1. Immunity & Disease

2. What is DNA?

3. What is DNA Day?

4. What is DNA Day?
April 1953
Drs. James Watson and Francis Crick determined the structure of DNA (double helix)

5. What is DNA Day? April 1953 April 2003
Drs. James Watson and Francis Crick determined the structure of DNA (double helix)
April 2003
Human Genome Project determined the entire DNA sequence of a human (3 billion letters)

6. What is the Immune System?
Macrophage phagocytosing bacteria

7. The immune system protects the body from disease.
What is the Immune System?
The immune system protects the body from disease.
Macrophage phagocytosing bacteria

8. The immune system protects the body from disease.
What is the Immune System?
The immune system protects the body from disease.
What is a pathogen?
Macrophage phagocytosing bacteria
A macrophage engulfing bacteria

9. The immune system protects the body from disease.
What is the Immune System?
The immune system protects the body from disease.
What is a pathogen?
An infectious organism that can cause disease.
Examples: bacteria, viruses, fungi, and parasites
Macrophage phagocytosing bacteria
A macrophage engulfing bacteria

10. The immune system protects the body from disease.
What is the Immune System?
The immune system protects the body from disease.
What is a pathogen?
An infectious organism that can cause disease.
Examples: bacteria, viruses, fungi, and parasites
Macrophage phagocytosing bacteria
A macrophage engulfing bacteria
Are humans the only ones with an immune system?

11. The immune system protects the body from disease.
What is the Immune System?
The immune system protects the body from disease.
What is a pathogen?
An infectious organism that can cause disease.
Examples: bacteria, viruses, fungi, and parasites
Macrophage phagocytosing bacteria
A macrophage engulfing bacteria
Are humans the only ones with an immune system?
No, other mammals, plants, fish, reptiles, and insects all have immune systems.

12. What happens when we get an infection?
Our immune system destroys the pathogen in 2 ways

13. What happens when we get an infection?
Our immune system destroys the pathogen in 2 ways
1. Cell-mediated response – involves our immune cells to destroy pathogens
Examples:
Macrophage
Neutrophils
Eat pathogens and debris
Eat pathogens and kill by releasing toxic particles

14. What happens when we get an infection?
Our immune system destroys the pathogen in 2 ways
2. Humoral response – destroy pathogens using antibodies produced by B cells

15. What is an antibody? What happens when we get an infection?
Our immune system destroys the pathogen in 2 ways
2. Humoral response – destroy pathogens using antibodies produced by B cells
What is an
antibody?

16. Antibodies are Proteins
Information is stored in DNA
RNA Synthesis
(transcription)
RNA copy
Protein Synthesis
(translation)
Gene = segment of DNA that tells the cell how to make a certain protein.
Proteins work together to form the functional machinery that makes up a cell.
The central dogma of molecular biology was established by Francis Crick in 1958.
The Central Dogma states that DNA provides the instructions for making RNA, and RNA then provides the instructions for making protein. The overall concept of protein synthesis is basic, but the details of this process are quite complex and we wont go into those today.
Basically DNA information is copied into messenger RNA (mRNA) by the process known as transcription and proteins are synthesized using the information in the mRNA as a template in a process known as translation.
Can anyone tell me one of the differences between DNA and RNA? Bases: Thymine (DNA) and Uracil (RNA)
Here are all the ways they differ:
･They differ in composition:
1.The sugar in RNA is ribose, not the deoxyribose in DNA.
2.The base uracil is in RNA instead of thymine.
･They also differ in size and structure:
1.RNA molecules are smaller (shorter) than DNA molecules,
2.RNA is single-stranded, not double-stranded like DNA.
･Another difference between RNA and DNA is in function. DNA has only one function-STORING GENETIC INFORMATION in its sequence of nucleotide bases. But there are three main kinds of ribonucleic acid, each of which has a specific job to do.
1.Ribosomal RNAs-exist outside the nucleus in the cytoplasm of a cell in structures called ribosomes. Ribosomes are small, granular structures where protein synthesis takes place. Each ribosome is a complex consisting of about 60% ribosomal RNA (rRNA) and 40% protein.
2.Messenger RNAs-are the nucleic acids that "record" information from DNA in the cell nucleus and carry it to the ribosomes and are known as messenger RNAs (mRNA).
3.Transfer RNAs-The function of transfer RNAs (tRNA) is to deliver amino acids one by one to protein chains growing at ribosomes.
Protein
Amino acids
Proteins do most of the work in a cell and provide much of its structure

