Immunology and Pathology Flashcards
What are extremophiles?
Microorganisms adapted to live in harsh and extreme environments
What are thermophiles?
Bacteria with optimum growth temp >45
What are psychrophiles?
Bacteria with optimum growth temp below 20
What are bacteria that withstand high osmotic pressure environments called?
Halophiles - high salt environments and spoilage of salted foods
What are bacteria that live in acidic and alkaline environments called?
Acidophiles
Basophiles
What are the 7 beneficial activities of microorganisms?
- Environmental cycles: C, N, O, S
- Agriculture and horticulture
- Food and drink: brewing, wine-making, baking, cheese
- Medicine: insulin, antibiotics
- Energy production: ethanol, methane, H2
- Solvent production: acetone, butanol
- Nutritional benefits and protective in man and animal
What are the 7 mechanical antimicrobial factors which microbiota must contend with in healthy host?
- Flushing action of liquids: saliva, urine
- Peristalsis of gut
- Skin: impermeable barrier
- Cough/sneeze reflex
- Mucus
- Cilia
- Shedding of epithelial cells
What are the 8 biochemical antimicrobial factors in health?
- Anaerobicity
- Acidity
- Sebaceous secretions
- Sweat: high salt
- Lysozyme: antibacterial enzyme
- Digestive enzymes
- Bile: detergent action
- Colonisation resistance
What are the 6 immunological antimicrobial factors in health?
- Complement
- Phagocytosis
- Inflammation
- Acute phase response
- Antibodies
- Cell-mediated responses
Why is infection control important?
Body surfaces are heavily colonised
Inanimate surfaces, instruments, H2O, air contaminated
Patients and staff may be carrying infections
Need to protect patients and staff from risk of infection
Dentists have responsibility for ensuring safety
What are some of the infection control procedures?
Hep B immunisation Sterile instruments/equipment Proper aseptic techniques Safe disposal of waste PPE General hygiene and cleanliness
What dental diseases are caused by microorganisms?
Dental plaque related disease: caries, periodontal disease
Other oral infections: abscess, mucosal infections, bone and sinus infections
Systemic disease: infective endocarditis, brain abscess
What are the 5 infectious agents in inc. complexity?
- Prions: infectious proteins
- Viruses: non-living, obligate intra-cellular parasites
- Bacteria: prokaryote
- Fungi: eukaryote
- Protozoa: eukaryote
What are prokaryotes?
Single-celled, contain RNA and DNA
Lack membrane bound nucleus
Single, circular DNA molecule as chromosome
Describe eukaryotes
Truly nucleated: uni/multicellular containing both RNA and DNA
Membrane bound nucleus and other organelles
What are prokaryotes and eukaryotes but viruses not?
Defined as living organisms
What are parasites?
Organism that lives in/on 2nd organism (host)
May have little/no harmful affect, in apparent or bring about damage/harm (pathogen)
What are commensals?
Microbes found colonising host that benefit or are essential to them
Describe bacteria
Unicellular
Reproduce asexually by binary fission
V small, v diverse (aerobes, anaerobes, microaerophilic, capnophilic)
Low generation time (mins)
What are the 2 important structural features of bacteria essential for their survival?
- Fimbriae: on surface; protect against phagocytosis, aid adherence to target
- Pilus: share genetic material; antibiotic resistance
What are the 6 main bacteria types that interact with man?
- Gram +ve
- Gram -ve
- Acid-fast
- Mycoplasma, ureaplasma
- Rickettsiae
- Chlamydia
Describe gram +ve bacteria
Thick peptidoglycan cell wall, possible protein layers, stain purple
Describe gram -ve bacteria
Thin peptidoglycan layer, 2nd membrane, periplasm (space), lipid rich, fragile, stain pink
What are acid-fast bacteria?
Bacteria with mycolic acids (waxy lipid) attached to peptidoglycan
Cross linking with arabinose and galactose
Does not stain by normal procedure
What is special about mycoplasma and ureaplasma?
