Bioengineering

1
Bioengineering World Health

• Lecture Six

2
Review of Lecture 7

• Science
• Science is the human activity of seeking natural
  explanations for what we observe in the world
  around us.
• Engineering
• Systematic design, production and operation of
  technical systems to meet practical human needs
  under specified constraints
• Six steps of the engineering design method

3
Q3 How can technology solve health care
problems?

• CS1 Prevention of infectious disease

4
Roadmap of CS 1

• Science
• Organisms that cause disease
• Immunity
• Engineering
• How to make a vaccine
• Vaccines From idea to product
• Societal Impact
• Health and economics
• Ethics of clinical trials
• Developed world/Developing world

5
Pathogens

• How They Cause Disease

6
Types of Pathogens Bacteria

• Bacteria
• Cells with membrane and cell wall (usually)
• Can survive outside host
• Can reproduce without a host
• Can be killed or inhibited by antibiotics

7
How do Bacteria Cause Disease?

• Invade host
• Reproduce
• Produce toxins which disturb function of normal
  cells

8
Types of Pathogens Viruses

• Viruses
• Nucleic acid core with protein envelope
• Use host intracellular machinery to reproduce
• Cannot be killed with antibiotics
• gt50 different viruses that can infect humans

9
How do Viruses Cause Disease?

• Virus invades host cell
• Binds to cell membrane receptors
• Endocytosis brings virus into cell
• Virus takes over cell
• Use viral nucleic acid and host cell resources to
  make new viral nucleic acid and proteins
• More virus is released from host cell
• Virus causes host cell to burst OR
• Viral particles bud from host cell surface

10
(No Transcript)
11
Pathophysiology of HIV/AIDS
12
Pathophysiology of HIV/AIDS
13
Magnet Immunology Question

• Based on your understanding of the
  characteristics of bacteria and viruses identify
  which item best represents a bacterium, a virus
  and be able to explain why you chose each.

14
Magnet Immunology Answer
Bacteria
Virus
15
The Immune System

• How Are We Protected Against Pathogens?

16
Types of Immunity

• Keep pathogens out
• Kill them if they get in
• Three layers of immunity
• Physical Barriers
• Innate Immune System
• All animals possess
• Adaptive Immune System
• Vertebrates possess

17
Types of Immunity

• Physical Barriers
• Skin (2 square meters)
• Mucous Membranes (400 square meters)
• Innate Immune System
• Produces general inflammatory response when
  pathogens penetrate physical barriers
• Adaptive Immune System
• Can adapt to defend against any invader
• Important when innate immune system cannot defend
  against attack
• Provides immune system with memory

18
Physical Barriers
19
When Physical Barriers Fail

• Blood
• Plasma
• Cells
• Red blood cells
• White blood cells
• Platelets
• All of these cells are made in bone marrow from
  blood stem cells

20
http//www.medicinenet.com/leukemia/article.htm
21
White Blood Cells
Neutrophil Lymphocyte Macrophage
Defend the body against infectious disease
22
Innate Immune System

• Primarily effective against pathogens outside of
  cells
• Two main weapons
• 1) Professional phagocytes
• Cells that eat stuff
• 2) The complement system
• Proteins that tag stuff for destruction

23
Components of Innate Immune System

• 1) Macrophages
• Sentinels that patrol periphery
• If they find an invader, they become activated
• If activated, they
• Send signals to recruit other immune system cells
• Become vicious killers
• Present antigen to adaptive immune system (more
  on this later)

24
Components of Innate Immune System

• 2) Complement proteins
• Present in tissues blood
• Attach to surfaces of bacteria and viruses
• Target them for destruction by phagocytes
• Form Membrane Attack Complexes
• Recruit other immune cells from blood

25
What happens when you get a splinter?
26
What happens when you get a splinter?

• Pathogen makes it past a physical barrier
• Symptoms?
• Inflammatory Response red, swollen, hot, pus
• What causes these symptoms?
• Innate immune system is kicking into gear
• Usually innate immune system can take care of it

27
What happens when you get a splinter?

• Macrophages eat bacteria on splinter
• Phagocytosis
• Produce chemicals which
• Increase local blood flow
• Redness
• Heat
• Increase permeability of blood vessels
• Swelling
• Recruit other phagocytes to site of infection
• Pus

Click for video clip
28

29
Magnet Immunology Question

• Which magnet resembles a macrophage in your kit?

30
Magnet Immunology Answer
Macrophage
31
Adaptive Immune System

• Two main components
• Fight pathogens outside of cells
• 1) Antibodies
• Fight pathogens inside of cells
• 2) Killer T cells

32
What is an antibody?
Binds to antigens (foreign substance)
Binds to macrophage
33
Antibodies

• How are antibodies made?
• B cells
• Lymphocytes that make antibodies
• Have B cell receptors on surface
• 100 million different types of B cells, each with
  different surface receptors
• B cell receptors are so diverse they can
  recognize every organic molecule
• When a B cell binds antigen
• Proliferates - In one week, clone of 20,000
  identical B cells
• Secretes antibody

B-cell Proliferation
34
Magnet Immunology Question

• Which components of your kit are most like
  antibodies?

35
Magnet Immunology Answer
Antibodies
36
Magnet Immunology Question

• Arrange the components of the kit to demonstrate
  how these antibodies bridge a pathogen and the
  tool to kill it?

37
Magnet Immunology Answer
Macrophage
38
Adaptive Immune System Continued

• How do we kill virus once inside the cell?
• Antibodies cannot get to it
• Need T cells
• T Cells
• Three types of T Cells
• Killer T Cells (Cytotoxic T Lymphocytes CTLs)
• Helper T Cells
• Regulatory T Cells

39
How do T Cells ID Virus Infected Cells?

• Antigen Presenting Cells
• All cells have MHC molecules on surface
• When virus invades cell, fragments of viral
  protein are loaded onto MHC proteins
• T Cells inspect MHC proteins and use this as a
  signal to identify infected cells

40
Magnet Immunology Question

• Which magnet represents a normal host cell?
• Which magnet represents an antigen presenting
  cell?
• Using the components of the kit, demonstrate the
  two steps required for viral antigens to be
  presented on the MHC complexes on the surface of
  the blood cell.

41
Magnet Immunology Answer
Normal Host Cell
Antigen Presenting Cell (Infected Host Cell)
42
Magnet Immunology Question

• Which component resembles a T-cell?
• Demonstrate how the T cell can identify a virus
  infected cell.

43
Magnet Immunology Answer
T-Cell
44
Immunologic Memory

• First time adaptive immune system is activated by
  an antigen
• Build up a clone of B cells and T cells
• Takes about a week
• After infection is over, most die off
• Some remain memory cells
• Second time adaptive immune system is activated
  by that antigen
• Memory cells are easier to activate
• Response is much faster no symptoms

45
(No Transcript)
46
(No Transcript)
47
Putting it all together

48
(No Transcript)
49
(No Transcript)
50
Summary of Lecture 8

• Pathogens Bacteria and Virus
• Levels of Immunity
• Barriers ? First line of defense
• Innate ? Inflammation
• Phagocytes
• Complement
• Adaptive ? Immunologic memory
• Antibody mediated immunity
• Cell mediated immunity ? Pathogens within cells
• Diversity to recognize 100 million antigens