B cells, macrophages, dendritic cells).
- Support other immune cells by:
  - Enhancing CD8 T cell responses.
  - Aiding B cells in producing high-affinity antibodies.
  - Activating macrophages for more effective pathogen destruction.
CD8 T cells (Cytotoxic T cells):
- Recognize shorter peptides on MHC class I molecules, expressed by all nucleated cells (B cells, macrophages, dendritic cells, epithelial cells).
- Kill infected cells and tumor cells by releasing toxic granules.
Memory trick: 4 x 2 = 8 (CD4 T cells with MHC class II), 8 x 1 = 8 (CD8 T cells with MHC class I).

Specificity:

Spike Protein: Antigen found on the surface of some viruses.
Epitope: Peptide chains, parts of an antigen recognized by immune receptors (BCRs and TCRs).

Adaptive Immune Cell Locations:

Generation: Primary lymphoid organs (thymus and bone marrow).
Activation: Secondary lymphoid organs (lymph nodes and spleen).

Timings of the Immune Response:

Innate: 0-5 days (dendritic cells, neutrophils, macrophages, monocytes).
Adaptive: 3-15 days (B cells, CD4 T cells, CD8 T cells).
Long-lived: Months to years (long-lived plasma cells, memory B and T cells).

Immunological Memory

Enables rapid control of previously encountered pathogens.
Memory T and B cells provide a rapid response upon reinfection.
Memory cells act at different locations in the body to protect the host.

Key Points

B and T cells form the adaptive immune system.
Specialized receptors (BCRs and TCRs) on their surfaces allow recognition of antigens.
B cells produce pathogen-specific antibodies.
CD4 T cells coordinate other immune cells.
CD8 T cells kill infected cells and tumors.
Memory T and B cells ensure rapid responses to previously encountered pathogens.

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Description

Test your knowledge on the body's immune defenses, including the role of external epithelia, secretions, and inflammation. Explore the functions of the lymphatic system, including lymph transport and immune cell interaction within lymph nodes. This quiz covers essential concepts about immune cells and their functions.