17. Antibody Structure Variable Region: Part of the antibody
that binds Pathogens
Heavy Chain
Constant Region
Light Chain

18. Prevent pathogens from binding cells
What do Antibodies do?
Prevent pathogens from binding cells
Bacteria
Bacteria

19. 2. Help other cells recognize pathogens so they can eat them up
What do Antibodies do?
2. Help other cells recognize pathogens so they can eat them up
Bacteria
Bacteria
Bacteria
Bacteria
Bacteria
Neutrophil
Macrophage

20. Questions…
Name some pathogens that can infect us and cause disease?

21. Questions… Name some pathogens that can infect us and cause disease?
If there are several types of pathogens, do they all look similar or different?

22. Questions… Name some pathogens that can infect us and cause disease?
If there are several types of pathogens, do they all look similar or different?
If there are several pathogens different from each other, how do our antibodies recognize and bind all of them?

23. Immunity Demonstration
One student has on black gloves, one student with purple gloves, two students with no gloves. Dump out purple and black balloons and teach concepts of valence, specificity, etc. See antibody activity handout.

24. There are LOTS of different pathogens
There are LOTS of different pathogens. How does our immune system recognize them all?
As we discussed before the break, there are many, many different pathogens our bodies might have to fight off. And as you saw from our game, it’s important that we have antibodies that are able to recognize each of these different pathogens. So how does that work? How can our immune system recognize so many different pathogens?

25. B cells are the cells of the immune system that make antibodies
Remember….
B cells are the cells of the immune system that make antibodies
Remember, B cells are the cells of our immune systems that make antibodies, which are the proteins that are able to recognize pathogens.

26. Each B cell produces a unique antibody that recognizes a specific piece of foreign material (e.g., pathogen)
Pathogens
Antibodies
Not all B cells are making the same antibodies, however – in fact, every B cell makes a unique antibody, and is therefore able to recognize a unique pathogen. These antibodies differ from each other in their variable regions - that’s the part of the antibody protein that specifically interacts with proteins on the pathogen’s surface.
B cells
The different antibodies are unique from each other by having
different variable regions!

27. How do B cells produce different variable regions of antibodies?
Our B cells can make 1011 different antibodies.
Amazingly, our B cells are able to generate 100 Billion different antibodies! If you remember, proteins like antibodies are encoded by genes in our DNA – so do you think we have a single gene for each individual antibody our B cells produce?
How many is this?

28. How do B cells produce different variable regions of antibodies?
Our B cells can make 1011 different antibodies.
Amazingly, our B cells are able to generate 100 Billion different antibodies! If you remember, proteins like antibodies are encoded by genes in our DNA – so do you think we have a single gene for each individual antibody our B cells produce?
How many is this?
100,000,000,000

29. The entire human genome contains about 30,000 genes
Could it be that in our DNA we have a gene for each of these 1011 antibodies?
The entire human genome contains about 30,000 genes
Well, the entire human genome has been sequenced, and our entire genomes only contain 30,000 genes – not enough to encode all of those 100 Billion different antibodies. And of course, most of those genes have to be making other proteins, right? So how do our B cells make so many different antibodies?

30. The entire human genome contains about 30,000 genes
Could it be that in our DNA we have a gene for each of these 1011 antibodies?
The entire human genome contains about 30,000 genes
30,000 <<< 100,000,000,000
(30,000 is much less than 100,000,000,000)
Well, the entire human genome has been sequenced, and our entire genomes only contain 30,000 genes – not enough to encode all of those 100 Billion different antibodies. And of course, most of those genes have to be making other proteins, right? So how do our B cells make so many different antibodies?

