ALHT106 Lecture Notes - Lecture 8: Respiratory Tract, Kupffer Cell, Natural Killer Cell
Non-specific (innate) body defences:
-Non-specific defences = innate, or inborn defences; present from birth
-Prevent the approach, deny entry to the body, or limit the spread of pathogens and other
environmental hazards
-First line defences: physical barriers (e.g. intact skin, hair on head and in nostrils, mucociliary
escalator), and secretions (e.g. lysozyme, HCl, mucus)
-Second line defences: phagocytic cells, NK cells, interferons, complement, inflammation and
fever
-Innate/inborn/non-specific body defences work together with adaptive/acquired/specific body
defences to protect against infection and disease
-Non-specific defences do not distinguish one threat from another: the same response occurs
each time, no matter the pathogen/antigen
Innate/non-specific defences:
Physical barriers and secretions:!
Aim is to prevent approach of microorganisms or harmful environmental hazards
-hair on head may prevent a mosquito from biting you
-hair in nostrils or mucociliary escalator may trap inhaled pathogens
-intact skin prevents microorganisms from entering body
-secretions onto cutaneous or mucous membranes e.g. lysozyme in tears, dermacidin in sweat
onto the skin, mucus and cilia, and stomach acid
Phagocytes:
-Two types: microphages (neutrophils and eosinophils) and macrophages
-White blood cells/leukocytes which circulate in blood; move out of blood into infected or
damaged tissues
-neutrophils most common, and move through tissues to engulf cell debris and bacteria
-Eosinophils last common; target foreign compounds, allergens and pathogens coated with
antibodies
-Macrophages are large; many types; derived from monocytes (WBC); some stay in tissues e.g.
microglia, Kupffer cells and alveolar/phagocytic dust cells
Immunological surveillance/ NK cells:
-Natural killer (NK) cells constantly monitor body tissues (known as immunological surveillance);
move through the ISF
-Detects “abnormal” antigens so responds to and kills and cell with an abnormal antigen
-NK cells kill bacteria in ISF, cells infected with viruses, abnormal body cells and cancer cells
-Respond immediately upon contact with abnormal/foreign cell
-NK cell membranes contain the protein protectin, which protests them against the perforin they
release to lyse the abnormal/foreign cell
Interferons:
-Small proteins released to cause neighbouring cells to increase antiviral protein production, to
slow viral replication if a virus enters a cell
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