Overview of Physiological Systems and Immune System

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Questions and Answers

Which of the following correctly describes the role of MHC molecules in T cell recognition?

MHC molecules present antigens to B cells, triggering the production of antibodies.

MHC molecules present small peptide fragments of antigens to T cells, allowing for specific recognition. (correct)

MHC molecules act as receptors on T cells, recognizing and binding to specific antigens.

MHC molecules directly bind to antigens, initiating an immune response.

How does the clonal selection theory account for the immune system's ability to mount specific responses to a vast array of pathogens?

Each immune cell is pre-programmed to recognize a specific pathogen and produces antibodies against it.

Immune cells adapt their receptors to match the specific pathogen encountered, allowing for a targeted response.

Immune cells differentiate into specialized types based on the specific pathogen they encounter.

The immune system randomly generates a diverse repertoire of receptors, and only those cells with receptors that specifically recognize the pathogen are activated and proliferate. (correct)

Which of the following is NOT a characteristic of T cell receptors (TCRs)?

TCRs are expressed on the surface of T cells.

TCRs bind to antigens directly without the need for MHC presentation. (correct)

TCRs are highly diverse, allowing for recognition of a vast array of antigens.

TCRs are encoded by rearranged genes.

What is the significance of the discovery by Hozumi and Tonegawa regarding BCR gene rearrangement?

It explained how antibodies can be so diverse, enabling the immune system to recognize a wide range of antigens. (B) Signup and view all the answers

What is the primary function of CD8+ T cells?

To directly kill infected cells or cancer cells. (A) Signup and view all the answers

How does the immune system prevent autoimmune reactions, where it attacks its own tissues?

Cells that react strongly to self-antigens are eliminated during early development, preventing the activation of autoreactive immune cells. (A) Signup and view all the answers

What is the significance of the discovery that matching immune systems improves transplant survival?

It demonstrated the role of MHC molecules in organ transplant rejection. (C) Signup and view all the answers

Which of the following scientists is credited with developing the Clonal Selection Theory?

Macfarlane Burnet (A) Signup and view all the answers

Which type of MHC molecule presents antigens to CD4+ T cells?

MHC class II (C) Signup and view all the answers

What distinct function do dendritic cells perform in the immune response?

Capture pathogens and present their pieces to other immune cells (A) Signup and view all the answers

Which of the following statements correctly describes the role of neutrophils in the immune system?

They release DNA nets (NETs) to trap pathogens (C) Signup and view all the answers

Which component of the phagolysosome is primarily responsible for breaking down bacterial walls?

Lysozyme (A) Signup and view all the answers

Which type of white blood cell is primarily responsible for carrying oxygen in the blood?

Red Blood Cells (RBCs) (C) Signup and view all the answers

What property of the phagolysosome helps kill most germs?

Low pH (acidic environment) (D) Signup and view all the answers

Which function of cytokines is primarily responsible for drawing immune cells to sites of infection?

Chemokines (C) Signup and view all the answers

What is the primary role of neutrophils in the immune response?

Act as first responders to infections (B) Signup and view all the answers

Which of the following best describes the process of phagocytosis as outlined in the immune response?

Engulfment of pathogens into a phagosome (A) Signup and view all the answers

Which family of cytokines is primarily associated with inducing inflammation and cell death?

Tumor Necrosis Factor Family (C) Signup and view all the answers

How does the JAK-STAT pathway primarily function upon receiving a cytokine signal?

Activates proteins that move into the nucleus to influence gene activation (A) Signup and view all the answers

What is the function of DAMPs in the immune system?

Alert the immune system of cellular damage (C) Signup and view all the answers

Which toxic molecule is NOT typically produced during the destruction of pathogens in phagocytosis?

Lactoferrin (B) Signup and view all the answers

What function do the effectors serve in the immune response?

They eliminate threats like bacteria. (A) Signup and view all the answers

What is the role of the non-effectors in the immune response?

To modify their functions supporting immunity. (C) Signup and view all the answers

Which of the following triggers inflammation through internal mechanisms?

Heat shock proteins released during injury. (D) Signup and view all the answers

Which molecule is primarily responsible for promoting inflammation and can kill cells?

TNFα (Tumor Necrosis Factor-alpha) (B) Signup and view all the answers

What does a negative feedback loop achieve in the context of inflammation?

Ceasing inflammation to prevent tissue damage. (C) Signup and view all the answers

What external trigger interacts with cellular receptors to initiate an inflammatory response?

Toxins from venom or phytochemicals. (A) Signup and view all the answers

What is primarily raised during inflammation to slow down bacterial growth?

Body temperature. (A) Signup and view all the answers

Who was instrumental in developing the first rabies vaccine and what was his approach?

Louis Pasteur; utilizing an attenuated form of the rabies virus. (B) Signup and view all the answers

What is the function of feedforward loops in response to inflammation?

