Defending Against Infection

• Immune Surveillance - cells monitor the body for infection*These “surveillance cells” ID body

cells by their surface protein markers

Pathogens - disease carriers - have different protein markers

Pathogens are opposed by 3 lines of defense

3 lines of defense

1. Epithelial layers• Skin *secretes chemicals*surface is acidic*lysozyme attacks and digests

pathogens*host to symbiotic bacteria

3 lines of defense1.epithelial layers, con’t

• Mucus membranes of digestive system, nasal passages, lungs, reproductive tract

*mucus traps pathogens*cilia sweeps away

mucus(+pathogens)*smoking destroys ciliaIf first line is penetrated . . . . .

3 lines of defense2. Counterattacks• Killer cells: macrophages, neutrophils,

natural killer cells• Killer proteins: create holes in

pathogen’s cell membrane• Inflammatory response: a blockade

that isolates the damaged area• Temperature response: fever - inhibits

microbial growth

3 lines of defense3. Immune System involves 4 kinds of

white blood cells• killer T cells attack and kill infected cells• B cells label invaders for destruction• Helper T activate killer T +B cells• macrophages consume pathogens and

infected cells

Lymphatic and Immune System• Consists of cells, vessels,

structures, organs, and a fluid called lymph

•Circulates body fluids and defends against pathogens

Lymphatic and Immune System

• Interstitial fluid*fluid between cells and blood

vessels, draining waste*as this fluid moves into lymphatic

vessels its name changes to lymph

Lymphatic and Immune System

• Lymph *interstitial fluid that has moved into

the lymphatic vessels where it meets lymphocytes and travels through nodes

*you produce 3L of lymph per day

Lymphatic and Immune System

• Lymphocytes *white blood/immune cells• Vessels*where lymph travels, similar to

veins*from capillary size to aorta• Ducts very large vessels to drain

very metabolically active areas, ex. Brain

Lymphatic and Immune System

• 600 Nodes*little ‘bulbs’ that lymph passes

through*contain many lymphocytes to kill

pathogens and ‘eat up’ worn out cells

*swollen glands are nodes enlarged with lymphocytes and pathogens during an infection

Lymphatic and Immune Systemnodes con’t

• Tonsils are modified nodes of the throat, this position allows quick attack on inhaled or ingested pathogens

Lymphatic and Immune System

Additional parts of the immune system:• Red marrow produces precurser (baby)

blood cells• Spleen *largest mass of lymphatic cells in the

body*maturation, storage, and fighting of

pathogens in blood• Thymus site of T-cell maturation

Lymphatic and Immune System

• Antigens: foreign invaders that cause an immune system response

*you have millions of different B cells and million of different T cells to respond to all the millions of antigen types you will encounter

*antibodies respond to each antigen as a lock fits a specific key

Lymphatic and Immune System

Your immune system must recognize the rest of your body cells as belonging to you and must be able to distinguish between dangerous invaders and non-dangerous invaders

*dysfunction leads to . . . .

Lymphatic and Immune Systemdysfunction

• Allergies: the immune system over-reacts to non-dangerous invaders

*varies in severity from bothersome to deadly

• Autoimmune diseases: immune system sees your own cells as dangerous invaders and destroys them

*Ex. Rheumatoid arthritis, lupus

Attack on theLymphatic and Immune System

• HIV virus attacks and destroys the immune system resulting in AIDS

• AIDS is a collection of diseases that your immune system, if still intact, would have fought off

treasure your immune system