lecture 6- host defence and immunity Flashcards
resident biota
human body contains many habitants
-same body part can harbour different (but stable) communities at different times
Microbiota:
The community of microbes that lives in a specific part of the body
-bacteria, archaea, eukarya, VIRUSES
microbiome
The collection of organisms, their genomes and genes
-microbial ecosystem understood through genetics
Skin Microbiota
Acquisition: starts in birth canal and continues through environment (interaction c/ microbes is good - form immunity)
- Variety of Environments
- Acidic pH (pH 4-6)
- High in Salt, low water
Organisms: Resident -Staphylococcus app Transient -Propionibacterium acnes Anaerobic -Haemophillus spp. -Mycobacterium spp. -Bacillus spp. (usually from soil) -Candida spp. (eukaryotic yeast)
The eye microbiota
acquisition: the environment
- harsh environment for bacteria d/t constant flushing and lysozyme in tears
-transient bacteria Usually skin flora: S. epidermidis And various diphtheroids
E. Coli
Klebsiella
Proteus
environmental contact c/ microbes cause Diseases:
S. pneuomoniae
H. Influenzae
Various virus’
microbiota: oral and nasal
Acquisition:
Birth canal, caregiver contact, Food, water, and fingers.
-protection:
Saliva, lysozyme
Cutaneous tissue
Immune surveillance
resident and transient microbes
Birth: Neisseria spp. (non-pathogenic) Streptococcus Spp. Actinomyces Spp. Lactobacillus Spp.
Teeth: Prevotella Fusobacterium S. mutans S. salivarius (500+ sp.)
resident microbes
benefit host - help us do things
transient microbes
non-essential; may be pathogenic
why do dentists often administer antibiotics to its with a heart murmur?
S. aureus, S. epidermis are residents in mouth. Direct connection from mouth to heart c/ arteries and veins increase the change of these microbes getting into blood
-pt c/ murmur have pooling blood in heart where bacteria could grow
Microbiota: respiratory
unsure of acquisition
- all microbes are transient
- have “mucocilary escalator” to bring out foreign substance.
-Biolfilm formers: S. pneumoniae P. aeruginosa H. influenzae K. pneumoniae
what micro was responsible for cystic fibrosis
p. auruginosa
lower Gi tract anatomy consists of?
Stomach Duodenum Ileum Jejunum Colon Ascending Transverse Descending -7 different types of cells for absorption, protection, ect. Environment is extremely diverse throughout the gi tract
microbiota: stomach
Acquisition: As a fetus, baby formula, food & water, tasting their environment.
-protection: Acidic Environment (pH ~2-4)
- resident and transient bacteria
- Helicobacter pylori and its role in gastritis and peptic ulcer disease was discovered by drinking bacteria, producing ulcer , treating it
V.cholerae (pathogenic) – killed at pH 4 (if malnourished pH rises and this pathogen can cause disease)
culture independent method?
NGS
microbiota: the intestines
Duodenum (pH 8)
10 000 microbes
Jejunum (pH 8)
10^7 mm^3
Ileum & Colon (pH 5-7)
1011 / gram of faces
*over 1000 species
microbiota: urogenital
acquisition - surrounding external environment (usually comes in backwards - not through kidney)
protection: constant flushing
Transient (most) Aerobic residents (some)
distal urethra:
S. epidermidis
Enterococcus spp.
Ecosystem
composed of communities (exchange c/ each other and their abiotic environment)
-stble ecosystems provide benefits (O2 production, water filtering, vitamin production)
meta-organism
human body
-co-evolved with specific communities of microbes: help us grow and develop
host-microbe interactions : -maintains community of commensals and symbionts
- helps prevent establishment and expansion of pathogens
- supports healthy function of metabolic processes
commensal organisms
-can be opportunistic but they only take / we supply them they don’t give anything back
symbionts
mutualistic relationship
how do microbiota differ between humans?
differs
why does the micro biome differ between body parts?
Particular niche requirements (ex: oxygen, pH, sugar, etc.)
Extracellular components that interact with receptors in host
explain the three basic steps of pathogen-human interaction
- contact
- infection
- disease
infection
A condition in which pathogenic microbes penetrate host defences, enter tissues and multiply
infectious disease
disruption of tissue or organ (pathologic state) caused by microbes or their products
pathogen
Parasitic relationship with its host; results in infection and disease (in susceptible individuals)
what does type and severity of infection depend on (4)
- Pathogenicity of the organism
- Dose
- Condition of the host
- Portal of entry
pathogenicity
an organism’s potential to cause infection or disease
true pathogens
- lifestyle depends on infecting the host
- Attack healthy people
- Infection made worse by a weak or immature immune system
opportunistic pathogens
Only cause disease when given opportunity (decreased immunity)
what is the process of infection?
