21. 2 Barrier Defense and the Innate Immune Response

define innate immune response

relatively rapid but nonspecific and thus not always effective,

define adaptive immune response

slower in its development during an initial infection with a pathogen, but is highly specific and effective at attacking a wide variety of pathogens

what r barrier defenses in context of innate immune response

physical barriers that prevent pathogens from entering the body, destroying them after they enter, or flushing them out

what is the primary barrier to the entrance of microorganisms into the body

skin

how does the skin protect against pathogens

skins dry, keratinized epithelium inhibits bacterial growth, and shedding skin cells carry pathogens away, while sweat and skin secretions can lower ph, contain toxic lipids, and wash microbes away

what are the barrier defenses on the body

skin, sweat secretions on skin, oral cavity, stomach, mucosal surfaces, normal flora

what is the specific defense of the skin

epidermal surface

what is the protective aspect of skin

keratinized cells of surface, langerhans cells

what is the defense of the skin, mainly sweat secretions

sweat glands, sebaceous glands

what is the protective aspect of skin mainly sweat and secretions

low ph, washing action

what is the defense of oral cavity

salivary glands

what is protective aspect of oral cav

lysozyme

what is the defense of stomach

gastrointestinal tracti

what is protective aspect of stomach

lo ph

what is defense of mucosal surface

mucosal epithelium

what is protective aspect of mucosal surfaces

nonkeratinized eptihelial cells

what is defense of normal flora

mucosal tissue

what is protective aspect of normal flora

prevent pathogens from growing on mucosal surfaces

what is lysozyme

an enzyme that destroys bacteria by digesting their cell walls.

what is phagocyte

cell that is able to surround and engulf a particle or cell, a process called phagocytosis

role of phagocytes in immune systemm

The phagocytes of the immune system engulf other particles or cells, either to clean an area of debris, old cells, or to kill pathogenic organisms such as bacteria.

why phagocytes considered first line of defense

fast acting cells that defend against organisms that have breached barrier defenses and entered vulnerable tissues

what is role of phagocytes in immune system

destroy pathogens during innate immune responses by engulfing them through phagocytosis

what happens to pathogens after they are engulded by phagoctyes

pathogens r taken inside the phagocyte as a phagosome, killing many pathogens

what is phagosome

pathogens taken inside pahgocyte that fuses with a lysosome and its digestive enzyme

what are major pahocytes of immune system

macrophages, neutrophils, and dendritic cells

what is role of macrophages in immune system

particitpate in both innate and adaptive immune responses, moving though tissues and cooperatiing with lyphocytes

what is role of neutrophls in the immune syste,

attracted to infected tissues via chemotaxis and play a role in destroying pathogens during the inflammatory process

what bacteria causes tuberculosis and is hard clear from body

myocobacteria tuberculosis, resistant to enzymes and difficult to clear

how is macrophage shaped

irregular shaped that is amoeboid in nature and is most versatile of phagocytes in body

what are other examples of macrophages

kupffer cells in liver, histiocytes in connective tissue, and alveolar macrophages in lungs

how do macrophages exists

in many tissues of body, either freely roaming through connective tissues or fixed to reticular fibers within specific tissues such as lymph nodes

what r granulocytes

neutrophil cells that is a spherical cell, that contains cytplasmic granules, which in turn contain a variety of vasoactive mediates such as histamine

macrophages r what other type of cell

agranulocytes

what is agranulocytes

ffew or no cytpoplasmic granules

how do macrophages and neutropils differ

macrophages act like sentries, always on guard against infection, neutrophils can be thought of as military reinforcements that are called into a battle to hasten the destruction of the enemy.

which subdivision does neutropihil play key role in

both innate and adaptive immune response

what is a monocyte

circulating precursor cell that differentiates into either a macrophage or dendritic cell, which can be rapidly attracted to areas of infection by signal molecules of inflammation.

what cell type r macrophage and monocyte

agranulocyte

what cell type is neutrophil

granulocyte

where is the primary location for btoh neutrophil and monocyte

blood

what is location of macrophages

body cavs or organs

what is function of macro ahd neutrophil in innate immune resoonse

phagocytosis

what is function of monocyte in innate immune respnse

precursor of macrophage/dendritic cell

what is apoptosis

cell death

what is role of NK cells in immune system

induce apoptosis in cells infected with intracellular pathogens like viruses and obligate intracellular bacteria

how do NK recognixe infected cells

use surface receptors to recognize infected cells

what r the 2 mechanisms by which nk cells induce apoptosis

1.expressing fas ligand, which binds to fas molecules on infected cells, and 2. releasing perforins and granzymes

what is perforin

a protein that forms pores in the membranes of infected cells.

what is granzyme

protein-digesting enzyme that enters the cell via the perforin pores and triggers apoptosis intracellularly.

what is pattern recognition receptor (PRR)

membrane bound receptor that recognizes characteristic features of a pathogen and molecules released by stressed or damaged cells.

what is role of PRRs in innate immune system

enables innate immune response to recognize pathogens and initiate responses such as phagocytosis or cellular apoptosis

why is the variety of PRRs limited

by the need for specific genes to encode each receptor type and the finite surface area of the cell membrane

y must the innate system get by

only a limited number of receptors that are active against as wide a variety of pathogens as possible.

