Human Immune System

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Questions and Answers

What type of immunity is characterized by immune cells attacking anything viewed as foreign to the host?

Nonspecific defense

Adaptive immunity

Specific immunity

Innate immunity (correct)

What is the primary function of the first two lines of defense in innate immunity?

To produce antibodies against specific antigens

To recognize and target specific microorganisms

To prevent pathogens from entering the body in the first place (correct)

To eliminate pathogens that have already entered the body

Which layer of the skin is composed of many layers of tightly packed cells that prevent pathogens from penetrating?

Basal layer

Epidermis (correct)

Stratum corneum

Dermis

What happens to the dead and dying cells in the epidermis?

They are continually sloughed off along with any pathogens Signup and view all the answers

What is the main difference between innate and adaptive immunity?

Innate immunity is present from birth, while adaptive immunity is acquired Signup and view all the answers

What is the function of the dermis in relation to the immune system?

It contains hair follicles, glands, and nerve endings Signup and view all the answers

What is the purpose of the continual division and pushing of cells to the surface of the epidermis?

To remove microbes from the skin's surface Signup and view all the answers

Which type of immunity involves the recognition and targeting of specific microorganisms?

Adaptive immunity Signup and view all the answers

What type of cells in the respiratory tract secrete mucous to trap microbes?

Goblet cells Signup and view all the answers

Which of the following is NOT a function of the GU/Reproductive tract in preventing microbial infection?

Production of lysozymes in the urethra Signup and view all the answers

What is the main function of cilia in the respiratory tract?

To propel microbe-containing mucus out of the respiratory tract Signup and view all the answers

Which of the following tracts has a high acidity that helps to kill most microbes?

GI tract Signup and view all the answers

What is the term for the normal microbial life that exists on and within a body at any given time?

Microbial flora Signup and view all the answers

Which of the following is a function of saliva in the mouth?

To contain lysozymes and other antimicrobial molecules Signup and view all the answers

What is the primary function of collagen in the dermis?

To provide strength and elasticity to the skin Signup and view all the answers

Which of the following is NOT a type of chemical barrier protection in the skin?

Keratinocytes Signup and view all the answers

What is the primary function of defensins in the skin?

To produce antimicrobial peptides Signup and view all the answers

What is the primary function of lysozymes in the skin?

To break down bacterial cell walls Signup and view all the answers

What is the function of sebum in terms of antimicrobial function?

To keep the skin pliable and lower the skin pH Signup and view all the answers

What is the primary function of mucous membranes in the body?

To cover all body cavities that are open to the environment Signup and view all the answers

What is the primary function of phagocytosis?

To consume and digest pathogens Signup and view all the answers

Which type of interferon is secreted by fibroblasts?

INF-β Signup and view all the answers

What is the term for the process of a pathogen being covered by antibodies or complement proteins to make it easier for phagocytic cells to recognize?

Opsonization Signup and view all the answers

What is the function of eosinophils in parasitic infections?

To attach to the surface of parasitic helminths and secrete toxins Signup and view all the answers

What is the primary function of natural killer cells?

To release toxic proteins to destroy virally infected cells Signup and view all the answers

What is the term for the site where leukocytes are produced?

Red bone marrow Signup and view all the answers

What is the primary function of the complement system?

To induce killing via opsonization or cell lysis Signup and view all the answers

Which genetic mutation provides HIV immunity?

Mutation in the CCR5 receptor Signup and view all the answers

What is the term for the engulfed pathogen-coated membrane vesicle?

Phagosome Signup and view all the answers

What is the term for the process by which certain microbial components, chemicals released from damaged tissues, and chemokines attract neutrophils and macrophages?

Chemotaxis Signup and view all the answers

What is the primary mechanism by which the activation of complement occurs?

In a cascade, where each component initiates the next step in the pathway Signup and view all the answers

Which type of immunity is characterized by the activation of the classic pathway?

Adaptive immunity Signup and view all the answers

What is the primary function of the membrane attack complex (MAC) formed in the alternate pathway?

To create a hole in the cell wall of bacteria, causing lysis Signup and view all the answers

What is the primary purpose of inflammation?

To eliminate the pathogen and repair tissue Signup and view all the answers

What is the primary cause of pain in inflammation?

All of the above Signup and view all the answers

What is the result of increased vascular permeability in inflammation?

Fluid leakage from vessels into tissues, causing edema Signup and view all the answers

What is the primary purpose of phagocytic mobilization in inflammation?

To destroy invading pathogens Signup and view all the answers

What is the characteristic of the Gram (-) bacterial cells that makes them more susceptible to the effects of the membrane attack complex (MAC)?

Thinner cell walls Signup and view all the answers

Study Notes

Immune System

The immune system is composed of two divisions: Innate Immunity and Adaptive Immunity.
Innate Immunity is also known as nonspecific immunity, where immune cells attack anything they view as foreign to the host.
Adaptive Immunity, also known as specific immunity, involves immune cells targeting specific microorganisms.

Innate Immunity

Innate Immunity is composed of three main lines of defense:
- The first two lines are part of Innate Immunity (nonspecific immunity).
- The third line of defense involves methods of immunity for specific pathogens following exposure and is part of Adaptive Immunity (specific immunity).

