Ch. 18 - Host Defenses against Microbial Infection

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Host defenses confine microbial growth to the _____ surfaces of the body.

outside

_____ is a dynamic process, as microbes continually breach the barrier of skin and mucous membranes.

Defense

In animals, a state of health is characterized by near _____ of the deep tissues, the lungs, the bladder, and the uterus.

sterility

The most heavily colonized area is the mucous membranes and luminal space of the _____ _____. (microbial densities of 10^11 cells per milliliter)

intestinal tract

The _____ is lightly colonized over most of its surface - about 10^7 bacteria per cm^2.

skin

the normal flora is usually _____ to the host.

protective

The evolutionary process has been one of _____.

coadaptation

Macroscopic and microscopic symbionts are continuously selected for _____ that make their association more stable, sustainable, and less harmful.

adaptations

Every healthy plant and animal carries hundreds of different types of _____.

microorganims

The collection of microbes on a human that usually protects them is called the _____ ______.

normal flora (resident flora)

Normal flora prevent the body from being colonized by other, less benign, _____.

parasites

Germ-free organisms are much more _____ to infections than their natural counterparts.

susceptible

The normal flora occasionally causes _____.

disease

_____ _____ may become serious pathogens if they get to other areas of the body. (UTIs; Klebsiella pneumoniae and E. coli)

Normal flora

Some normal flora can be serious pathogesn in their normal niche if _____ allow them to proliferate to a greater than normal extent. (Strep throat)

conditions

_____ immunity is always active.

Innate

_____ immunity is specifically induced by exposure to an invader.

Adaptive

Many defenses are _____ including barriers (skin, mucous membranes) or activities (lung function, flowing liquids).

mechanical

Fluid sweeps most of our cells, the mechanical action of this flowing liquid helps limit the niches that _____ have for colonization.

pathogens

What are two way pathogens with stand the flow of liquid?

biofilms
attachment

Some _____ are sequestered in the cells of the animal body.

nutrients

Nutrients within cells are not available to invading microbial cells unless a pathogen has the ability to _____ host cells to release the nutrients.

lyse

What nutrients can pathogens steal from host cells and what is difficult to get?

glucose and amino acids are readily available.
Iron is tightly sequestered. It can be gotten from transferrin and through hemolysis (of RBCs)

_____ prey on invading microbes.

Phagocytes

_____ is the killing, and digestion of invading microorganims.

Phagocytosis

The major types of cells whose function includes phagocytosis are _____ (a form of lymphocyte) and _____ _____ (a form of leukocyte or white blood cell).

macrophages
polymorphonuclear neutrophils (PMNs)

_____ _____ are found mainly in the blood but leave the blood and migrate to the site of active infections during the process of inflammation.

Polymorphonuclear neutrophils

_____ are short-lived cells that are continually replaced, lack mitochondria, and depend on fermentation of glucose.

PMNs

_____ are found virtually everywhere within the body (wandering vs. fixed).

Macrophages

_____ are long-lived cells, have mitochondria, have an oxidative metabolism, and present antigens.

Macrophages

Both _____ and _____ move by amoeboid motion and actively seek out invading microbe.

PMNs and macrophages

After ingesting invading microbes, a specialized killing sequence of reactions is initiated - _____ _____.

oxidative burst

In an oxidative burst (which requires aerobic conditions), the phagocyte produces a series of toxic _____ compounds designed to kill the phagocytosed prey.

oxygen

_____ _____ cells destroy virus-infected host cells.

natural killer

_____-_____ cells are recognized by the viral glycoproteins tha appear on their surface.

Virus-infected

When a natural killer cell encounters a virus-infected cell, how does the NK cell kill it?

It binds tightly to it and secretes perforin that dissolves into the target cell membrane and forms a pore through which granzymes diffuse and activate apoptosis.

____ peptides of many kinds are found in all animals.

Antimicrobial

A variety of different tissues secrete antimircrobial proteins which are _____ defenses.

innate (constitutive)

Give the two classes of antimicrobial 'proteins.'

enzymes
antimicrobial peptides (defensins)

Antimicrobial enzymes include _____, an enzyme that hydrolyzes murein, and _____ that hydrolyze the ester linkages in phospholipids.

lysozyme and phospholipases

_____ ______ are present on nearly all body surfaces andi n all of the tissues.

antimicrobial peptides (AMPs)

_____ _____ are amphipathic so they separate regions of polar and nonpolar amino acids and they have an affinity for membranes.

