Lecture 16 - Antibody classes and T cell mediated immunity

Question 1

what effect does IgG antibody binding have on phagocytosis?

Answer 1

enhances it

Question 2

what part of the antibody binds the antigen?

Answer 2

the hypervariable regions (epitopes) of the heavy and light chains

Question 3

what is the complement binding region?

Answer 3

the area of the antibody that complement binds to

Question 4

what are the types of antibodies classified by their heavy chains?

Answer 4

IgM
IgG
IgA
IgD
IgE

Question 5

which chain dictates the class of antibody?

Answer 5

heavy chain

Question 6

describe IgA

Answer 6

• the most abundant antibody in humans
• predominant class in sero-mucus secretions and blood
  looks like two ABs butt fuckin

Question 7

what is the main role of IgA?

Answer 7

to protect external body surfaces - barrier antibody
- also protects internal body surfaces such as the gut and GI tract

Question 8

describe IgD

Answer 8

• only trace amounts found in blood and other body fluids
• found almost exclusively on the surface of naiive B cells

Question 9

what is the main role of IgD?

Answer 9

• acts as a triggering receptor- delivers activation signal to naive B cells through antigen binding
• e.g helps activate B cells

Question 10

what is the unique thing about IgD?

Answer 10

rarely found in blood.
instead mostly bound bound to naiive B cells

Question 11

describe IgE

Answer 11

• small amounts in the blood
• important in allergies and parasitic infections

Question 12

what is the main role of IgE?

Answer 12

Its Fc region binds strongly to mast cell receptors and waits there until an allergen is found and binds to mast cell.

Question 13

how can we control allergies?

Answer 13

reduces amount of IgE circulating

Question 14

describe IgG

Answer 14

• dominant antibody type in blood and many other tissues
• opsonin
• monomeric structure?

Question 15

which Ig is passed onto babies by mothers to give protection of the baby after birth?

Answer 15

IgG
this is called passive immunity

Question 16

which IgGs are best at binding FcyR?

Answer 16

IgG1 and IgG3
- due to more flexible Fc regions

Question 17

what differentiates IgG1 from IgG2?

Answer 17

they have different Fc regions.
- this is why IgG1 will bind more strongly to immune cells such as neutrophils than IgG2

Question 18

describe IgM

Answer 18

• pentameric structure (valency of 10)
• largest AB (too big to be transported to placenta :((
• mostly confined to blood and lymphatics
• first primary AB response

Question 19

why is IgM the first primary AB response?

Answer 19

so it can bind as much bacteria as possible- slows and contains infections because it can bind lots of bacteria at once
- also an efficient complement activator

Question 20

T cells are very ?

Answer 20

special

Question 21

During naiive T cell activation, antigens must be p__________ and p___________

Answer 21

processed, presented

Question 22

what is a typical T cell antigen structure

Answer 22

small peptide sequences (8-17 aas)
- aka peptide antigens

Question 23

what is the only way T cells can be activated?

Answer 23

specialised antigen presenting cells

Question 24

how many different types of T cells do we have, and what is unique to each type?

Answer 24

millions
each type has its own TCR (t cell receptor)

Question 25

what is a clonal repertoire?

Answer 25

the number of different types of T cells we have that can bind their own specific antigens. the larger the number the better, average is >100 mil all the way up to 10 billion

Question 26

what is humoral immunity vs cell-mediated immunity?

Answer 26

humoral = B cells and plasma cells Cell mediated = T cell mediated

Question 27

true or false, T cells produce antibodies in the lymph nodes that are more specialized than antibodies produced by B cells

Answer 27

False, T cells to not make, produce or secrete antibodies

Question 28

which type of antigen are T cells most effective against?

Answer 28

intracellular antigens that are presented on the cell surface (MHC)

Question 29

which cell type is a major regulator?

Answer 29

T cells regulate and control other cells

Question 30

which cell type is the culprit in autoimmunity?

Answer 30

T cells

Question 31

what are the two subsets of T cells?

Answer 31

cytotoxic T cells Helper T cells

Question 32

what do cytotoxic T cells contain?

Answer 32

- CD8 (and so are CD8+) - T cell receptor - CD3

Question 33

what do helper T cells contain?

Answer 33

- CD4 - T cell receptor - CD3

Question 34

true or false, two peoples T cell repertoire can be identical

Answer 34

no, they are unique to everyone

Question 35

what is MHC vs HLA?

Answer 35

MHC is in mice, HLA is in humans

Question 36

which HLA do cytotoxic (CD8+) T cells recognise?

Answer 36

Class I HLA

Question 37

which HLA do helper T cells (CD4+) recognise?

Answer 37

Class II HLA

Question 38

true or false, the HLA genes are incredibly diverse and unique to each individual

Answer 38

true (unless youre an identical twin)

Question 39

where are HLA-antigen complexes formed?

Answer 39

formed inside the antigen presenting cells and then presented at cell membrane

Question 40

where are class I HLA molecules found?

Answer 40

on virtually all nucleated cells

Question 41

where are class II HLA molecules found?

Answer 41

On specialized antigen presenting cells and can be expressed by B cells

Question 42

what is the main source of antigens for class I HLA

Answer 42

Proteins within the cell being chopped up into fragments - such as a virus infection, bacteria or even vaccination products - smaller fragments than class II

Question 43

what is the main source of antigens for class II HLA

Answer 43

extracellular proteins that the cell phagocytosed. - larger fragments than class I

Question 44

which class of HLA can present multiple peptide fragments?

Answer 44

class II

Question 45

where are T cells undergo clonal activation?

Answer 45

in the T cell zone of the 2º lymphoid organs (lymph nodes)

Question 46

when does a T cell stop being naiive?

Answer 46

after recognising its antigen, but is still not fully activated yet

Question 47

how does a CD8+ T cell become fully activated?

Answer 47

a helper CD4+ T cell in the same space and time as the CD8+ sends helper signals such as IL-2 (and other interleukins)

Question 48

what happens to a CD8+ T cell after being fully activated?

Answer 48

proliferation and differentiation into the effector CD8+ T cells

Question 49

where to memory cells come from (T cells)

Answer 49

types of cytotoxic effector T cells

Question 50

where can antigens be 'hidden' from effector CD8+ T cells?

Answer 50

testes, ovaries and brain (blood brain barrier)

Question 51

true or false, a person with a viral infection in the ovaries will have the infection resolved by effector CD8+ T cells

Answer 51

false

Question 52

true or false, a person with a viral infection in the gut will have the infection resolved by effector CD8+ T cells

Answer 52

true