First Line of Defense

The body's natural barriers and secretions:
- Prevent pathogens from entering the body in the first place.
Mechanical and Chemical Barriers:
- Skin:
  - The largest organ of the body, composed of two main layers: Epidermis and Dermis.
  - Provides physical barrier protection:
    - Epidermis made up of many layers of cells that are tightly packed together, preventing pathogens from penetrating unless injured.
    - Dermis contains tough fibers called collagen, giving strength and elasticity to skin, allowing it to withstand damage and puncture.
- Chemical Barrier Protection:
  - Dendritic cells in the epidermis perform phagocytosis against colonization and infection by pathogens.
  - Defensins, antimicrobial peptides, are produced by sweat glands to kill microbes on the skin.
  - Lysozymes destroy cell walls of bacteria by breaking bonds between sugar molecules.
  - Sebum, an oily substance secreted by sebaceous glands in the dermis, has two methods of antimicrobial function:
    - Keeps skin pliable, making it more resistant to injury.
    - Lowers skin pH to around 5, inhibiting bacterial growth.
Mucous Membranes:
- Mucous secreting membranes cover all body cavities open to the environment.
- Examples:
  - Respiratory tract: Goblet cells secrete mucous that traps microbes, and ciliated cells propel microbe-containing mucus out of the respiratory tract.
  - GI tract: High acidity (low pH) of the stomach kills most microbes, and saliva contains lysozymes and other antimicrobial molecules.
  - GU/Reproductive tract: Mucous membrane provides a physical barrier to infection, and urine flushes microbes out of the urethra.
  - Eyes: Lacrimal glands produce lysozymes in tears.

Normal Microbial Flora

Microbial flora refers to the normal microbial life that exists on and within a body at any given time.
Most microbial life is harmless and beneficial to humans.
Examples:
- E. coli in the human gut produces Vitamin K as a byproduct of its metabolic reactions, which human cells can then utilize.
- Normal microbial life consumes available nutrients and makes life inhospitable to other microbes.
- It also changes pH, creating an environment hospitable to existing microbial life.

Innate Genetic Immunity

Some individuals are born with genes that offer them protection from certain pathogens.
Examples:
- HIV Immunity: About 1% of the population has a mutation in the CCR5 receptor, preventing HIV from entering T cells.
- Malaria Immunity: Patients with Sickle Cell Disease are immune from malarial infection due to the shape of their red blood cells.

Second Line of Defense

This occurs when the first line of defense is breached and is carried out by different cells and chemical mediators.
Leukocytes (White Blood Cells):
- Granulocytes:
  - Basophils: Release histamine in inflammatory response.
  - Eosinophils: Target parasites and play a role in asthma and some allergic reactions.
  - Neutrophils: Perform phagocytosis.
- Agranulocyte:
  - Lymphocyte:
    - B cell: Involved in adaptive immunity.
    - T cell: Involved in adaptive immunity.
    - NK (natural killer) cell: Targets virally infected cells and cancer cells.
  - Monocyte:
    - Macrophage: Performs phagocytosis.

Phagocytosis

The consumption of a pathogen.
Primarily performed by neutrophils and macrophages.
Occurs in five steps:
- Chemotaxis: Attraction of neutrophils and macrophages to the pathogen.
- Adherence: Attachment of macrophages and neutrophils to the pathogen.
- Ingestion: Formation of a phagosome by coating the pathogen in a membrane.
- Death of Pathogen: Fusion of the phagosome with a lysosome containing hydrolytic enzymes and digestive chemicals.
- Elimination: Removal of remnants of the pathogen via exocytosis.

Opsonization

Process by which a pathogen is covered by antibodies or complement proteins to make it easier to be recognized by phagocytic cells.

Eosinophils

Attach to surface of parasitic helminths (worms) and secrete toxins that weaken/kill the parasite.

NK Cells

Create toxic proteins, called porforins, which destroy the cell membrane of virally infected cells, certain tumor cells, and some varieties of parasites.

Interferon (INF)

Protein molecules released by host cells in the presence of several pathogens, particularly viruses.
Virally infected cells produce a small protein that spreads to neighboring cells and induces them to produce antiviral proteins that prevent viral replication from occurring.

Complement System

A system of about 30 proteins, produced by the liver, which circulate through the bloodstream in an inactivated state.
Can induce killing via opsinization (leads to phagocytosis) or cell lysis.

Inflammation

Inflammation serves to localize the effects of injury (infection, toxin), minimize these effects, and destroy the pathogen when possible. It also sets the stage for tissue repair.
Cardinal signs of inflammation: Rubror (redness), Calor (heat), Tumor (swelling), Dolor (pain), and Functio laesa (impaired function).
Stages of Inflammation:
- Injury releases chemical mediators, causing vasodilation, increased blood flow, and increased vascular permeability.
- Increased permeability leads to fluid leaking from vessels into tissues, causing edema.
- Pain may be caused by release of chemical mediators, nerve irritation by toxins, or pressure on nerves from edema fluid.
- Vasodilation and hyperemia deliver clotting factors to the site of injury, or phagocytic cells to destroy invading pathogens.

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Description

Learn about the two divisions of the immune system: innate immunity and adaptive immunity, and how they protect the body against pathogens.