Antimicrobial peptides

Some _____ _____ proteins aggregate to form a pore or dissolved ones interfere with lipid packing.

antimicrobial peptides

_____ are another category of protective proteins that enhance the binding of the phagocyte membrane to the microbe to be phagocytosed.

Opsonins

_____ host defenses include inflammation, interferon, and RNA interference.

Adaptive (inducible)

The best known of the adaptive defenses is the _____ _____.

immune system

_____ increase host defenses at the site of inflections.

Inflammation

With _____, the redness is due to dilation of the capillaries that brings increased blood flow to the site of infection.

inflammation

With inflammation, the _____ is due to increased leakiness of the capillaries, which allows serum (carrying antimicrobial peptides) to leak into the infected tissue.

swelling

With inflammation, the _____ is formed of large numbers of dead phagocytic cells tha invaded the tissue in search of microbial cells.

pus

Initiation of inflammation is via the ____ system.

innate

The key player in the innate system is __.

C3

Most of the C proteins are made primarily in the _____.

liver

There is a low level of continuous hydrolysis of C3a and C3b in the _____.

blood

Which C protien binds to surface bacteria and viral proteins and includes LPS, teichoic acids, surface proteins with highly repetitive structures?

C3b

Which C protein activates mast cells releasing histamine (vasodilation and increase permeability of capillaries), heparin (anticoagulant), and cytokines (chemoattractants).

C3a

_____ reduces the ability of viruses to spread.

Interferon

Interferon is induced by _____ that is not a normal product of our metabilism but is typically a viral intermediate.

dsRNA

When inducing the interferon, _____ is secreted by "infected" cell and taken up by that cells neighbor shutting down their protein synthesis and it has a dual mechanism of action.

dsRNA

The _____ system recognizes only foreign molecules.

immune

The immune system targets foreign materials or _____, including virions, virus-infected host cells, bacterial or protozoal pathogens, and protein toxins produced by pathogens.

antigens

The immune system of each individual must learn not to target native molecules - called _____.

tolerance

The immune system has two principal branches that target invaders by separate _____.

mechanisms

_____ immunity is mediated by a class of soluble proteins termed antibodies.

Humoral

_____ possess highly specific binding sites that can attach the antibody to the bacterial cell or a virus. They can also bind to small regions of soluble proteins.

Antibodies

A antibodies are characterized by having more than one identical binding site at the tips of their _____.

arms

T/F: Each arm of an antibody is composed of two different protein subunits and both subunits are involved in forming the binding site.

True

Antibodies bind to _____.

antigens

T/F: Most antigens have many different sites on their surface to which an antibody can bind.

True

Each of the specific site on an antibody where an antigen can bind is termed an _____.

epitope

Antibody binding to antigens protects by enhancing _____ and by preventing antigen entry into the host cells.

phagocytosis

If antibodies bind to epitopes at or near the site that interacts with the receptors, the presence of the antibody can then block the binding to host cells, thus _____ the virion or toxin.

neutralizing

Antibody binding activates the _____ system.

innate (complement)

When C3b accumulates on the surface of the invading cells, it initiates a series of reactions ending in the formation of the _____ _____ _____/

membrane attack complex

The membrane attack complex is a pore through the membrane formed by complement/innate proteins, which makes the membrane _____ and kills the cell.

leaky

The _____ _____ ____ is effective in killing pathogens without a substantial wall or with a relatively thin wall.

membrane attack complex

Antibody-producing cells are generated by a process of _____ selection.

clonal

During embryonic development of the immune system, the developing fetus produces precursors of antibody producing cells, called ___ _____.

B cells

In B cell differentiation, recombination events occur between the different antibody genes and there is a nearly infinite variety of different recombination events. The result is that a great diversity of different cells are produced, each of which has a different _____ gene.

antibody

B cells that express antibodies to native epitopes are _____ during the developmental process.

killed

After exposure to a particular epitope, the body has hundreds of times more ___ _____ with that particular epitope specificity than before.