31. Every cell in your body has the exact same genetic information encoded in your DNA
Gene A
Gene B
Gene C
Gene D
Skin cell
Gene A
Gene B
Gene C
Gene D
First, it’s important to understand that even though every cell in your body contains the exact same set of DNA – that is, every cell has those same 30,000 genes of the complete genome – different cells do different things with that DNA.
B cell
Gene A
Gene B
Gene C
Gene D
Nerve cell

32. However, different cells have different genes turned on or off
Gene A
Gene B
Gene C
Gene D
Skin cell
OFF
OFF ON
OFF
Gene A
Gene B
Gene C
Gene D
For example, in a nerve cell, a lot of genes are turned off – that is, they’re not making proteins. Nerve cells will turn on the genes that are important for their job as part of the nervous system – so they may turn on genes to make proteins that will act as neurotransmitters (examples of neurotransmitters) – but they’ll turn off other genes for proteins they don’t need – a nerve cell has no need to make collagen like a skin cell does. This is true for B cells too – they specifically turn on a set of genes that are important for their job – fighting off pathogens.
B cell ON
OFF
OFF ON
Gene A
Gene B
Gene C
Gene D
Nerve cell

33. How do B cells produce different variable regions of antibodies?
Part of the answer is that….
In the DNA of B cells, specific antibody genes are turned on.
OFF
OFF ON
OFF
So in B cells, there is a set of genes that is important for making antibodies that is turned on, even those those same genes are inactive in other cells. This allows B cells to manipulate the genes for antibodies in a very unique way, allowing them to generate billions of different antibodies from much fewer genes.
Gene A
Gene B
Gene C
Gene D

34. How do B cells produce different variable regions of antibodies?

35. How do B cells produce different variable regions of antibodies?
We are able to make so many different antibodies due to another phenomenon called VDJ Recombination

36. How do B cells produce different variable regions of antibodies?
We are able to make so many different antibodies due to another phenomenon called VDJ Recombination
VDJ recombination is the process by which V, D, and J genes are randomly selected and combined to form the heavy and light chains that make antibodies.

37. How do B cells produce different variable regions of antibodies?
We are able to make so many different antibodies due to another phenomenon called VDJ Recombination
VDJ recombination is the process by which V, D, and J genes are randomly selected and combined to form the heavy and light chains that make antibodies.
VDJ recombination is specific to certain cells of the immune system and does not occur in other cells of our body.

38. Genes that encode antibody proteins are found in DNA
Antibodies are made up of 2 light chain proteins and 2 heavy chain proteins.

39. Genes that encode antibody proteins are found in DNA
Antibodies are made up of 2 light chain proteins and 2 heavy chain proteins.
The genes that encode these proteins are found in your DNA.  These are referred to as V, D, and J genes. V V D D V V J J J J

40. There are 45 V, 27 D, and 6 J genes in the heavy chain DNA sequence

41. Through VDJ recombination, the cell randomly chooses 1 V, 1 D, and 1 J gene to make the heavy chain
In this example, the heavy chain DNA randomly recombines to join the V36 and the D5 genes.
V38 D3
V39 D2
V40 D1
D20
D21
D25
D24
D23
D22
D22
D21

42. The cell randomly chooses 1 V, 1 D, and 1 J gene to make the heavy chain
In this example, the heavy chain DNA randomly recombines to join the V36 and the D5 genes.
V37 D4
V38 D3
V39 D2
V40 D1
D20
D21
D25
D24
D23
D22
D22
D21

43. The cell randomly chooses 1 V, 1 D, and 1 J gene to make the heavy chain
Then, the heavy chain DNA randomly recombines to join the D5 and J3 genes.

44. The cell randomly chooses 1 V, 1 D, and 1 J gene to make the heavy chain
Then, the heavy chain DNA randomly recombines to join the D5 and J3 genes.

45. DNA → RNA → Protein Only the V36, D5 and J3 genes are turned ON.
Heavy chain DNA
Transcription
Only the V36, D5 and J3 genes are turned ON.
The remaining heavy chain genes are turned OFF.
V36
Heavy chain mRNA
Translation
V36
Heavy chain protein

46. Antibodies made and assembled in B-cells
Heavy and light chain proteins are translated

47. Antibodies made and assembled in B-cells
Heavy and light chain proteins are translated
Heavy and light chain proteins are assembled into antibodies within the cytoplasm

48. Antibodies made and assembled in B-cells
Heavy and light chain proteins are translated
Heavy and light chain proteins are assembled into antibodies within the cytoplasm
Antibodies are exported to the cell surface where they can recognize pathogens

49. The inability of immune cells to perform VDJ recombination has very serious consequences!
Individuals with a defect in VDJ recombination, lack diversity in their antibody production, and as a result have severely weakened immune systems (immunodeficiency)

50. Once a B cell recognizes a pathogen, how does it trigger an immune response?
Helper T Cell
Activation
B Cell
virus
This activation leads to the release of antibodies and clonal expansion.

