Nonspecific Immunity
What is non specific immunity?• Protects regardless of pathogen• Includes first and second line of defense
– We’ll discuss third line in another lecture!
First line of defense
What is the first line of defense?
• Physical barriers• Chemical barriers• Normal Microbiota
What are physical barriers?
• Skin– Epidermis
• Many cells packed tightly
• Keratin• Arid• Benign microbes• sloughing
– Dermis
• Infections most likely from– Subcutaneous
staphylococci
What are chemical barriers?
• Lysozyme• Mucous
membranes• Lacrimal
apparatus• Saliva• Mucociliary
escalator• Epiglottis• Urine• Vaginal
secretions• Lactic acid
mantle
Normal Microbiota
• Microbial antagonism/competitive exclusion: Normal microbiota compete with pathogens.– Candida albicans– E.coli– Salmonella– Shigella
Second line of defense
What constitutes the second line of defense?
• Phagocytosis• Inflammation• Complement• Interferons
What are phagocytes?
• Literally means ___________
• All are leukocytes
• Neutrophils• Leukocytes• Monocytes
– Macrophages
• Eosinophils• Basophils
How do phagocytes work?
• Adherence • Phagosome• Phagolysosome
Does phagocytosis always work?
• Nope!• Adherence inhibition
– Streptococcus pyogenes M protein
– Capsules also• H pylori, Streptococcus
pneumoniae
• Ingested but still alive– Staphylococcus
leukocidins– Streptococcus
streptolysin
Staphylococcus
Does phagocytosis always work?
• Mycobacterium tuberculosis, HIV, Chlamydia, Plasmodium– Prevents fusion and acidification of
enzymes– Multiply within phagocyte
Chlamydia inclusion on pap smear cell
How do leukocytes get to a wound?
• Diapedesis• Chemotaxis
What about inflammation
?
• Pain• Redness• Swelling• Heat
• Acute inflammation– Boil: S. aureus
• Chronic inflammation– M. tuberculosis
What is fever?
• Pyrogens– Exogenous
• Some viruses, endotoxins
– Endogenous• Interleukin I
• Inhibits pathogens• Reduces iron availability• Stimulates immune response
The Complement System
• Serum proteins activated in a cascade.
Figure 16.9
Effects of Complement Activation
• Opsonization or immune adherence: Enhanced phagocytosis.
• Membrane attack complex: Cytolysis.
• Attract phagocytes.
Figure 16.10
Effects of Complement Activation
Figure 16.11
What happens with
complement?
– 20 subunits
– Cascade reaction
– Classic pathway• Binding to
mannan stimulates
– Animation
What happens with
complement?
– 20 subunits
– Cascade reaction
– Lectin pathway• Binding to
mannan stimulates
– Animation
What are interferons?• Antiviral
– Induce antiviral protein production– Causes neutrophils and macrophages to phagocytize bacteria.– animation
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