How can we help?

You can also find more resources in our Help Center.

Ch. 18 - Host Defenses against Microbial Infection

STUDY
PLAY
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