pathogens + immune system

Question 1

list the living organisms that can cause disease

Answer 1

bacteria, fungi, protozoa

Question 2

list acellular agents that can cause disease

Answer 2

viruses, viroids, prions

Question 3

what is a viroid pathogenic to

Answer 3

plants

Question 4

what are viroids composed of

Answer 4

small, circular RNA

Question 5

T or F: viroids encode proteins

Answer 5

false; even though they’re RNA, they don’t encode proteins

Question 6

how do viroids replicate

Answer 6

using a host cell enzyme

Question 7

structure of viroid

Answer 7

nucleotides are often paired = RNA has a closed 3D structure

Question 8

how do viroids cause disease

Answer 8

by RNA silencing of host genes

Question 9

how were prions named

Answer 9

proteinaceous infectious particle

Question 10

what is a prion

Answer 10

an abnormally folded protein that can cause disease

Question 11

where are prions found within the human body

Answer 11

on the PM of neurons

Question 12

function of prions in humans?

Answer 12

unknown

Question 13

list the two ways in which a prion can stably fold

Answer 13

1. into the normal (cellular) form: PrpC
2. into the diseased (abnormal) form: PrPSc

Question 14

list 3 ways that diseases can occur due to prions

Answer 14

1. spontaneous conf change of the protein into the abnormal form
2. mutation in the gene that results in a conf change to the abnormal form
3. through ingestion/injection of the abnormal prion protein

Question 15

describe what happens when the body encounters one abnormal prion

Answer 15

chain reaction occurs. Abnormal prions cause normal ones to change into abnormal ones = build up of PrPSc in the brain = plaques = spongiform brain

Question 16

what are prion diseases known as

Answer 16

TSEs (transmissible spongiform encephalopathies)

Question 17

features of prion diseases?

Answer 17

can occur in humans and animals, fatal, long incubation period, no immune response, victims lose motor function/become demented/death follows

Question 18

list 3 animal TSEs

Answer 18

mad cow, scrapie, chronic wasting

Question 19

list 3 human TSEs

Answer 19

Kuru, fatal familial insomnia, Creuztfelt-jacob disease (CJD)

Question 20

describe CJD

Answer 20

most common human TSE, found among 55-75 year olds
symptoms: progressive dementia, visual/speech problems, tremors, moderate plaques, spongiform brain
incubation time is 3-20 years

Question 21

what are the three different forms of CJD

Answer 21

sporadic, familial, iatrogenic (caused by medical treatment)

Question 22

describe the new variant of CJD (nvCJD)

Answer 22

patients are younger and have larger plaques. It is the human form of mad cow disease

Question 23

list some ways that prions are NOT destroyed

Answer 23

boiling or cooking, standard autoclave sterilization, radiation, alcohol disinfectants (alcohol or aldehyde)

Question 24

list some ways that prions ARE destroyed

Answer 24

incineration (super high heat), high heat/pressure autoclaving, autoclaving with alkali

Question 25

T or F: some people are born with inherited immunodeficiency diseases

Answer 25

true

Question 26

what is X-SCID + what does it cause

Answer 26

an immunodeficiency disease; there’s a gene defect so you can’t make WBCs

Question 27

what are the two types of immune responses

Answer 27

innate and adaptive

Question 28

features of the innate response

Answer 28

it is present from birth
it provides a rapid response to a foreign substance
it’s a general response (no specificity)
does not have a memory response

Question 29

what two lines of defense is the innate response composed of

Answer 29

first and second lines of defense

Question 30

what is the first line of defense composed of

Answer 30

skin, mucous membranes, normal microbiota
(it’s the physical + chemical ways of protection)

Question 31

how does the skin protect us from infection (via physical means)

Answer 31

The outer layer consists of tightly packed keratinocytes which constantly shed, removing any microbes that have attached to them

Question 32

describe how chemical factors of the skin protect us

Answer 32

sweat from sweat glands flushes microorganisms off the skin. release of sebum from oil glands + secretions from sweat glands keep the pH of the skin low (5-6)
presence of lysozyme in sweat

Question 33

list physical ways that mucous membranes protect us

Answer 33

• epithelial cells are packed tightly + constantly replaced
• saliva dilutes microbes present + flushes them away
• lacrimal apparatus in the eye produces tears that flush them
• mucus traps microbes (present in mouth, coats the hairs of the nose)
• mucociliary blanket in lower resp tract traps microbes and moves them away from lungs
• peristalsis of intestines minimizes establishment of harmful microbes
• flow of urine in genitourinary tract prevents colonization

Question 34

list chemical ways that mucous membranes protect us

Answer 34

• lysozyme in nasal secretions, saliva, tears, urine
• IgA in saliva prevents attachment of microbes
• gastric juice in stomach
• vaginal secretions = acidic environment
• acidity of urine
• presence of lactoferrin in tears inhibit growth by sequestering iron
• production of lactoperoxidase which is responsible for production of superoxide radicals

Question 35

how can the normal microbiota protect us

Answer 35

inhibiting pathogens from colonizing through competition (use up nutrients, receptors, iron), bacteriocins are produced that are harmful to pathogens, alteration of the physical environment so pathogen cannot survive (ie pH, oxygen availability)

Question 36

what is the second line of defense composed of

Answer 36

cells (phagocytes) and antimicrobial chemicals (complement system)

Question 37

describe how cells in the second line of defense can protect us

Answer 37

they can engulf microbes (called phagocytes)

Question 38

list the different phagocytes in the blood

Answer 38

macrophages, dendritic cells, eosinophils, monocytes

Question 39

how do antimicrobial chemicals protect us in the second line of defense

Answer 39

the complement system is a group of 30 proteins found in the blood. Consequences of complement activation: inflammatory response, cytolysis, phagocytosis

Question 40

features of the adaptive immune response

Answer 40

it’s a specific response to a specific pathogen
it’s slower to respond
it has a memory response

Question 41

T or F: the innate and adaptive immune responses work independently

Answer 41

false; they do NOT work independently

Question 42

list the two branches of the adaptive response + what they use as weapons against pathogens

Answer 42

humoral immunity: uses antibodies
cell-mediated immunity: uses T cells

Question 43

describe humoral immunity

Answer 43

uses antibodies that are located in blood, mucus secretions, tears, saliva, breast milk. They act by binding to an antigen.
5 classes of antibodies: IgG, IgM, IgD, IgA, IgE

Question 44

list 4 ways that antibodies protect us from disease

Answer 44

agglutination, neutralization, opsonization, complement activation

Question 45

what is agglutination

Answer 45

phagocytes can engulf more pathogens

Question 46

what is neutralization

Answer 46

antibodies block adhesion of pathogens to host cell receptors

Question 47

what is opsonization

Answer 47

microbe is coated with antibody, thereby enhancing its ability to be recognized by a phagocyte

Question 48

what is complement activation

Answer 48

antigen-antibody binding can activate a component of the complement system which can lead to inflammation and cytolysis

Question 49

what are the two types of T cells in cell mediated immunity

Answer 49

cytotoxic T cells and helper T cells

Question 50

what do cytotoxic T cells do

Answer 50

directly kill an infected cell

Question 51

what do helper T cells do

Answer 51

provide help to Tc cells and B cells through the release of signaling molecules (cytokines). They’re needed for B cells to produce antibodies and for Tc cells to kill infected targets