1. Immune System

2. Two nonspecific defense systems
First line of defense
Skin and mucous membranes
Second line of defense
Nonspecific cellular and chemical protection devices
(Third line of defense = specific immune responses to kill particular organisms)

3. First line of defense Skin and mucous membranes
Skin has 4 ways to block entry of disease
Structure
Dead, dried out keratinized cells – waterproof barrier
Continuously replaced –
pathogens get sloughed off
Acidic
pH 5-6 is hostile environment
Sweat glands produce antibodies
Dermicidin kills a wide range of harmful bacteria

4. Mucus and other secretions
Tears, saliva, earwax
Tears & saliva contain lysozyme = bacteria killer
Earwax traps particles
Mucus secreted in GI tract, respiratory tract mires microorganisms
Cilia beat constantly and sweep away pathogens (coughed up or swallowed)

5. Mucus and other secretions cont’d
Digestive and vaginal acids – low pH hostile environment
Vomiting, urination, defecation all remove microorganisms
Urine is acidic
Vomiting cleans the stomach
Diarrhea speeds pathogen expulsion

6. Nonspecific cellular and chemical defense
White blood cell army are Generalists – attack everything, clean up & repair crew
Phagocystosis – captures and digests
Neutrophils – first to respond, digest, destroy
Macrophages – engulf and digest large numbers of invaders
Eosinophils – cluster around large parasites and bombard with digestive enzymes

7. Inflammatory Response
Warmth, swelling and pain
Starts when tissue is damaged
Chemical stimulus calls mast cells to release histamine
Histamine capillaries  permeable  phagocytes to enter battle along with more blood
Extra fluid dilutes pathogens and toxins & brings in clotting proteins to wall off damaged area
Extra oxygen & nutrients promote tissue healing & carries away damaged cells, microorganisms & debris
Swollen tissue press on nerves causing pain  reduces movement

8. Adaptive (specific) defense system
Works in conjunction with the intrinsic:
it identifies the specific invader,
participates in the specific invader's destruction by either
killing them directly
activating the inflammatory response
activating complement proteins
making antibodies

9. Lymphocytes role
T cells participate in adaptive cellular defense (kill or help with the kill)
B cells make antibodies that help with the destruction of the invader

10. B-cell immune response.
Antibody mediated immunity
B cells (bone marrow) move to lymphatic tissues and become plasma cells (cells transported by the plasma) that produce antibodies (antibodies are proteins capable of inactivating antigens)
B cells must be activated by helper T cells
Antibodies are secreted into the blood, lymph and mucus – they combine with the antigen and mark them for destruction

12. B cell immune response cont’d
Once antibody production is enough to cause the antigen to disappear the development of the plasma cells stops
Some cells remain (memory B cells) in case of future invasion = active immunity

13. What is active immunity? How can it be acquired?
Occurs when b cells encounter antigens and produce antibodies
Artificially acquired – vaccine
Naturally acquired – natural contact

14. What is passive immunity? How do you get it?
Antibodies are obtained from the serum of an immune person
B cells do not produce new antibodies (there is no antigen challenge) – so no memory cells are made
Protection ends when donor antibodies degrade – but search and destroy while present
Mother to fetus, breast feeding
Snake bite serum, rabies shots