pathogens + immune system Flashcards
list the living organisms that can cause disease
bacteria, fungi, protozoa
list acellular agents that can cause disease
viruses, viroids, prions
what is a viroid pathogenic to
plants
what are viroids composed of
small, circular RNA
T or F: viroids encode proteins
false; even though they’re RNA, they don’t encode proteins
how do viroids replicate
using a host cell enzyme
structure of viroid
nucleotides are often paired = RNA has a closed 3D structure
how do viroids cause disease
by RNA silencing of host genes
how were prions named
proteinaceous infectious particle
what is a prion
an abnormally folded protein that can cause disease
where are prions found within the human body
on the PM of neurons
function of prions in humans?
unknown
list the two ways in which a prion can stably fold
- into the normal (cellular) form: PrpC
- into the diseased (abnormal) form: PrPSc
list 3 ways that diseases can occur due to prions
- spontaneous conf change of the protein into the abnormal form
- mutation in the gene that results in a conf change to the abnormal form
- through ingestion/injection of the abnormal prion protein
describe what happens when the body encounters one abnormal prion
chain reaction occurs. Abnormal prions cause normal ones to change into abnormal ones = build up of PrPSc in the brain = plaques = spongiform brain
what are prion diseases known as
TSEs (transmissible spongiform encephalopathies)
features of prion diseases?
can occur in humans and animals, fatal, long incubation period, no immune response, victims lose motor function/become demented/death follows
list 3 animal TSEs
mad cow, scrapie, chronic wasting
list 3 human TSEs
Kuru, fatal familial insomnia, Creuztfelt-jacob disease (CJD)
describe CJD
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
what are the three different forms of CJD
sporadic, familial, iatrogenic (caused by medical treatment)
describe the new variant of CJD (nvCJD)
patients are younger and have larger plaques. It is the human form of mad cow disease
list some ways that prions are NOT destroyed
boiling or cooking, standard autoclave sterilization, radiation, alcohol disinfectants (alcohol or aldehyde)
list some ways that prions ARE destroyed
incineration (super high heat), high heat/pressure autoclaving, autoclaving with alkali
T or F: some people are born with inherited immunodeficiency diseases
true
what is X-SCID + what does it cause
an immunodeficiency disease; there’s a gene defect so you can’t make WBCs
what are the two types of immune responses
innate and adaptive
features of the innate response
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
what two lines of defense is the innate response composed of
first and second lines of defense
what is the first line of defense composed of
skin, mucous membranes, normal microbiota
(it’s the physical + chemical ways of protection)
how does the skin protect us from infection (via physical means)
The outer layer consists of tightly packed keratinocytes which constantly shed, removing any microbes that have attached to them
describe how chemical factors of the skin protect us
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
list physical ways that mucous membranes protect us
- 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
list chemical ways that mucous membranes protect us
- 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
how can the normal microbiota protect us
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)
what is the second line of defense composed of
cells (phagocytes) and antimicrobial chemicals (complement system)
describe how cells in the second line of defense can protect us
they can engulf microbes (called phagocytes)
list the different phagocytes in the blood
macrophages, dendritic cells, eosinophils, monocytes
how do antimicrobial chemicals protect us in the second line of defense
the complement system is a group of 30 proteins found in the blood. Consequences of complement activation: inflammatory response, cytolysis, phagocytosis
features of the adaptive immune response
it’s a specific response to a specific pathogen
it’s slower to respond
it has a memory response
T or F: the innate and adaptive immune responses work independently
false; they do NOT work independently
list the two branches of the adaptive response + what they use as weapons against pathogens
humoral immunity: uses antibodies
cell-mediated immunity: uses T cells
describe humoral immunity
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
list 4 ways that antibodies protect us from disease
agglutination, neutralization, opsonization, complement activation
what is agglutination
phagocytes can engulf more pathogens
what is neutralization
antibodies block adhesion of pathogens to host cell receptors
what is opsonization
microbe is coated with antibody, thereby enhancing its ability to be recognized by a phagocyte
what is complement activation
antigen-antibody binding can activate a component of the complement system which can lead to inflammation and cytolysis
what are the two types of T cells in cell mediated immunity
cytotoxic T cells and helper T cells
what do cytotoxic T cells do
directly kill an infected cell
what do helper T cells do
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
