The Immune System

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Hemocytes also secrete antimicrobial peptides that disrupt the plasma membranes of bacteria.

Slide 8

Phagocytosis

Microbes

PHAGOCYTIC CELL

Vacuole

Lysosome

Containing

hydrolytic

enzymes

Slide 9

Innate Immunity Defenses of Vertebrates

The immune system of mammals is the best understood of the vertebrates.

Innate defenses include barrier defenses, phagocytosis, antimicrobial peptides.

Additional defenses are unique to vertebrates: the inflammatory response and natural killer cells.

Slide 10

Barrier Defenses

Barrier defenses include the skin and mucous membranes of the respiratory, urinary, and reproductive tracts.

Mucus traps and allows for the removal of microbes.

Many body fluids including saliva, mucus, and tears are hostile to microbes.

The low pH of skin and the digestive system prevents growth of microbes.

Slide 11

Cellular Innate Defenses

White blood cells = leukocytes engulf pathogens in the body via phagocytosis.

Groups of pathogens are recognized by TLR, Toll-like receptors.

Slide 12

TLR signaling

EXTRACELLULAR

FLUID

Lipopolysaccharide

Flagellin

TLR4

TLR5

Helper

protein

TLR9

TLR3

WHITE

BLOOD

CELL

VESICLE

CpG DNA

ds RNA

Inflammatory

responses

Slide 13

A white blood cell engulfs a microbe, then fuses with a lysosome to destroy the microbe.

There are different types of phagocytic cells:

Neutrophils engulf and destroy microbes.

Macrophages are part of the lymphatic system and are found throughout the body.

Eosinophils discharge destructive enzymes.

Dendritic cells stimulate development of acquired immunity.

Slide 14

Lymphatic System

Adenoid

Tonsil

Lymph

nodes

Spleen

Peyer’s patches

(small intestine)

Appendix

Lymphatic

vessels

Lymph

node

Masses of

defensive cells

Blood

capillary

Lymphatic

vessel

Tissue

cells

Interstitial fluid

Slide 15

Antimicrobial Peptides and Proteins

Peptides and proteins function in innate defense by attacking microbes directly or impeding their reproduction.

Interferon proteins provide innate defense against viruses and help activate macrophages.