third colloq Flashcards
Five stages of infectious disease
- incubation stage
- prodromal stage
- invasive stage
- decline stage
- convalescence stage
Types of infection according to…
- origin (endogenous, exogenous)
- spread (localized, systemic)
- Symptoms
- Duration
- quantity of species
Transmission routes of infections
- contact
- fecal-oral
- alimentary
- aerogenic
- transplacental
- via vectors
Occurrence of infections in society
- sporadic (isolated)
- endemic (regular and continuing with no time Limit)
- epidemic (increased within localities and time periods)
- pandemic (increased with no limitations)
lethal doses
Dosis lethalis minima
Dosis lethalis certa
letalis dosis 50
bacterial toxins
Exotoxins: actively secreted
Endotoxins: part of outer membrane, not released unti bacterium is killed; can cause Inflammation
toxinosis: pathogenesis caused by the bacterial Toxin alone
types of acquired immunity
natural active immunity (after infection)
natural passive immunity (antibodies from mother to Infant)
artificial active immunity (vaccines)
artificial passive immunity (immune Serums)
Types of innate immunity
1- constituitive: barriers, Body temp.)
2- Recruitment: complements, chemokines
3- Pathogen triggered (neutrophils, macrophages, NK)
Secondary lymphoid Organs and their functions
LYMPH NODE
- filters fluid
- where Antigen presentation occurs
SPLEEN
- filters fluid
- Antigen presentation
- removes old RBCs and platelets
- filters Antigens, Bacteria, viruses
MALT
- filters fluid
- Antigen presentation
Nonspecific defense vs specific defense
NONSPECIFIC
- mechanical barriers
- chemical/ humoral factors
- cellular facotrs
- pathophysiological processes (Inflammation, Fever…)
SPECIFIC
- cellular (T and B cells)
- humoral (antibodies)
Humoral factors of innate immunity (9)
- defensins –> kill pathogens
- lysozymes –> hydrolysis of peptidoglycan
- ß-Lysin –> Lysis of bact. cell
- lactoferrin –> competes for iron
- lactoperoxidase –> bactericidal activity
- Properdin –> activates complement
- Interferons –> cell killing
- Mannose-binding proteins –> activate complement
- Complement –> phagocytosis, Lysis, inflammation
Cellls of the innate immunity
- neutrophils: phagocytose and kill
- eosinophils: against parasites and in allergies
- basophils: in allergic Response, release histamine…
- Monocytes: MHC II and phagocytose in blood
- Macrophages: same only in tissues
- Dendritic cells: MHC I and II in tissues and lymph nodes
- NK cells: kill Virus infected or Tumor cells
Process of inflammation
- Activation of dendritic cells, macrophages, NK cells
- Vasodilation
- Increased vascular permeability –> neutrophils into tissue
- Exudation of fluid, proteins, RBCs and WBCs into tissue
- Vascular stasis to allow chemical Mediators and infalmmatory cells to collect and response
Process of Fever
- increased Body temp. by pyrogenes –> effect on Hypothalamus
- exogenous pyrogens stimulate release of endogenous pyrogens from macrophages
- Fever lowers the Plasma iron Levels
- pagocytosis, incr. Interferons, breakdown of lysosomes
Process of Acute Phase response
–> increased production of specific blood proteins called acute Phase proteins (CRP, MBP)
- inititate complement
- initiate or accelerate Inflammation
- stimulate Chemotaxis of the phagocytic cells
Helper T cells and their functions
TH1: early and local –> increased inflamm. Responses
TH2: late and systemic –> decreased inflamm. Responses
TH17: Epithelium and neutrophils
CD8 T cells and their functions
CTLs:
- eliminating infected cells
Suppressor T cells:
- antigen-specific Regulation of helper T function
Characteristics of antigen
T DEPENDENT ANTIGEN –> must be presented to T and B cells for Ab production
T INDEPENDENT AG –> with large, repetitive structures, can directly activate B cells resulting in production of IgM
- contain Epitopes –> are the actual structures that interact with single antibody molecule
- TCR can only recognize linear Epitopes conformational epitopes
Bacterial antigens
- bacterial structure components somatic (O) Antigen capsular (K) Antigen Flagellar (H) Antigen - bacterial exoenzymes - bacterial exytoxins - bacterial superantigens
IgD
- on Surface of B cells together with IgM
- activates B cell growth
IgM
- on Surface of B cells with IgD
- activates complement pathway
- pahgocytosis and bacteriolysis
- monomeric igM vs pentameric IgM connected with J chain
IgG
- crosses the placenta
- important in the anamnestic repsonse
- Chemotaxis, faciliates phagocytosis, fixes complement
- four subclasses
IgA
- as momomer, dimer, trimer, multimers with J chain
- Serum IgA and secretory IgA
- secretory IgA for localized immunity
IgE
- receptor for Allergens and parasite Antigens
- when enough UgE is on mast cells, they release histamine, prostaglandin, platelet activating factor, cytokines
- in type I hypersensitivity reactions!
