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