1. Body Defenses and Immunity

2. Consists of two semi-independent parts
The Lymphatic System
Consists of two semi-independent parts
Lymphatic vessels
Lymphoid tissues and organs
Lymphatic system functions
Transports escaped fluids back to the blood
Plays essential roles in body defence and resistance to disease

3. Lymphatic Characteristics
Lymph - excess tissue fluid carried by lymphatic vessels
Properties of lymphatic vessels
One way system toward the heart
No pump
Lymph moves toward the heart

4. Harmful materials that enter lymph vessels
Bacteria
Viruses
Cancer cells
Cell debris
Lymph Nodes
Filter lymph before it is returned to the blood
Defense cells within lymph nodes
Macrophages—engulf and destroy foreign substances
Lymphocytes—provide immune response to antigens

5. Lymphatic Vessels Lymph capillaries
Walls overlap to form flap-like mini-valves
Fluid leaks into lymph capillaries
Capillaries are anchored to connective tissue by filaments
Higher pressure on the inside closes mini-valves
Fluid is forced along the vessel

6. Innate (nonspecific defenses) Adaptive (specific) defenses
Types of Defenses
Innate (nonspecific defenses)
Function the same way regardless of the pathogen type
Adaptive (specific) defenses
Immunity: targets certain pathogens
Based on body’s ability to distinguish “self” from “non-self”
Antigen – molecule that elicits an immune response

7. Nonspecific Defenses
Species resistance
Mechanical barriers
Chemical barriers
Fever
Inflammation
Phagocytosis

8. Inflammation
Redness from blood vessel dilation
Swelling from increased permeability of capillaries
Heat from increased blood flow
Pain

9. Phagocytosis
“Cell eating”
Performed by neutrophils and macrophages that form from monocytes

10. Development of Cells of Immunity
Fetal bone marrow forms lymphocytes
Lymphocytes differentiate:
In thymus  T cells
In marrow  B cells
T cells can form B cells
T and B cells circulate in bloodstream and are concentrated in lymph nodes and spleen

11. T Cell Types Helper T cells Memory T cells Cytotoxic T cells
Stimulate B cells to produce antibodies specific to an antigen
Memory T cells
Produced upon initial exposure to antigen but do not act until future exposure to the same antigen
Cytotoxic T cells
Destroy cancerous or virally-infected cells using perforin
Once activated, proliferate to increase clones

12. Primary vs. Secondary Immune Responses
Primary Immune Response
Occurs with first exposure to an antigen
Production and release of antibodies continues for several weeks
After primary response, memory T and B cells are produced
Secondary Immune Response
Occurs with future exposures to antigen
Faster response time

13. Primary Immune Response
Macrophages engulf invaders and present them to helper T cells in the nearest lymph node.

14. Cell-Mediated Immunity
T cells attach to foreign cells and:
a. Secrete toxins that kill target cells.
b. Secrete growth-inhibiting factors that prevent target cell growth.
c. Secrete interferon that inhibits proliferation of viruses and tumor cells.

15. Antibody-Mediated Immunity
Helper T cells activate B cells.
B cells produce clones (plasma cells and memory B cells) and antibodies.
Antibodies destroy antigen.

16. Adaptive Immune Responses
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17. Antibody Actions
Directly attach to antigen and destroy it
Label the antigen for destruction by macrophages
Stimulate localized changes that help prevent the spread of antigens

18. Secondary Immune Response
Same process as primary immune response with some exceptions:
Faster response time
Memory B cells produce clones quickly

19. Allergic Reactions
An immune attack against a non-harmful substance
May be caused by inherited tendency to overproduce IgE antibodies in response to certain antigens
IgE triggers the release of histamine  allergy symptoms
If reaction is severe  anaphylactic shock

20. Types of Immunity Naturally acquired active immunity
Develops after a primary immune response
Artificially acquired active immunity
Vaccine stimulates a primary immune response without causing symptoms
Artificially acquired passive immunity
Injection of antibodies; susceptibility may persist
Naturally acquired passive immunity
Antibodies passed to fetus from mother; persists 6 months to one year after birth
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21. When the immune system attacks “self” Examples of autoimmune diseases
Autoimmunity
When the immune system attacks “self”
Examples of autoimmune diseases
Multiple sclerosis - white matter of brain and spinal cord are destroyed
Type I diabetes mellitus - destroys pancreatic beta cells that produce insulin
Rheumatoid arthritis - destroys joints