Cytoplasmic contents surrounded by well developed PM thus resistance to antibiotics that target cell wall e.g. penicillins
How do viruses replicate?
Depend on host Adsorption Penetration Assembly Reslease
How do fungi reproduce?
Asexual - most freq. in good conditions
Sexual - fusion of gametes or gametangia
How do yeasts reproduce?
By budding
What is an important yeast in oral biology?
Candida albicans
When are the body surfaces sterile?
Immediately before birth, rapidly colonised after birth
What body surfaces are normally non-sterile?
Skin, mouth, upper respiratory tract, GIT, genitourinary tract
Acquire from environment and contact with other people
What body surfaces are usually sterile?
Blood, CSF, lymph, bones, joints, internal organs
What secretions are contaminated?
Faeces heavily
Saliva, tears, sebum sterile within glands, contaminated as soon as reach mucous membrane/skin
What 5 factors effect establishment of microorganisms?
- Exposure of site to potential organism
- Availability of suitable receptor sites
- Ability of organism to adhere to receptors
- Ability of organism to compete for nutrients
- Ability to evade/withstand host defence mechanisms
Compare resident and transient microflora
Resident: commensal organisms regularly present at different sites
Transient: colonise body for short periods of time, w/o causing disease
Define commensal
Organism that benefits from relationship with host but is neither directly benefits or harms host
Define opportunistic pathogen
Organism that only causes disease when host is immunocompromised or is transferred to unusual site
Define carriage
Person asymptomatically carries pathogen which can be transferred to others
Define colonisation resistance
Mechanism by which resident microflora act as barrier against colonisation by undesirable, exogenous organisms
Define pathogen
Microorganism that is capable of causing disease
Define virulence
Quantitative ability of a pathogen to cause disease - measure of degree of pathogenicity
Describe the possible consequences of resident microflora being absent
Poor physical development of gut Poor nutrient absorption in gut Vit. deficiencies Reduced host immune defences Susceptibility to colonisation by pathogens
Describe the consequences of resident microflora being suppressed
Overgrowth by antibiotic-resistant microorganisms
Colonisation by pathogens
What are the 4 possible mechanisms for colonisation resistance?
- Competition for receptor sites
- Competition for nutrients
- Creation of unfavourable micro-environments that discourage colonisation
- Production of inhibitory substances
Describe the advantageous metabolic activities of microflora of the vagina
Lactobacilli produce acid from glycogen, maintain low pH which is unsuitable for many exogenous bacteria
Describe advantageous activities of skin microflora
- Propionibacteria breakdown sebum, release FAs - inhibit some potential pathogens
- Some staphylococci produce peptide antibiotics which inhibit other bacteria
Describe advantageous activities of mouth and GIT microflora
Some bacteria produce bacteriocins which inhibit other organisms
What are 4 important gram +ve mouth microflora?
- Streptococci
- Actinomyces
- Bifidibacterium
- Lactobacillus
What are 4 important gram -ve oral bacteria?
- Aggregatibacter
- Porphyromonas
- Fusobacterium
- Prevotella
What 4 factors can disrupt normal flora at all sites?
- Suppression by antimicrobial agents allowing overgrowth of resistant organisms
- Changes in general health or immunological status
- Hormonal changes
- Local trauma
What 5 factors can disrupt normal flora of the mouth?
- Changes in diet
- Reduction in salivary production
- Dental disease
- Dental treatment
- Oral hygiene
What 3 factors can disrupt GIT flora?
- Changes in diet
- Functional disorders of gut
- Localised pathological lesion in gut
What 2 factors can disrupt female genital tract flora?
- Menstrual cycle, pregnancy
2. Infra-urine contraceptive device
What 2 factors can disrupt skin flora?
- Use of soaps, cosmetics, antiseptics
2. Wetness, dryness
What 2 factors can disrupt respiratory tract flora?
