Host Infection Flashcards
What are innate immune responses to infection?
Non-specific, does not result in immunological memory, no priming
Mucosa contains both innate and adaptive cells at site of infection
Activated by PAMPs and DAMPs
All cells bear some capacity to mount an innate immune response (Cytokine production, Inflammation, Cell surveillance)
What are physical/mechanical barriers to infection?
Anatomical - physical barrier, skin
pH - inhibits growth
Flushing and peristalsis - physically removes, tears, saliva, mucous (also a physical barrier)
Host microbiota - competitively inhibits growth
What are the major components of the innate immune system?
Antimicrobial peptides
Complement, phagocytosis
Pattern recognition receptors - cell membrane markers etc.
NK cell activity
Plasmacytoid DCs - subset of dendritic cells produce antimicrobial cytokines instead of presenting antigens.
Polymorphonuclear leukocytes (PMNs) - granulocytes, component of white blood cells. Neutrophils, eosinophils, basophils etc.
What are the major features of the adaptive immune response?
Specific, involves complex developmental processes, involves priming of naive cells, results in immunological memory
Professional antigen presenting cells (APCs) sample the periphery and migrate through lymph
Activated by antigen presentation on MHC
B cells (mainly produce antibodies) T cells (remove and regulate with cytokines)
Takes longer than innate (hours to days vs. days to weeks)
What are involved in the adaptive immune system?
Specialized APCs in specialized sites
Major processes during an adaptive immune response (Antibody production, Cell cytotoxicity, memory generation)
Major components of the innate immune system (APCs, T cells, B cells)
What is common about complement and antibody activation?
Opsonization of antigens/pathogens leading to phagocytosis and pathogen destruction
NK cells are activated by both (changes in surgace MHC expression etc)
NK cells activate multiple components of both (IFN gamma production, inflammatory cytokine production etc)
Dendritic cells have both innate and adaptive immune functions
What are characteristics of passive immunity?
Transfer of active immune mediators to a host
typically antibodies
maternal transfer - milk (Pathogens can also be transferred e.g. HIV)
artificial transfer - antitoxins, antiserum, antivenom
provides protection against antigen
does not provide memory - antibody half life is days to weeks, it is transient
What are characteristics of active immunity?
The production of active immune mediators within a host
Innate and adaptive (humoral and cellular)
Provides protection against antigen
Provides immune memory
What are the general patterns of innate antibacterial immunity?
Innate: PAMPs active TLRs adn NLRs leading to activation of NFkB transcription factor, inflammation, antigen presentation (cell wall components, flagellin, modified DNA)
Bacteria activate antimicrobial peptides leading to bacterial cell wall destruction
Bacteria activate the complement cascade leading to phagocytosis
What are general patterns of adaptive antibacterial immunity?
Processing of extracellular antigens leads to activation of a largely humoral response (antibody mediated)
Th17 cells and antibodies promote clearance of extracellular bacteria
Th1 cells promote clearance of intracellular bacteria
What are factors that adaptive immunological memory and sterilizing immunity depends on?
Pathogen specific factors (breadth and duration of antigen presenation, pathogen evasion mechanisms, host immune competency)
What are patterns of antibacterial immunity in bacteremia?
Blood glucose levels generally decrease - bacteria is using it
blood protein levels relatively normal - Bacteria also producing protein?
Neutrophilia may be an indicator of bacterial infection
What are patterns of antibacterial immunity in CNS infection (meningitis/encephalitis etc)
CSF glucose levels generally decrease
CSF protein levels relatively normal
Neutrophilia may be an indicator of bacterial infection
What are patterns of antibacterial immunity in bacteria who evade phagocytosis?
Granuloma formation leads to immune mediated damage - centre becomes necrotic
Ie mycobacterial disease (TB, leprosy)
Also a feature of some fungal infections
What are the general patterns of innate antiviral immunity?
PAMPs activate TLRs, NLRs, and RLRs leading to activation of NFkB transcription factor, inflammation, antigen presentation (dsRNA, Non-self RNA)
Many viruses alter MHC expression, leading to recognition and destruction by NK cells
Type 1 IFNs are responsible for the induction of an antiviral state in affected cells (inhibition of viral gene expression, apoptosis of infected cells, promotion of antigen presentation etc)
