Infectioin 2 Innate Immunity Flashcards
What groups of people are naturally immunosuppressed?
Pregnant people
Below 5
Over 65
Immune system definition
Cells and organs that contribute to immune defences against infectious and non infectious conditions (self and non self)
Infectious disease meaning
When the pathogen succeeds in evading and/or overwhelming the host’s immune defences
Roles of immune system
- pathogen recognition
- containing and eliminating infection
- self regulation: minimises damage to host
- remembering pathogens: prevents disease from reoccurring
Types of immunity
Innate immunity
Adaptive immunity
Describe innate immunity
Immediate protection
- Fast
- Lacks specificity - generalised
- Lacks memory
- No change in intensity
Describe Adaptive immunity
Long lasting protection
- Slow
- Specific
- Immunological memory
- Changes in intensity
What are the types first lines of defence?
Physical barriers
Physiological barriers
Chemical barriers
Biological barriers
What are physical barriers to infection?
Skin
Mucous membranes
Bronchial cilia
Where are mucous membranes to infection?
Mouth
Respiratory tract
GI tract
Urinary tract
What are physiological barriers to infection?
Diarrhoea
Vomiting
Cough reflex
Sneeze reflex
What are chemical barriers to infection?
Antimicrobial molecules
Low pH
Where in the body has low pH?
Skin 5.5
Stomach 1-3
Vagina 4.4
Examples of antimicrobial molecules
- IgA - tears, saliva, mucous membrane
- lysozyme - sebum, urine, perspiration
- mucus - mucous membranes
- beta defensnins - epithelium
- gastric acid and pepsin
What are biological barriers?
Commensals microbes/normal flora
Compete for space
Locations of normal flora
Nasopharynx
Mouth
Throat
Skin
GI tract
Vagina
Absent in internal organs
Benefits of normal flora
- compete with pathogens for attachment sits and resources
- produce antimicrobial chemicals
- synthesis vitamin - K, B12, other B vitamins
- immune maturation
Normal flora on skin
Staphylococcus aureus
Staphylococcus epidermidis
Streptococcus pyogenes
Candida albicans
Normal flora on mouth and nasopharynx
Streptococcus mutans
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus species
Normal flora in GI tract
Escherichia coli
How can normal flora be displaced from its normal location?
- Breaching skin integrity
- Fecal-oral infection - foodbourne
- Fecal-perineal-urethral route»_space; UTI
- Poor dental hygiene/dental work»_space; infective endocarditis
Ways skin integrity can be breached
Skin loss (burns)
Surgery
IV lines
Skin diseases
Injection drug uses
Tattooing
Piercing
When do clinical problems start with normal flora?
- displaced from normal location
- overgrowth and becomes pathogenic when host is immuno compromised
- depletion due to antibiotic therapy
What does depletion of Candida albicans due to antibiotics cause and where?
Vaginal thrush
What does depletion of clostridium difficile cause and where?
Intestines
Severe colitis + dehydration
Main phagocytes
Macrophages
Monocytes
Neutrophils
Key cells in innate immunity
Main phagocytes
Basophils/mast cells
Eosinophils
Natural killer cells
Dendritic cells
Macrophages function
- Phagocytosis
- Produced cytokines/chemokines > recruit neutrophils
- Present microbial antigens to T cells
Monocyte function
Recruited at infection site and differentiate into macrophages
Neutrophil function
Recruited by chemokines (produced by macrophages) at site of infection
Ingest and destroy pyogenic bacteria
What are pyogenic bacteria?
Staphylococcus aureus
Streptococcus pyogenes
What produces chemokines and what do they recruit?
Produced by macrophages
Recruit neutrophils
What are basophils important in?
Allergic reactions
Inflammation
Eosinophils function
Defence against multi cellular parasites
Natural killer cell function
Kill all abnormal host cells
What does PAMP stand for?
What is it?
Pathogen associated molecular patterns
Antigenic marker on the surface of pathogens
What does PRR stand for?
What is it?
Pathogen recognition receptor
On phagocyte surface to bind to PAMP so they can recognise and destroy bacteria
Role of opsonins
Tag pathogen make them more visible to phagocytes
Examples of encapsulated bacteria
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae b
How are pathogens recognised by phagocytes?
PAMPS
PRR
Opsonin examples
- Complement protein: C3b, C4b
- Antibodies: IgG, IgM
- Acute phase proteins: CPR, MBL
What clinical problems start when phagocytosis is reduced?
Decreased spleen function
Decreased neutrophil number
Decreased neutrophil function
Antimicrobial actions
C3a and C5a
C3b
C5-C9
C3a and C5a function
Recruitment of phagocytes
C3b function
Opsonisation of pathogen
C5-C9 function
Killing of pathogens via membrane attack complex
What is an opsonin?
- Coating protein that bind to microbial surface
- Causes enhanced attachment of phagocytes + clearance of microbes
What are involved in the oxygen dependent killing mechanisms (respiratory burst)?
Hydrogen peroxide
Hydroxyl
Nitric oxide
What are involved in oxygen independent killing mechanisms?
Lysozymes
Lactoferrin + transferrin
Enzymes
How do complement proteins contribute to innate immunity?
Enhances the immune system by promoting opsonisation of pathogens > phagocytosis
Name some complement proteins and their function
- C3a + C5a - recruit phagocytes
- C3b - opsonisation
- C5-C9 - membrane attack complex > kills pathogens
Systemic actions of cytokines
Complement activation
Neutrophil mobilisation
Increased body temp»_space; fever
Local actions of cytokines
Vasodilation
Increased vascular permeability
Expression of adhesion molecules
Pathways in the complement system + what they are initiated by
- Classic pathway: initiated by antibody-antigen interactions
- Alternative pathway: initiated by cell surface microbial components e.g. endotoxins
- MBL pathway: MBL binds to mannose containing residues of proteins on microbes
What do phagocytes have to allow them to recognise and bind to microbes?
PRRs
What is the antigenic marker found on a microbe?
PAMP
Outline the process of phagocytosis
- chemotaxis + adherence of microbe to phagocyte
- phagocyte ingests microbe
- phagosome formed
- phagosome + lysosome > phagolysosome
- enzymes from lysosome digest microbe
- forms residual body
- discharge of waste materials