51. VDJ Recombination Game

52. One student in each group will secretly create a unique pathogen
Example Pathogens!

53. One student in each group will choose one V, D and J gene to create a unique B-cell

54. The B-cell has FOUR chances to correctly match the pathogen!✔ V1 D2 J3 = + +

55. Please PAUSE and take a moment to play the VDJ recombination game
l l

56. A clone is an exact genetic copy of another cell.
One B cell isn’t going to release enough antibody on its own to fight a pathogen. So it makes clones of itself.
A clone is an exact
genetic copy of
another cell.

57. Clonal expansion
An activated B cell that has come in contact with its corresponding pathogen and helper T cell will go through clonal expansion.
1000 B cells that recognize the pathogen
When a B cell comes into contact with the pathogen that its antibody recognizes, it begins to divide to make an exact copy of itself. Then those cells divide to make more copies, and on and on.
4-5 days

58. Immunity Demonstration

59. Memory B Cells
After clonal expansion, some B cells turn into memory B cells.
These cells will remain in your body for years, ready to respond immediately if you encounter that pathogen again.

60. Memory B cells protect us from future infections…
Can we take advantage of memory B cells to prevent ourselves from getting sick?

61. Vaccines help our bodies create memory B cells without making us sick
Image from:

62. Vaccines contain non-infectious versions of a pathogen:
How do vaccines work?
Vaccines contain non-infectious versions of a pathogen:
Subunit
vaccines
Killed
vaccines
Modified live
vaccines

63. Vaccines contain non-infectious versions of a pathogen:
How do vaccines work?
Vaccines contain non-infectious versions of a pathogen:
Subunit
vaccines
Killed
vaccines
Modified live
vaccines
These incomplete or weakened versions won’t make us sick, but our body will still mount an immune response against them, creating memory B cells in the process.

64. Name some diseases we are vaccinated against?
Examples include: Measles, Mumps, Rubella, Yellow fever and Chicken Pox vaccines.
Because virus is still replicating (growing), these types of vaccines are very effective at eliciting an immune response.
Once students say FLU, move to the next slide.

65. Why do we have to get the flu vaccine every year?
Often, large disease outbreaks (pandemics) occur when a virus that normally infects another species, acquires a mutation that enables it to infect humans. Since human immune systems have not seen this specific pathogen before, there are no “memory cells” in the population, and therefore large numbers of individuals get sick. In the case of swine flu (H1N1), scientists believe that genes from flu virus that infects swine, chickens, and humans combined to form a new version of the virus that was infectious for people.

66. H1N1 Influenza Virus
Often, large disease outbreaks (pandemics) occur when a virus that normally infects another species, acquires a mutation that enables it to infect humans. Since human immune systems have not seen this specific pathogen before, there are no “memory cells” in the population, and therefore large numbers of individuals get sick. In the case of swine flu (H1N1), scientists believe that genes from flu virus that infects swine, chickens, and humans combined to form a new version of the virus that was infectious for people.
Neumann et al. Nature 2009

67. What did we learn today?

68. What did we learn today?
Antibodies are proteins created by B cells that bind to pathogens, a key step in our immune response.

69. What did we learn today?
Antibodies are proteins created by B cells that bind to pathogens, a key step in our immune response.
We are able to create a large variety of antibodies using VDJ Recombination and turning genes on and off.

70. What did we learn today?
Antibodies are proteins created by B cells that bind to pathogens, a key step in our immune response.
We are able to create a large variety of antibodies using VDJ Recombination and turning genes on and off.
B cells mount an immune response by undergoing clonal expansion.

71. What did we learn today?
Antibodies are proteins created by B cells that bind to pathogens, a key step in our immune response.
We are able to create a large variety of antibodies using VDJ Recombination and turning genes on and off.
B cells mount an immune response by undergoing clonal expansion.
We are protected from future infections by memory B cells.

72. What did we learn today?
Antibodies are proteins created by B cells that bind to pathogens, a key step in our immune response.
We are able to create a large variety of antibodies using VDJ Recombination and turning genes on and off.
B cells mount an immune response by undergoing clonal expansion.
We are protected from future infections by memory B cells.
Vaccines are a method of creating memory B cells without causing illness.

73. About the Scientist: What do I study? Why do I love science?
Questions?