- establishment
- spread
- disease effects
5 patters of infection
- Localized
- Systemic
- Focal
- Mixed
- Primary - Secondary
necrosis
accumulated damage leads to cell death and tissue death
localized infection
- pathogens stay local to where it began
* most common
systemic infection
pathogens spread to multiple sites and tissues through blood stream (usually)
Ex) viral infections (HIV, chickenpox)
- Salmonella enterica serovar Typhi
- causes typhoid fever
- Invade intestinal epithelium, spreads to macrophage, can become resident in gall bladder
focal infection
infectious agent (toxin) leaves local infection and goes to other areas but pathogen stays local
ex) Streptococcal pharyngitis
Bacteria in throat (“Strep throat”)
-Antibodies against bacterial cell wall also attack other tissues, such as heart and joints
-ex) dental infection going to heart
mixed infection
-Multiple species contribute to infection
Example: dog bite
all sorts of different bacteria enter the wound
-Can be called “polymicrobial” disease
primary-secondary infection
- Successive
- Can occur due to weakened immunity
- Localized or systemic
Example:
Child scratches chickenpox (primary)
Then gets a localized Staphylococcus aureus infection (secondary)
-UTI eats to vaginal infection
sign
any objective evidence of disease as noted by an observer
symptom
the subjective evidence of disease as sensed by the patient
syndrome
when a disease can be identified or defined by a certain complex of signs and symptoms
Signs and Symptoms of infectious disease
signs: fever, septicemia, microbes in tissue fluids, chest sounds
symptoms: chills, pain, aches, soreness, irritation, malaise, fatigue
septicemia
microorganisms are multiplying in the blood and are present in large numbers
ex)meningitis – divides within 20 mins and can kill a pt within 24 hours
bacteremia
microbes are present in the blood but are not necessarily multiplying
*NO Signs of septicaemia - still dangerous
first line of defence
physical and chemical barriers - skin, cilia, mucous, secretions, resident microbiota
- Innate and nonspecific
- doesnt improve c/ exposure
second line of defence
inflammation, phagocytic white blood cells
- innate and non-specific
- communicate c/ third one defence
third line of defence
recognition of infectious agents (memory)
-B cells and T cells
Antibodies
- slower b/c has to be specific to pathogen –> develop this by experience and contact c/ microbes
- communicates c/ 2nd line
macrophage
immune cell
- eats foreign particles and displays on cell membrane
- asks T and B cells if they are foreign or not
how are the lungs nearly bacteria free if you breath in many microbes c/ each breath
first line of defence!
-Mucus, cilia, and macrophage
what are nonspecific chemical defences?
-Sebaceous secretions
-Lysozyme in tears (attacks bacterial cell wall)
-Lactic acid and electrolyte concentrations of sweat
-Skin’s acidic pH and fatty acid content
-HCl in the stomach
-Digestive juices and bile in the intestine
(break down membranes and denature proteins)
-Acidic pH in the vagina
3 components of innate immunity
- Antimicrobial proteins
- Antimicrobial peptides
- White blood cells (leukocytes)
immunology
the study of all features of the body’s second and third lines of defense
what does healthy immune system do?
- Surveillance of the body
- Recognition of foreign material
- Destruction of foreign entities
auto-immune disease
immune system makes a mistake and attacks body itself
ex) MS –> (possibly viral)
- autoantibodies attack myelin sheath in brain
hoe do cells distinguish between self and foreign particles
2nd & 3rd line do this
- Evaluate cells by examining markers on their surfaces (proteins)
- body identifies cancerous cells as damaged “self” = foreign and they want to destruct
compliment system
26 blood proteins that work together to destroy bacteria and certain viruses
-1 protein activates 2 more –> chain reaction to destroy infection
antimicrobial peptides (defensins)
- composition
- function
- location
- composed of 18-45 amino acids (small)
- Made by neutrophils and epithelial cells
- Active against bacteria, fungus, and enveloped viruses –> poke holes into bacteria causing death
- located on fingertips, stomach, vagina, armpits, nose, ect.
antimicrobial proteins: cytokines
signal for help (tell cells to come help or cell to self destruct)
- secrete chemical signals
- mediate inflammation
Interferons
involved in fight against viruses, other microbes, in immune regulation and communication
- Bind to cell surfaces and induce changes in gene expression (making them undergo cell suicide)
- viruses that come out of dormant stage and begin to divide are often controlled by these cells
what types of white blood cells are most abundant in second line of defence?
Neutrophils: Phagocytize bacteria (engulf it)
-First to arrive during an immune response (attracted by cytokines)
Eosinophils: Attach and destroy eukaryotic pathogens
- little bags of degradative enzymes
- Associated with inflammation and allergies (see pollen, cat hair as foreign cause unnecessary inflammatory response)
neutrophils
WBC
-surface granules contain digestive enzymes
-First to arrive during an immune response (inflammation)
-Attracted to wound d/t citokines–> Move from blood to wound when adhesion molecules hit “STOP” light
Hunt for invaders –> engolf
how do WBC get from the blood to the site of infection
Diapedesis
- White blood cells have special ability to cross tissue barriers
- attracted by chemotaxis (cytokine immune signal)
- hit the “STOP” signal in blood then travel through tissue (diapedesis) following chemotaxis to site on infection
T cells
cell-mediated immunity
-monocytes that arise from thymus
B cells
antibody-mediated immunity
-monocytes that arise from bone marrow
- Macrophage presents antigen to B cells
- ->reacts to it and produces antibodies specific to that antigen
Macrophages
mature monocytes
long lived and can multiply
Innate response
- Many specific and nonspecific phagocytic and killing functions
- Mop up infections (phagocytosis)
- Full of digestive enzymes
reticuloendothelial system
- Network of connective tissue fibers
- Provides a passageway within and between tissues and organs
- White blood cells move through these corridors
lymphatic system
Immune corridor
Parallels blood system
Dumps into veins near heart
what is a meta organism?
dynamic microorganism environments sometimes centimetres apart
what are the 4 sources of acquiring microbiota?
Birth canal
Food
Breathing
environmental contact
what three microbes are naturally present in gut?
Lactobacilli
Coliforms
Anaerobes
