Innate Immunity Flashcards
What is virulence?
Capacity of microbe to damage host
What is the definition of the immune system?
Cells and organs that contribute to immune defences against infectious and non-infection conditions
What is infectious disease?
When the pathogen succeeds in evading the host’s immune defences
What are the roles of the immune system?
Pathogen recognition
Containing the infection
Regulating itself
Remembering pathogens
What are some features of innate immunity?
Immediate protection Fast Lack of specificity Lack of memory No change in intensity
What physical barriers are involved in the innate immune system?
Skin
Mucous membranes (mouth, respiratory tract, GI tract, urinary tract)
Bronchial cilia
What physiological barriers are part of the innate immune system?
Diarrhoea, vomiting, coughing, sneezing
What chemical barriers are involved in the innate immune system?
Low pH of skin, stomach, vagina IgA (tears, saliva, mucous membrane) Lysozyme (sebum, perspiration, urine) Mucous Beta-defending (epithelium) Gastric acid and pepsin
What biological barriers are part of the innate immune system?
Normal flora in nasopharynx, mouth/throat, skin, GI tract, vagina
What are the benefits of having normal flora?
Compete with pathogens for attachment sites and resources
Produce antimicrobial chemicals
Synthesise vitamins (K, B12, other B vitamins)
What normal flora are found within the vagina?
Lactobacillus spp
What are some examples of normal flora that inhabit the skin?
Staphylococcus aureus Staphylococcus epidermidis Streptococcus pyogenes Candida albicans Clostridium perfringens
What are some examples of normal flora that inhabit the nasopharynx?
Streptococcus pneumoniae
Neisseria meningitidis
Haemophilus species
When do clinical problems involving normal flora occur?
When normal flora are displaced from its normal location to sterile location
Or when they overgrow
Or when they are depleted by antibiotics
Are macrophages present in all organs?
Yes
What are the functions of macrophages?
Phagocytosis, antigen presentation, production of cytokines
Where are monocytes present?
Blood
What is the function of monocytes?
They are recruited at infection site and differentiate into macrophages
Where are neutrophils present?
Blood (60% of blood leukocytes)
What are neutrophils recruited by?
Recruited by chemokines to site of infection
What is the function of neutrophils?
Ingest and destroy pyrogenic bacteria: Staphylococcus aureus and Streptococcus pyogenes
What is the function of basophils/mast cells?
Early actors of inflammation, important in allergic responses
What is the function of eosinophils?
Defence against multi-cellular parasites
What is the function of natural killer cells?
Kill all abnormal host cells (eg virus infected or cancer cells)
What is the function of dendritic cells?
Present antigens to T cells
What is opsonisation of microbes?
Coating proteins called opsonins that bind to the microbial surfaces leading to enhanced attachment of phagocytes and clearance of microbes
What are some examples of opsonins?
Complement proteins (C3b and C4b)
Antibodies (IgG, IgM)
Acute phase proteins (CRP, MBL)
What is the oxygen-dependent pathway of phagocytosis?
Toxic oxygen products produced to kill the pathogens - hydrogen peroxide, hydroxyl, nitric oxide etc
What is involved in the oxygen-independent pathway?
Lysozyme, lactoferrin/transferrin, cationic proteins (eg cathepsin), proteolytic and hydrolytic enzymes
How many serum proteins are in the complement pathway?
20
What is the alternative pathway of the complement system initiated by?
Cell surface microbial constituents (eg endotoxins on E. Coli)
What are C3a and C5a involved in?
Recruitment of phagocytes
What are C3b-C4b involved in?
Opsonisation of pathogens
What is C5-C9 involved in?
Killing of pathogens
Membrane Attack Complex
What is the MBL pathway of the complement system initiated by?
Initiated when MBL binds to mannose containing residues of proteins found on many microbes (eg Salmonella spp. , Candida albicans)
What could cause a decrease in neutrophil number?
Cancer chemotherapy, certain drugs (phenytoxin), leukaemia and lymphoma
What could cause a decrease in neutrophil function?
Chronic granulomatous disease (no respiratory burst)
Chediak-Higashi syndrome (no phagolysosome formation)
