The human body has multiple lines of defense against pathogens. The skin and mucous membranes provide the first line of defense through physical and chemical barriers. The second line of defense involves white blood cells that attack and destroy invading pathogens. The third and most specific line of defense involves antibodies and lymphocytes (B and T cells) that provide long-lasting immunity. B cells produce antibodies to target free pathogens for destruction, while T cells target infected cells through cell-mediated immunity. Antibiotics can treat bacterial but not viral infections by targeting bacterial processes without harming human cells. HIV attacks and destroys helper T cells, weakening the immune system and leaving the body vulnerable to opportunistic infections.

1. Defense against
Disease:
The Immune System
Some images courtesy of Steve Taylor…Bandung Intl. School

2. Essential Idea
The human body has
structures and
processes that resist
continuous threat of
invasion by pathogens.

4. PATHOGENS
• The immune system responds to the
presence of proteins not made by the
body.
• These proteins are called antigens.
• An antigen that causes a disease is
called a pathogen.
• Pathogen = disease causing
organism.

5. Pathogen vs. Non Pathogen

7. Method of Transmission
know a disease for each
• Air – “droplets”
• Direct contact – physical contact
• Through food
• Cuts in the skin
• Infected needles
• Blood transfusion
• Animals and Insects

8. Types of Pathogens
• Bacterial – Cholera, Tetanus
• Viral – HIV, polio, measles
• Fungal – Athlete’s Foot,
Yeast Infection,
• Protozoan - Malaria
• Worm – Tapeworm

13. Worms
• Worms are usually
ingested as eggs
• Found in minute
particles of feces
• Eggs hatch into larvae
• Can migrate out of the
intestines

14. Defense Against Disease

16. Body's Primary Line of Defense
NONSPECIFIC
• Skin – keratin on surface
• Mucous membranes – mouth,nose,
throat
• Tears - lysozyme
• Saliva - lysozyme
• Stomach Acid - acidic
• Urine

17. Skin

18. Blood Clotting/Clotting Factors
• To seal up “cuts” and prevent pathogen entry:
How:
– Platelets – small cell fragments
– Clotting factors released from platelets or damaged
tissue:
• Initiate production of THROMBIN (enzyme)
• THROMBIN converts FIBRINOGEN (protein) into FIBRIN
• FIBRIN forms a scab

20. Second Line of Defense
Counterattack!!!!!...will kill absolutely anything!!!
CELLS THAT KILL INVADING MICROBES:
Phagocytes:
• Recognize chemical receptors on foreign invaders – often
proteins
• Identifies and destroys pathogens: endocytosis: form
vacuole fuse with lysosomes and are digested
• Work in the blood – push through capillaries into tissue
– Work to control infection but can…
– Causes visible inflammation, heat, pus, fever (not over 105)…all
signs of infection

22. Ouch! - ANATOMY OF A SPLINTER!!

23. Types of White Blood Cells

25. Third Line of Defense:
Mounting a Specific Defense!!!!
Antibodies:
• Globular Protein
• Produced by the immune system to recognize and rid the body
of antigens.
•Lymphocytes –
• B – Cells –
• originate and fully mature in bone marrow.
• Destroys any “free” pathogen (not inside a cell)
• T- Cells –
• originate in the bone marrow. Move to mature in the Thymus.
• Destroys any body cells infected with a pathogen,
multicellular pathogens, and cancerous cells

26. Humoral vs. Cell Mediated
Immunity
• Type based on function of B and T cells.
• B – Cells - Humoral
• T – Cells v- Cell Mediated
• Both responses controlled by T-Helper Cells
• Activate both responses when presented with
an invading pathogen
• Pathogen must have antigen presenting cell
(APC)
• Macrophages and B- Cells = APC

27. Humoral and Cell Mediated Immunity
Feature Humoral Cell Mediated
Lymphocyte B- Cell T- Cells
Effector Cell B Cells
Plasma Cells
Cytotoxic T- Cells
Target Destroys all free
antigens
Destroys all
infected cells
Mode of Action Plasma cells produce
antibodies that surround
and neutralize pathogen
Cytotoxic T- Cells
release chemicals
that trigger apoptosis
Both types of immunity can produce memory cells that remain.

28. *

29. Production of Antibodies
1. Antigen is identified
2. Specific Plasma Cell (produced by B Cells) is identified
and activated by T-Helper Cells.
3. Specific Plasma cell clone.
4. Plasma cell produces specific type of antibody.
Shows some antibody on it cell surface.
5. Antigens bind to antibody…eliminate pathogen .
6. Some Clones (plasma cells) remain in blood.
7. Memory Plasma Cells – provide quick response
to invasion.

31. Antibiotics
• Bacteria vs. Virus
• Bacteria -
– Act against specific chemicals or chemical
pathways in prokaryotes.
– DO NOT affect Eukaryotic cells.
• Virus
– Viruses are “intracellular” parasites that
uses the host cell
– Drugs used against them also compromise
human cells (chemotherapy)

32. Florey and Chain’s
Experiments
SEE PAGE 290

33. Antibiotic Resistance
• Evolution of bacteria
• Resist antibiotics
• To Avoid Resistance:
– Prescribing for serious
conditions only
– Complete full course
– High standards of hygiene
– Remove antibiotics from
animal feed
– Develop new antibiotics

34. ANTIBIOTIC TUTORIAL

35. HIV and the Immune System

36. Retrovirus
Bacteriophage

37. HIV – Infection Process (Cause)
• Human Immunodeficiency Virus
• Attacks “Helper” T – Cells.
• Process:
• T – cells and HIV antigens bind
• HIV virus enters and replicates.
• T – cell ruptures releasing new viruses
• Viruses infect other T – cells
• Virus increases & T cells decrease
• Without Helper T- cells , lymphocytes cannot
form to produce antibodies.
• No Antibodies…the pathogen survives
• AIDS is a collection of diseases that result
from the lack of an immune response.

38. Animation: How the HIV Infection Cycle Works

39. HIV - Transmission
• Sexual relations – all forms
– Transmitted through small tears in soft tissue
• Sharing needles –drug use
• Contaminated blood transfusions
• Accidents
• Tattoos and Piercings

42. HIV DATA - THE WORLD
• Gapminder: Unveiling the bea

43. END