B cells

A second exposure to the same epitope results in a very rapid production of high levels of _____. This is the basis of the secondary response and of immunological memory.

antibody

Induction of B-cell multiplication requires bound antigen and ____ _____ _____.

Helper T cells

_____ _____ cells have the principal role of stimulating the multiplication of B cells when their cognate epitope is present.

Helper T cells

Helper T cells recognize B cells via a system that includes two principal membrane proteins: _____ _____ _____ on the B cell and _-____ _____ on the TH cells.

major histocompatibility complex II (MHC II)
T-cell receptors (TCRs)

TH cells role is to recognize foreign peptides bound in _____.

MHC II

A TH cell can bind to a B cell only if the peptides displayed by MHC II on its surface are foreign and match the _____ specificity of the TH cell's receptor.

epitope

Cell-Mediated immunity is a _____ defense.

adaptive (inducible)

Cell-mediated arm of the immune system complements humoral immunity and is particularly important in combating _____ infections.

viral

Cell-mediated immunity is mediated by specific cells termed _____ ____ _____.

cytolytic T lymphocytes or CTLs

_____ target cells that are making foreign proteins.

CTLs

CTLs recognize their targets using a different form of major histocompatibility complex protein on the surface of the target cell, termed MHC I, and _-_____ _____ on the CTLs.

T-cell receptors

______ is membrane protein with a groove on its external portion in which are bound peptides derived from intracellular proteins.

MHC I

_____ are found on all nucleated body cell - infected or cancerous cells have foreign antigens that will be displayed with this on the surface of the cells and they are recognized by cytotoxic T cells.

MHC I

_____ are found on macrophages, B cells and dendritic ells; they will bind to antigens derived from ingested microbes (phagocytosis, digestion, antigen presentation) and they are recognized by helper T cells.

MHC II

If a cell is infected bu a virus, some _____ molecules will display peptides that are foreign and these peptides can be recognized by the CTLs.

MHC I

CTLs and TH cells are produced by a process of _____ _____ similar to the production of B cells.

clonal selection

Much of the immune system activity occurs in _____ _____.

lymph nodes

_____ _____ are specialized organs that filter the flowing lymph and that scan it for foreign material.

Lymph nodes

Lymph nodes contain a large portion of the body's _____ _____ cells and _____ cells.

memory B cells
T cells

Lymph nodes are a principal site for _____ system activation.

immune

______ is a deliberate stimulation of the immune system.

Vaccination

The first efforts to evoke immunity were to prevent serious cases of _____.

smallpox

Smallpox disease was deliberately transmitted usually by scratching some material from a pustule on someone with active smallpox into the skin of the recipient. This was called _____

variolation

Variolation usually caused a much _____ serious disease that naturally acquired smallpox.

less

Who dealt with coxpox and vaccination?

Edward Jenner

The development of _____ was one of the major advances in the history of medicine.

vaccination

______ is the deliberate infection of people with a virus evoked immunity to a related, but much more serious virus.

Vaccination

_____ may be live or dead organisms or inactivated toxins.

Vaccines

Name the three principle ways of stimulating immunity.

Killed vaccines
live, attenuated vaccines
inactivated toxins

_____ vaccines consist of a mixture of all of the proteins, nucleic acids, and polysaccharides of the pathogen.

Killed vaccines

With killed vaccines, antibodies to all of the compounds are stimulated and most of the antibodies are ineffective because the antigens to which they bind are _____.

intracellular

_____ vaccines consist of pathogens whose virulence has been attenuated.

Live vaccines

Live vaccines have been reduced to a level where the cause infection but cause no _____ or only minor ones.

symptoms

_____ is done by allowing the virus to replicate for many generations in nonhuman organisms or tissue culture with nonhuman cells. During the multiplication, the virus adapts to its new host and becomes less adapted to multiplying in humans.

Attenuation

A major advantage of _____ vaccines is that they can spread to unvaccinated people.

live

Using toxin molecules that have been denatured called ____, can stimulate the production of antibodies that can bind to and neutralize the native toxin.

toxoids

_____ prevent the harmful effects of an infection, but do not prevent the infection itself.

Toxoids

The anthrax vaccine prevents the A and B subunits that make a toxin from associating and forming the toxin. What prevents the association?

Anti-B

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