Microbiology Chapter 12

What are the three lines of host defenses?

The first line is barriers that block invasion, the second line is protective cells and fluids, and the third line is specific immune responses by lymphocytes.

What is the role of the first line of defense?

It blocks invasion at the portal of entry and limits access to internal tissues.

Why is the first line of defense not considered a true immune response?

Because it does not involve recognition of foreign substances.

What characterizes the second line of defense?

It includes inflammation and phagocytosis and acts rapidly once the first line is overcome.

What is unique about the third line of defense?

It is acquired on an individual basis as each foreign substance is encountered by lymphocytes.

What is the importance of cytokines in immunity?

Cytokines are signaling molecules that regulate immune responses; one pro-inflammatory cytokine is IL-6, and one anti-inflammatory cytokine is IL-10.

What are antigens or markers?

They are molecules on cell surfaces that help the immune system identify self versus nonself.

What is the function of white blood cells in the immune system?

They constantly move throughout the body to recognize and differentiate between self and foreign material.

What are PAMPs?

Pathogen-associated molecular patterns that are common markers found on many different microbes.

What are PRRs?

Pattern recognition receptors used by host cells to recognize PAMPs in innate immunity.

How does the immune system promote surveillance?

It exists as a complex network of cells and fluids that permeate every organ and tissue.

What is the mononuclear phagocyte system (MPS)?

A system in direct contact with tissue cells and extracellular fluid, playing a role in innate immunity.

What is the primary function of the lymphatic system?

To provide a route for the return of extracellular fluid to the circulatory system and to render surveillance against foreign materials.

What is lymphatic fluid?

A plasmalike liquid that transports white blood cells, fats, cellular debris, and infectious agents.

What are primary lymphatic organs?

Sites of immune cell birth and maturation, including red bone marrow and thymus.

What is the role of the thymus in immunity?

It is the site of T-cell maturation, where naïve T lymphocytes develop specificity.

Where are lymph nodes typically located?

In clusters along lymphatic channels and large blood vessels, such as in the armpit, groin, and neck.

What happens to lymph nodes during infection?

They may enlarge, providing clues to a physician about a patient's condition.

What is the connection between the lymphatic and circulatory systems?

Lymphatic vessels transport lymph back to the circulatory system, facilitating fluid balance and immune responses.

What is the significance of the immune system's ability to evaluate macromolecules?

It is central to distinguishing between self and nonself, preventing autoimmune disorders.

What are the secondary lymphatic organs?

Sites of immune cell activation and functioning, including lymph nodes, spleen, and various lymphoid tissues.

How does lymph flow through the body?

Lymph moves only through the contraction of skeletal muscles.

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

It is the most common method of destruction for cells identified as threats.

What is the role of the immune system in relation to foreign materials?

It is responsible for the surveillance, recognition, and destruction of foreign entities.

What is the function of lymphatic vessels?

They transport lymph and are similar to thin-walled veins, extending throughout the body.

What is the importance of the red bone marrow in immunity?

It is the site of blood cell production and the maturation of B lymphocytes.

What happens to T lymphocytes after maturation in the thymus?

They are released into circulation and migrate to lymph nodes and the spleen.

What is the role of the spleen in the immune system?

It acts as a secondary lymphatic organ involved in filtering blood and activating immune responses.

What is the primary function of the spleen?

To filter blood, removing worn-out red blood cells and pathogens.

What happens to asplenic adults compared to children who have had their spleen removed?

Asplenic adults can live relatively normal lives, but children are severely immunocompromised.

What are associated lymphoid tissues?

Discrete bundles of lymphocytes located at various sites beneath the skin and mucosal surfaces.

What is the function of skin-associated lymphoid tissues (SALT)?

To provide an effective first line of defense against microbes entering through the skin.

What does gut-associated lymphoid tissue (GALT) include?

Appendix, lacteals, and Peyer's patches.

What are the main components of whole blood?

Blood cells (formed elements) suspended in plasma.

What is hematopoiesis?

The production of blood cells.

What are cytokines?

Small active molecules secreted to regulate various aspects of cell development, inflammation, and immunity.

What are histiocytes?

Differentiated macrophages and dendritic cells that reside permanently in tissues.

What is the first line of defense in the immune system?

Inborn, nonspecific physical and chemical barriers that impede the entry of microbes.

How does the skin serve as a barrier to pathogens?

Through the tough outer layer (stratum corneum) and constant shedding of skin cells.

What role do mucous membranes play in immunity?