what r soluble mediators of the innate immune system

inc cytokines and chemokines, which r chemical signals that induce cells to change their physiological characteristics

what is the role of cytokines in cell comm

allow cells to communicate with each other over short distances inducing changes in the receiving cells physiology

what is the difference btween cytokines and chemokines

cytokins induces changes in cell physiology, while chemokines attract cells from longer distances through chemotaxis

what is chemokine

soluble chemical mediator similar to cytokines except that its function is to attract cells (chemotaxis) from longer distances.

what are early induced proteins

proteins taht r not constitutively present in body but r made as needed during innate response

what is role of interferons

proteins secreted by virus infected cells that induce adjacent cells to make antiviral proteins, protecting them from infection

what is oponsinzation

tagging of a pathogen for phagocytosis by binding of an antibody or an antimicrobial protein

how does oponsination enhance phagocytosis

brings the pahgocyte and bacterium into close promiximity, enhancing phagocytossis by allowing phaogcytes to recognize and bind to teh tagged pathogen

what is complement system

is a series of proteins constitutively found in the blood plasma. As such, these proteins are not considered part of the early induced immune response, even though they share features with some of the antibacterial proteins of this class.

what r functions of complement system

oponsinzation, chemotaxis, and forming pores in the plasma membrane of pathogens

what is the difference between teh classical and alternate pathways of complement activation

requires antibodies of the adaptive immune repsonse, while the alternate pathway does not require antibodies to become activated

what is early induced response

rapid response to inection or inhyrt, characterized by the production of proteins and activation of immune cells, provifind immediate defense against pathogens

where is complement system made

in liver

once activated, the complement system is irreversible and releases fragments with the following actions:

• Bind to the cell membrane of the pathogen that activates it, labeling it for phagocytosis (opsonization)

• Diffuse away from the pathogen and act as chemotactic agents to attract phagocytic cells to the site of inflammation

• Form damaging pores in the plasma membrane of the pathogen

what is the common step in both the classical and alternate athways of comolenebt activation

splitting of the C3 proteins

what is the role of C3B in the complement cascafe

C3b binds to surface of pathogens, activating the rest of the cascade and oponsinizing the pathogen for phagocytosis

what is the function of the membrane-attack complex (MAC)

MAC forms pores in the plasma membrane of pathogens, disrupting their osmotic balance and killing them

how does the classical pathway differ from teh alternative pathway

requires presence of antibody bound to antigen, making it dependent on the adaptive immune response, whereas the alternate pathway does not

What is the hallmark of the innate immune response?

Inflammation is the hallmark of the innate immune response.

What are the four main characteristics of inflammation?

Heat, redness, pain, and swelling. (Loss of function is sometimes considered a fifth.)

Does inflammation always need an infection to start?

No, inflammation can be caused by tissue injury alone, without infection (e.g., hitting your thumb with a hammer).

What happens when tissue is damaged and inflammation occurs?

Phagocytic cells are brought to the damaged area to clear debris and start wound repair.

What two main things does the inflammatory response accomplish?

It destroys pathogens and removes debris, while isolating the infection site to limit spread.

What is acute inflammation? (Define it)

Acute inflammation is a short-term inflammatory response to an injury or insult to the body.

What is chronic inflammation? (Define it)

Chronic inflammation is ongoing, long-term inflammation that happens when the cause is not resolved. It is associated with major tissue destruction and fibrosis.

What are some causes of chronic inflammation?

Chronic inflammation can be caused by foreign bodies, persistent pathogens, or autoimmune diseases like rheumatoid arthritis.

What are the four important parts of the inflammatory response?

Tissue injury, vasodilation, increased vascular permeability, and recruitment of phagocytes.

What happens during tissue injury in inflammation?

Injured cells release signals that stimulate mast cells to release inflammatory mediators like histamine, leukotrienes, and prostaglandins.

What is a mast cell? (Define it)

A mast cell is an immune cell that stores inflammatory chemicals in granules and releases them during injury to trigger inflammation.

What does histamine do during inflammation? (Define it)

Histamine is a chemical released by mast cells that increases blood vessel diameter (vasodilation) and permeability, leading to swelling.

Besides mast cells, what other cells release inflammatory mediators?

Injured cells, phagocytes, and basophils.

What do leukotrienes do during inflammation?

Leukotrienes attract neutrophils to the injury site by chemotaxis and increase vascular permeability.

What do prostaglandins do during inflammation?

Prostaglandins cause vasodilation and are major contributors to pain.

How do nonsteroidal anti-inflammatory drugs (like aspirin) help with inflammation?

They relieve pain by inhibiting prostaglandin production.

What is vasodilation?

The widening of blood vessels, increasing blood flow to the inflamed tissue.

What causes vasodilation during inflammation?

Inflammatory mediators like histamine cause vasodilation.

What two symptoms of inflammation are mainly due to vasodilation?

Heat and redness.

What is increased vascular permeability?

It is the leakage of fluid from blood vessels into the tissue, causing swelling (edema).

What is the role of leukotrienes in recruiting phagocytes?

They attract neutrophils to the site of infection or injury.

Which cells are the first to arrive at the site of inflammation?

Neutrophils.

What happens after neutrophils arrive at the inflammation site?

Macrophages are recruited to clean up debris.

What does the accumulation of dead neutrophils and debris create?

Pus at the infection site.

Why is inflammation valuable to the body?

It kills pathogens, removes debris, allows clotting factors to start wound repair, and helps initiate the adaptive immune response by transporting antigens to lymph nodes.