Phase 1 - Week 2 (Immunology, Bacteria/Viruses) Flashcards
Describe the production of T lymphocytes
- Mature in the Thymus - repertoire of T cells required for life, selection/deletion of autoreactive cells preventing autoimmunity
- Leave Thymus as either CD4 (helper) or CD8 (killer) cells and travel to lymph nodes/spleed to be clonally selected when TCR detects specific antigen.
List the innate WBCs
- Interferons
- Neutrophils
- Macrophages
- Eosinophils
- Basophils
- Natural Killer Cells
Why are bacterial infections harmful/difficult to treat?
Bacteria have short lifespans and produce large numbers of offspring so can quickly adapt to changing conditions. They can evolve to adapt to new hosts or become resistant to treatments and medicines such as antibiotics.
Explain how microbiological barriers contribute to the 1st line defences of the Innate immune system
Normal flora of the gut/skin prevent pathogens from dividing
Guided therapy
- Identify cause of infection and select agent based on sensitivity testing
- Used for mild infections that do not need to be immediately treated/to rationalise therapy in patients already on therapy
- Narrow spectrum - achieve clinical cure with little impact on colonisation + resistance
How is viral messenger RNA synthesised in DNA viruses?
mRNA is formed using the host’s RNA polymerase to transcribe directly from the viral DNA
Describe the methods by which viral particles can be released following assembly
- Budding through cell membrane - will acquire envelope
- Released following cell death
- Released following cell lysis
Explain how chemical barriers contribute to the 1st line defences of the Innate immune system
- Acid secretions in the stomach
- Lysozyme enzyme in tears/saliva
- Low pH of skin due to sweat secreted by eccrine glands
List the classifications of methods by which antibiotics can be used
- Guided therapy
- Empirical therapy
- Prophylactic therapy
Describe the main functional divisions of the immune system
- Innate immune system
- Adaptive immune system
Describe the outer envelope of a virus
Lipid bilayer or host cell origin, into which virus proteins and glycoproteins are inserted
Bactericidal antibiotics
Acheive sterilisation of the infected site by directly killing bacteria. Lysis of bacteria can lead to release of toxins and inflammatory material.
Describe the features of the adaptive immune system
- T lymphocytes: Cytotoxic T cells and Helper T cells
- B lymphocytes
Bacteriostatic antibiotics
Suppress growth but does not directly sterilise infected site. Requires additional factors to clear bacteria - immune mediated killing.
Describe genetic information in bacteria
- long double-stranded circular molecules of DNA
- either tightly coiled into a region called the nucleoid or extrachromosomal, present as small, circular, self regulating DNA molecules called plasmids
Describe the features of the Innate immune system
1st line defences - physical, chemical + microbiological barriers
2nd line defences - phagocytes, natural killer cells + the complement system
List the possible bacterial cell surface structures/appendages
Capsules, flagella + pilli
What is the basic function of Helper T cells?
Help B cells become activated
Explain the mechanism of action of Cytotoxic (CD8) T cells
- Recognise antigens on infected cells
- Induce death of cells - bind, induce cell death (apoptosis) by punching holes in cell membrane using perforin
- Prevent pathogen (e.g. virus) from spreading - sacrifice infected cells
Flagella
Long helical filaments extending from the cell surface which enable bacteria to move in their environment
How to bacteria obtain nutrients?
Mainly by taking up small molecules across the cell wall
Describe the types of nucleic acid found in viruses
Linear or circular RNA or DNA
Prophylactic therapy
- Preventing therapy before it begins
- Healthy people exposed to surgery/injury/infected material
- Immunocompromised - HIV, transplantation, splenectomy
How are bacteria classified?
Through Gram staining - as Gram positive or Gram negative
Complement System
- Involves a cascade of enzymes
- 3 functions - recruitment of inflammatory cells, opsonisation of pathogens, killing of pathogens
Describe antibiotic resistance mechanisms
- Mutation of target site
- Inactivating enzymes
- Limit access - reduced permeability, increased efflux
Genes mediating resistance can often by easily trasnsferred
Compare the Innate and Adaptive immune response
Innate:
- No memory
- Immediate standard response
- Recognises pathogen specific molecular patterns
Adaptive:
- Memory
- Heightened response on second exposure
- Clonal expansion
- Unique antigen receptor on each lymphocyte
Describe the structure of bacterial cell walls and how this allows for Gram staining
The main structural component of the cell wall is peptidoglycan, it can form a thick external layer (Gram positive) or a thin internal layer (Gram negative)
Peptidoglycan
Mixed polymer of hexose sugars and amino acids
Neutrophils
- Abundant in blood
- Phagocytise pathogens in acute inflammation
- Contain lysosomes to digest the microbe
- Release soluble mediators
- Short lived
- Contain bacteriostatic and toxic factors
What is the basic function of cytotoxic T cells?
Kill infected cells by apoptosis
Dendritic cells
Antigen-presenting cells which have MHC class II proteins. They mature from monocytes in the blood.
Describe the phagocytes involved with the 2nd line defences of the Innate immune response
Monocytes which mature into macrophages/neutrophils