They impede entry and attachment of bacteria and flush out pathogens through secretions.

What is the ciliary escalator?

A mechanism in the respiratory tract that conveys trapped particles in mucus toward the pharynx.

How do vaginal secretions contribute to immunity?

They provide cleansing of the lower reproductive tract.

What is microbial antagonism?

The process by which normal microbiota block access of pathogens to epithelial surfaces.

What are the four major categories of nonspecific immunity?

Phagocytosis, inflammation, fever, and antimicrobial products.

What is the role of neutrophils in the immune response?

They are general-purpose phagocytes that react early to infections and tissue damage.

What happens to monocytes after they migrate into tissues?

They transform into macrophages.

What is the function of lysozyme?

An enzyme that hydrolyzes peptidoglycan in bacterial cell walls, found in tears and saliva.

What is the significance of hydrochloric acid in the stomach?

It serves as a chemical barrier against pathogens.

What is the flushing effect of sweat?

It helps remove microbes from the skin surface.

What is the role of the appendix in immunity?

It is part of the gut-associated lymphoid tissue (GALT) that contributes to immune function.

What is the primary component of pus?

Neutrophils, which are a sign of bacterial infection.

What is the function of the stratum corneum?

To act as a tough, waterproof barrier against pathogens.

What are Peyer's patches?

Compact aggregations of lymphocytes in the ileum of the small intestine.

What are the effects of barrier loss in the immune system?

Increased susceptibility to infections, especially in patients with severe burns.

What is the role of macrophages in the immune system?

To ingest and eliminate microbes and extract immunogenic information.

Name two types of macrophages found in the lungs.

Alveolar macrophages.

What is phagocytosis?

The physical process of engulfment and destruction of foreign cells by phagocytes.

List the events of phagocytosis in order.

Chemotaxis, adhesion, ingestion, phagosome formation, phagolysosome formation, destruction, excretion.

What are pathogen-associated molecular patterns (PAMPs)?

Signal molecules found on microbial surfaces recognized by phagocytes.

What role do pattern recognition receptors (PRRs) play in the immune response?

They recognize and bind PAMPs on phagocytes and other immune cells.

What are the classic signs of inflammation?

Rubor (redness), calor (warmth), tumor (swelling), dolor (pain), and loss of function.

What are the chief functions of inflammation?

To mobilize immune components, repair tissue damage, and destroy microbes.

What is diapedesis?

The migration of white blood cells out of blood vessels into tissues.

What is chemotaxis?

The migration of cells in response to a specific chemical stimulus.

What is the significance of edema in inflammation?

It dilutes toxic substances and helps trap microbes to prevent their spread.

What is a pyogenic bacteria?

Bacteria that stimulate the formation of pus, such as streptococci and staphylococci.

What is a fever?

An abnormally elevated body temperature, often a symptom of infection.

What are exogenous pyrogens?

Substances from infectious agents that induce fever by resetting the hypothalamic thermostat.

What are the benefits of fever?

Inhibits microbial growth, impedes bacterial nutrition, and stimulates immune reactions.

What is interferon?

A small protein produced by cells that helps inhibit viral replication and modulate immune responses.

What is the complement system?

A group of over 30 blood proteins that work together to destroy pathogens.

What is the membrane attack complex (MAC)?

A structure formed by the complement system that creates pores in pathogen membranes, leading to cell lysis.

What are antimicrobial peptides?

Short proteins that can insert into bacterial membranes and create pores, leading to cell lysis.

What are host restriction factors?

Molecules produced by host cells that limit viral replication inside the host.

How do macrophages contribute to gut health?

They are essential for establishing the correct gut microbiota and maintaining microbial diversity.

What factors can elicit inflammation?

Trauma from infection, tissue injury, necrosis, and specific immune reactions.

What is chronic inflammation?

A prolonged inflammatory response that can lead to diseases such as cardiovascular disease.

What is the role of inflammasomes?

They recognize PAMPs within phagocytic cells and initiate inflammation.

What is the relationship between aging and inflammation?

Some researchers believe that aging may be a consequence of increasing inflammation in multiple body systems.

What is the role of neutrophils in inflammation?

They aggregate at the inflamed site to phagocytose and destroy bacteria and dead tissues.

What is the significance of leaky blood vessels during inflammation?

They allow fluid and immune cells to enter tissues, which is essential for fighting infection.

What is a fever of unknown origin (FUO)?

A fever with no identifiable cause.

What are endogenous pyrogens?

Substances released by immune cells during phagocytosis that induce fever.