To help the body adapt to ongoing inflammation. (D) Signup and view all the answers

Study Notes

Overview of Physiological Systems and the Immune System

Physiological systems are circular, without a clear beginning or end, maintaining a balance called homeostasis
The immune system is complex and interconnected, requiring a breakdown of its parts to understand its function
Understanding the immune system is crucial to understanding its responses and functions

Key Questions About the Immune System

How do we know we have an immune system?
- When injured, the area swells, turns red, and heals
- Allergies demonstrate the system's ability to react to substances
- The immune system learns from infections and avoids repeating the same illness
How do we know we need an immune system?
- Some children are born with no immune system, and without treatment, they cannot survive infections.
- Experiments with animals show the immune system is necessary for survival.

What is the purpose of the immune system?

Defends against invaders (bacteria, viruses)
Distinguishes self from non-self to avoid attacking the body's own tissues
Detects and targets threats to the body
Maintains harmony with harmless microorganisms that live in the body (good bacteria)

Components of the Immune System

Barriers (today's focus)
Cells (e.g., white blood cells)
Molecules (e.g., antibodies)

Barriers: The First Line of Defense

Mechanical Defenses: physical actions or structures that prevent harmful things from entering the body
- Epithelial cells joined by tight junctions: prevent invaders like bacteria or viruses from entering.
- Longitudinal flow of fluids (saliva, urine, etc.): washes away harmful substances
- Movement of mucus by cilia: removes dirt and germs from the respiratory system
- Tears and nasal cilia: removes harmful particles
Chemical Defenses: substances the body produces to kill or stop harmful invaders
- Fatty acids: create an environment where bacteria struggle to survive
- Low pH (acidic environment): kills most bacteria in food
- Enzymes (pepsin): breaks down harmful substances or kills bacteria
- Pulmonary surfactant: helps keep harmful germs away
- Molecules that directly attack invaders (ß-defensins, a-defensins, RegIII, cathelicidins, and histatins): kill bacteria, fungi, or other harmful organisms
Microbiological Defenses: normal microbiota living on the skin and inside the body
- Takes up space and nutrients, preventing harmful bacteria from growing
Nutritional Barriers: body tightly controls important nutrients, like iron, to prevent bacteria from thriving

Innate Immunity

Present at birth and inherited from parents
Fast but non-specific (reacts the same way to all threats)
Encoded by genes that don't change much over generations (found in all living organisms)
No "true memory"

Adaptive Immunity

Develops over time as we encounter antigens.
Slower initially but highly specific and improves with repeated exposure.
Encoded by genes that recombine to create unique immune responses.
Found mainly in advanced animals (humans)
Remembers past infections and responds faster and stronger next time (immunological memory)

Cells of the Immune System

Adaptive Immunity Cells
- T cells: attack infected cells directly
- B cells: produce antibodies to fight specific germs
- Natural Killer (NK) cells: kill harmful cells without needing prior instructions
Innate Immunity Cells
- Neutrophils: first responders to infection or injury, eat germs (phagocytosis)
- Macrophages: eat germs and clean up dead cells
- Dendritic Cells: act as messengers between innate and adaptive immunity, capture germs
- Mast Cells: found in tissues; release chemicals to help fight infections

How the Immune System Recognizes Pathogens

Immune cells have sensors (Pattern Recognition Receptors (PRRs)) to detect germs
These receptors are located on cell surfaces, inside the cell (cytoplasm), or inside cellular compartments (endosomes)
There are different families of PRR families including TLRs, CLRs, NLRs, and RLRs
Pathogen-Associated Molecular Patterns (PAMPs) are unique features that PRRs recognize

Phagocytosis

Immune cells engulf and destroy germs forming a phagolysosome (phagosome + lysosome).
The phagolysosome uses low pH, toxic molecules (hydrogen peroxide, bleach-like chemicals), and enzymes.

Blood Composition

Plasma: liquid part of blood, containing hormones, antibodies, and nutrients.
Cells (45%): red blood cells (carry oxygen), white blood cells (fight infections), platelets (help blood clot).

Blood Cell Formation

Blood cells are made in the bone marrow from stem cells
Stem cells produce myeloid cells (neutrophils, macrophages, dendritic cells) and lymphoid cells (T cells, B cells, NK cells).

Founders of Immunology

Paul Ehrlich: discovered antibodies
Elie Metchnikoff: discovered phagocytosis

Overview: Anatomy of the Immune Response

Three main stages
- Barrier Immunity: Physical barriers prevent germs from entering (skin, mucus, etc.)
- Innate Immunity: First line of defense (immediate but general)
- Adaptive Immunity: Second line of defense – slower but highly specific

Immune System Organization

Circulates throughout the body
Made of cells and molecules working together

Primary Organs

Bone Marrow: produces immune cells
Thymus: matures T cells
Secondary Organs
- Lymph Nodes: hubs for immune cells
- Spleen: recycles old red blood cells, houses immune cells to fight infections

The Lymphatic System

Network of vessels and nodes parallel to the circulatory system
Transports immune cells and germs to lymph nodes
Returns immune cells to infection sites
Contains different compartments:
- Cortex (B-cell production)
- Paracortex (T-cell function/production)
- Medulla (macrophage and plasma cells complete the immune response)

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Description

This quiz covers the essential aspects of physiological systems, focusing particularly on the immune system. It explores how these systems maintain homeostasis and the critical functions of the immune response. Understanding these concepts is key to grasping how our body protects itself against infections.