- Viral infections
2. Damage to ciliated epithelial cell function
What are viruses?
‘Non-living’, obligate intracellular parasites
What are the 4 distinguishable features of viruses?
- V small size
- Genome: DNA/RNA
- Metabolically inert: some have polymerases
- Replication: not true reproduction
Describe the structure of viruses
Capsid: protein coat made of capsomeres
Nucleic acid in capsid
Some have membrane derived from host cell
Receptor binding protein
On what 5 characteristics are viruses classified?
1. Virus particle morphology Type of nucleic acid: 2. DNA OR RNA 3. Intact or segmented 4. Single or double stranded 5. Linear or segmented
Differentiate between positive and negative RNA viruses
+ve: act directly as mRNA
-ve: transcribed by virus-associated RNA transcriptase to mirror-image +ve copy which then acts as mRNA
What 4 factors allow viral evolution to be so rapid?
- Genome duplication v quick
- No proof reading or error correction
- RNA viruses: nucleotide divergence 2%/yr
- Polymerases v high freq. of error
What are the 6 stages of the viral life cycle?
- Attachment
- Entry
- Uncoating
- Synthesis (of viral components)
- Assembly
- Release
Define episomal and proviral
Episomes: viral genomes free in cytoplasm or nucleus
Proviral: integrate into host genome
What is amantadine? How does it work?
Antiviral agent
1-aminoadamantane
Interferes with uncoating of virus
What is acyclovar and how does it work?
Antiviral
Inhibits viral reverse transcriptase
How do proteases inhibit viruses?
Prevent cutting up of viral proteins for assembly into capsid
How does ribavirin inhibit viruses?
Unknown
Ribonucleoside analogue
Prevents RNA synthesis and mRNA capping
What are the 5 leukocytes in order from most numerous to least?
- Neutrophils: 40-70%
- Lymphocytes: 20-45%
- Monocytes: 4-8%
- Eosinophils: 1-4%
- Basophils: <1%
What are the 2 types of leukocytes?
- Granulocytes
2. Agranulocytes
Which leukocytes are granulocytes and which are agranulocytes?
Granulocytes: neutrophils, eosinophils, basophils
Agranulocytes: lymphocytes, monocytes
Describe neutrophils
Multilobed nucleus: 2-6 interconnected lobes
Blue granules, pick up acid and base stains
Phagocytise and destroy bacteria
Describe eosinophils
Bilobed nucleus
Red/yellow granules
Role in ending allergic reactions and parasitic infections
Describe basophils
Bilobed nucleic hidden by large purple granules
Role in inflammation mediator
Granules secrete histamine
Describe lymphocytes
Round nuclei
Dense, purple staining, little cytoplasm
Immune response; act against specific antigens and infectious agents
Describe monocytes
Kidney shaped nuclei
Larges leukocyte
Transform into macrophages; phagocytic cells
What are the 2 types of lymphocytes?
- T cells: attack antigen directly
2. B cells: multiply to become antibody secreting plasma cells
What are the 3 basic functions of myeloid cells (WBCs)?
- Migration: move to site of infection
- Phagocytosis: engulf bacteria in vacuole
- Granule-release: different cells have different granules and purposes
What are the 4 functions of granule release from myeloid cells?
- Degradation of pathogens
- Chemotactic factors: cytokines that stim. release of more WBCs from bone marrow
- Activators of clotting and clot dissolution
- Factors that allow permeability
What is the overall affect of granule release?
Trigger and sustain inflammatory response
What is neutrophilia? When is it seen?
Inc. in number of neutrophils
- Infection
- Inflammation
- Tissue damage
- Myeloproliferative disorders
What 6 disorders can lead to eosinophilia?
- Allergic: asthma
- Skin: eczema, psoriasis
- Gut: ulcerative colitis
- Parasitic: Protozoa, metazoa
- Malignancies: Hodgkin’s disease, myeloproliferative
- Lung eosinophilia: tuberculosis
What conditions can lead to basophilia?