Activation of T cell responses
- First Signal: Antigen specific, MHC-TCR
2- Second Signal: enhances previous Signal
3- Third Signal: for production of Interleukins –> T cell is activated
Mechanisms of the antibacterial immunity responses
1- Infection 2- Innate Responses --> neutrophils --> monocytes, macrophages --> acute Phase respones 3- Antigen-specific --> early (B-cells, Interleukins, Interferons) --> later (B-cells, Memory cells)
Mechanisms of the antivrial immunity responses
1- infection 2- innate Responses --> NK cells --> dendritic cells 3- Antigen specific --> early (B-cell) --> leater (B cell, Memory cell)
Activation of B cell responses
Th1 and Th2 make B cells develop intp Plasma cells which produce antibodies
Table of hypersensitivity reactions
look in summary
Type I hypersensitivity
1- exposure to Antigen 2- activation of Th2 cells 3- production of IgE antibodies 4- binding to mast cells --> sensitisation 5- re-exposure to Antigen 6- release of mediators
Mechanism of desensitization
- denatured allergen under Skin
- T-reg –> no production of IgE
3- Th1 for IgG –> IgG secreted
4- IgG Abs intercept antigen
Type II hypersensitivity reaction
IgG and IgM
leads to cell Lysis, tissue Damage, loos of functions, Agglutination of blood cells
- complement activation via classical pathway
- antibody dependenet cell-meidated cytotoxicity
- anti-receptor activity
Type III reaction
1- Ag-Ab complex is formed
2- IC is deposited in tissue –> activating complement
3- This attracts neutrophils –> release lysosomal Enzymes –> inflammation
type IV reaction
- delayed, cell-mediated
- Th1 recognize Antigen Bound to APCs
2- release of cytokines –> mediating immune Response
3- CTLs_ destroy target cells on contact
- -> overreaction of helper T and overprocution of cytokines
- -> Damage of tissues, Inflammation, cell death
Types of vaccines
- live vaccines: waekened from of pathogen
- subunit: made from other small peices taken from pathogen
- inactivated /Killed: not as strong, we Need more than one shot
- DNA vaccines: contain DNA that codes for specific Antigens from a pathogen
Comparison of live and inactivated vaccines
LIVE VACCINES
- low doses and single shot
- Long term
- IgG, IgA
- good cell mediated Response
- labile in tropics
- occasional interference, mild Symptoms, Reversion to virulence
INACTIVATED VACCINES
- high dose, multiple shots
- short term
- IgG
- poor cell mediated Response
- no heat lability in tropics
- no interference, no Reversion
- occasional sore arm
Immunological assays
- Tests that measure the presence of concentration of a molecule through the use of an antibody
- molecule detected –> analyte
Agglutination reactions
–> based on Formation of bridges btw. bivalent (IgG) or multivalent (IgM) antibides and antigenic particles with multiple Epitopes
DIRECT
- Antigen on RBCs bind to antibodies
INDIRECT
- Antigen is absorbed on Surface (Latex, colloid Gold)
- Antigens bind with antibodies
Toxin-Antitoxin reaction
- Neutralization reactions can detect bacterial toxins and antibodies to certain viruses
- in botulism: animals are infected with pathogen; then they are given Variety of Antitoxins
- if animal survives, then Antitoxin was successful
Percipitation reaction
IN FLUID
- Ab in Bottom
- soluble Ag added
- Zone of equivalence –> precipitin ring
IMMUNODIFFUSION
- Ab and Ag both in agar gel
- diffuse towards another and precipitin bands form
IMMUNOELETROPHORESIS
- Ag in agar gel with Electric current –> spread
- through of antobody in middle
- curved precipitin bands form
RADIAL IMMUNIDIFFUSION
- gen containing antobody
- wells with Antigens
- precipitin rings form
- Diameter of the ring is proportional to the logarithm of the Ag concentration
Complement Fixation test
–> to detect the presnece of either specific antibody or speific Antigen in a patients Serum
Serum (either with antibody or not)
1- Add Antigens
2- Add free complement
3- Add red blood cells with attached antibodies
—> RBCs are either lysed by free complements or not
Immunofluorescence assay
DIRECT
- to target unique Antigens present in the Bacteria but not present in mammals
- cell Surface has Antigens and antibody with fluorescnent dye binds to ot
INDIRECT
- secondary antobidy with dye binds to Primary antibody –> are for example Cancer markers
- used to Diagnose autoimmune blistering diseases –> detects autoantibodies
ELISA (Enzyme linked immunosorbent Assay)
AB DETECTION
- Ag + Serum
+ antiimmunoglobulin Enzyme
+ Substrate
AG DETECTION
- Ab + specimen
- second antiviral antobody
- antiimmunoglobulin Enzyme
- substrae
Immunoblotting method
- -> to detect posttranslational modifications (HIV, proteins in Tumors)
- -> using antibody-based probes to obtain Information about target proteins
- mix of proteins is separated with the help of gel-electrophoresis (charge, size, …)
- bands become visible
PCR
- -> to make several copies of a specific DNA Segment by DNA polymerase
- -> for testing genetic carriers, identification of microorganisms
- denaturation –> heating, cleaving
2- annealing –> cooling, primers bind
3- Extension –> DNA polymerase makes copies
TYPES
- hot start PCR
- fast PCR
- real time PCR
- nested PCR
MALDI-TOF Mass spectomentry
- sample is mixed in large quantity of Matrix
- Matrix absorbs UV light and converts it to heat Energy
- small part og Matrix is vaporized together with sample
- charged Ions of various sizes are on sample slide
- lighter Ions move faster through the drift space until they reach the detector
- -> for identification of Bacteriaof all Kinds, fungi, mycobatera
- -> for antimicrobial susceptibility test
