Nonspecific Immunity. What is non specific immunity? Protects regardless of pathogen Includes first and second line of defense –We’ll discuss third line.

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