1. Infection and immunity overview Flashcards
What are the types of microorganisms / infectious agents?
Unicellular:
- viruses
- bacteria
- Fungi
- Yeast
- Protozoa
Multicellular:
- Helminths (worms)
Agents:
- Prions
Define pathogens
Pathogens - microorganisms / infections agents that cause disease
What are the ‘big-three killers’ infectious diseases?
‘Big-three killers’ infectious diseases:
- Malaria
- HIV/AIDS
- TB
What is a communicable / non-communicable disease?
Communicable - infectious
Non-communicable - non-infectious
What is the sign that healthcare has been improving in preventing communicable diseases?
The # of deaths from communicable diseases has decreased recently - healthcare is improving - neonatal communicable conditions show largest decrease
How has the COVID-19 pandemic influenced deaths from the ‘big-three’ infectious diseases?
COVID-19 has impaired management of the ‘big-three’ infectious diseases:
- co-infections: in combination with COVID-19 - more deaths
- resources: more allocated to fight COVID-19 - less for ‘big-three’ - more deaths
What wider impacts do infectious diseases have?
Cause widespread societal and economic impacts on quality of life:
- lost working days
- disability
- food industry
- physical and psychological suffering
What are the types of pathogens by their inhabiting environments?
- Environmental: water, soil
- Live in hosts: humans, animals, insects, plants
What are the types of pathogen transmission?
- Physical contact
- Ingestion
- Inhalation
- Via vectors (ex mosquitoes)
How are pathogens adapted to exploit the host’s functions of life?
Pathogens exploit host’s functions of life sites for transmission - have adapted to break barriers - major diseases (ex pneumonia, COVID-19, TB)
Are all microorganisms pathogenic?
No, human micriobiome - symbiotic relationship
What are the beneficial functions of microbiome?
- digestion
- protection against pathogens
- synthesis of nutrients and vitamins
What types of processes make pathogens harmful?
- Microbe-specific caused problems to the organism
- Host-specific caused problems - because of immune response (ex inflammation)
Why high pathogenicity is not a good pathogen survival strategy?
High pathogenicity would kill the host - pathogens need to replicate + transmit -> better to be mid pathogenic to exploit
What are the broad categories of pathogen adaptations for a successful infection?
- Site specific: ability of a pathogen to colonize and infect a particular tissue or organ within a host - ex: HIV targets immune cells that express CD4 receptors and chemokine receptor CCR5
- Host specific: ability of a pathogen to adapt to and exploit the unique characteristics of a particular host species - ex: production of toxins or virulence factors that target specific host tissues or organs - Vibrio cholerae produces cholera toxin that targets the intestinal epithelial cells of humans
What are the types host-specific adaptations of pathogens?
- Intra-host: ignored by immune system at one anatomical site but reacted at another
- Inter-host: can cross species barrier - disease in one host but not another (zoonotic infections)
What is zoonosis and reverse zoonosis?
Zoonosis - inter-species transmited infection spread from animal to human
Reverse zoonosis - inter-species transmited infection spread from human to animal
75% of newly emerging infections are zoonosis - jump species barrier - humans and animals share common ecosystem
Why does Ebola not cause disease in bats?
Inter-host adpatation - Ebola causes disease in humans but not bats because:
- constitutive interferon activity fights infection (innate immunity) (Interferons - group of signaling proteins - critical role in innate immune response - act by inducing an antiviral state in neighboring cells to prevent viral replication and spread)
- very large naive antibody sets which limit viral replication (adaptive immunity)
How can pathogens be inter-host adapted?
- Pathogen adaptation itself: result of selective pressures + transmission opportunities - determine viral evolution - genetic mutations/host switching/environmental changes
- Pathogen adaptation to specific host: more adapted to the immune response - changes in receptor binding/immune evasion strategies/replication and transmission strategies/host range and tropism
What are the good and bad roles of the immune system?
Good:
- controlling infections
- killing tumours
Bad:
- Immune pathology (autoimmune diseases, allergies)
- Graft rejection
- Metabolic diseases, mental health (?)
What organ environments use what barriers of defence mechanisms to prevent infections?
How can pathogens break the skin barrier?
- wounds / burns
- insect bites
- animal bites
- parasites burrow through skin
What are the types of immunity? Main characteristics
- Innate immunity: rapid, not specific
- Adaptive immunity: slower, very specific, memory
How does the infection rate change depending on absence of innate or adaptive immunity?
What are the killing mechanisms of innate immunity?
Mechanisms act rapidly + non-specifically to provide immediate protection against a wide range of pathogens:
- Phagocytosis
- Complement system (complement proteins cause pathogen cells to lyse)
- NK cells (cytotoxic granules - when released also harms the tissue
- Antimicrobial peptides
What are the types of T cells? What are their functions?
- Helper T cells (Th cells)
- Regulatory T cells (Treg cells)
- Cytotoxic T cells (CTL)
What is immune memory?
Explain how innate and adaptive immunities cooperate
What are cytokines? What are their properties?
Cytokines - chemical messengers in immune system communication
Explain how cell to cell contact helps communication in the immune system
Why do lymph nodes increase upon infection?
Because lymph nodes are the focal points to immune cell communication + initiate adaptive immunity response
Explain the full sequence of events of the immune system fighting an infection