- Myeloproliferative: chronic leukaemia
- Occasionally chronic infections
- Severe hypothyroidism
In what situations does monocytosis arise?
- Recovery from acute infection
- Some chronic bacterial infection: tuberculosis
- Viral infections
- Collagen disease
- Monocytic leukaemia
In what 4 conditions can lymphocytosis arise?
- Viral infections: glandular fever
- Infections in children: whooping cough
- Other: TB, typhoid, toxoplasmosis
- Malignant lymphoproliferative disorders: lymphomas, lymphocytic leukaemias, myeloma
What are the 3 functions of lymphocytes?
- Helper cells: help B cells make antibodies
- Regulatory: regulate immune response
- Cytotoxic: kill virally infected cells
What is the role of natural killer cells?
Recognise and destroy cells infected w/ virus
Act against malignant cells
What are the 5 epithelial barriers in innate immunity?
- Mucus, peristalsis
- Enzymes
- Microbial
- Cells that recognise pathogen patterns, produce chemicals that disrupts viral replication
- Antibacterial peptides
What are the 5 molecules of the innate immune system?
- Lysozyme
- Pepsin-digestive enzyme
- Complement: plasma cells mark pathogens for phagocytosis
- Cytokines and Chemokines: cell-cell communication
- Antimicrobial substances: cryptidins, defensins
What are the 8 functions of antibodies?
- Neutralise toxins
- Neutralise viral activity
- Activating complement
- Agglutination
- Immobilisation of microorganisms
- Binding soluble antigen
- Antibody dependent cellular cytotoxicity: killing infected cells
- Opsonisation: marking bacteria
Describe the basic structure of antibodies
2 light chains and 2 heavy chains both w/ variable and constant region
Held together by S=S bond
Hinge region allows flexibility of antibody
What determines the isotype of antibody?
Position of S=S
Compare the constant and variable regions
Constant region is effector functions region where antibody can bind to receptor proteins
Variable region is the antigen binding portion and has 2 antigen binding sites. It is the upper part, V shape of Y.
How are polymers of antibodies held together?
J chains
Joining chains
Describe IgM, G, A
M: pentameric; 1st AB produced in immune response; best at activating complement
G: monomeric: AB associated w/ immune response in serum; best at opsonisation
A:
monomeric: in serum
dimeric: prevalent in secretions; signature Ig of all secretions
What are paraproteins?
Abnormal Igs synthesised by atypical cells in the reticuloendothelial system
If only light chains lead to Bence-Jones paraproteinaemia where proteins found in urine and blood
Most present themselves as m-component (monoclonal gammopathy) in electrophoresis
In what diseases is Bence-Jones paraprtoeinaemia found?
Myeloma
Malignant B cells only produce Ig light chains
What lymphoproliferative diseases are associated w/ paraproteins?
Myeloma, lymphoma, chronic lymphatic leukaemia
What Ig is the foetal Ig?
IgG
Only Ig that can cross placenta
What Ig is the maternal Ig?
IgA
Predominates in all secretions including breastmilk
What is hypogammaglobulinaemia?
Disorder caused by a red. in B cells thus there are less Ig resulting in immunodeficiency
What is X-linked Agammaglobulinaemia?
Total loss of Ig production
What can hypogammaglobulinaemia result in?
Recurrent infections
What is hypergammaglobulinaemia?
Overproduction of Ig resulting in inc. Ig levels in serum
Observed in chronic infections
What is Hyper IgM syndrome?
Inability to activate B cells fully prevents formation of germinal centres and switching of IgM to other isotypes
Why is AB class switching important?
As different isotypes have different functions
Describe the primary and secondary response
Primary: 1st contact w/ antigen, small Ig response, wanes after 3 weeks
Secondary: repeated contact, massive inc. in response, IgG production massively inc., IgM doesn’t inc.
