Innate Immunity Flashcards
What are the four main features of the first line of defence?
Physical barriers
Physiological barriers
Chemical barriers
Biological barriers
What are physical barriers to pathogen entry?
Skin, mucous membranes- MALTs, bronchial cilia
What are some physiological barriers to pathogen entry?
Dn V
Coughing
Sneezing
What are some chemical barriers to pathogen entry
Low pH- skin stomach vagina
Antimicrobials
What antimicrobials are used in the first line of defence?
IgA- tears, saliva, MALTS Lysozyme- sebum, perspiration, urine Mucus Gastric acid and pepsin Beta defensins
What is the biological barrier to pathogen entry?
Normal flora- competes with pathogens for attachment sites and resources
These produce antimicrobial chemicals and synthesise vitamins K, B12
What kind of infections might poor dental hygiene cause?
Bactaraemia
Gingivitis
Who is most at risk from infection from poor dental hygiene?
Previous endocarditis
Damaged prosthetic valves
Asplenic and hyposplenic patients
How can normal flora be displaced from one area of the body to another?
Fecal oral
Breaching skin integrity- skin loss, injection drugs, surgery
Fecal perineal urethral route- UTI
Normal flora overgrows and becomes pathogenic when host is immunocompromised- malignancy, AIDS, diabetes, chemo
Or when normal flora is depleted by antibiotics- vaginal thrush
Intenstine- severe colitis
What are the three main components of the second line of defence?
Phagocytes
Inflammation
Chemicals
What are the different types of phagocyte?
Monocytes
Neutrophils
Macrophages
Which chemical do macrophages produce?
Cytokines/chemokines- these stimulate the movement of cells towards sites of inflammation and infection
What kind of receptors do phagocytes have?
Pathogen Recognition
Receptors- PRRs
What is an example of a PRR?
Toll Like Receptor
How are gram negative bacteria recognised?
Lipopolysaccharide PAMPs are recognised by TLR4 PRRs
What other cells are involved in the secondary line of defence?
Basophils/ mast cells
Eosinophils
Natural killer cells
Dendritic cells
What is involved in oxygen dependent killing?
Lysozyme
Lactoferrin/ transferrin
Cationic proteins
Proteolytic and hydrolytic enzymes
What is involved in oxygen dependent killing?
Respiratory burst- H2O2, hydroxyl radical, nitric oxide, superoxide
What are the effects of the cytokines released by macrophages?
Liver releases opsonins- CRP, MBL
Neutrophils mobilized from bone marrow
Inflammatory effects
Pyrogenic effects
What are some examples of opsonins?
Antibodies- IgG, IgM
Complement- C3b, C4b
Acute phase proteins- CRP, MBL
What are opsonins essential for?
Clearing encapsulated bacteria eg neisseria meningitidis, strep pneumoniae, haemophilus influenzae b
What do C3a to C5a do?
Recruit phagocytes
What do c5- c9 do?
Kill pathogens by forming membrane attack complex
What are the two ways that the complement system can be activated?
Alternative pathway- cell surface endotoxins eg e coli
MBL pathway-MBL binds to mannose containing residues of proteins found on many microbes
