Immunology I - Mclean

Question 1

Innate immune system cells:

Answer 1

Macrophage
Dendritic cell
Mast Cell
Natural Killer cell
Granulocytes (basophil eosinophil neutrophil)
complement proteins
(fast response)

Question 2

Adaptive immune system cells:

Answer 2

B & T cells
(slow response)

B cells -> antibodies
T cells -> CD4+ T cell / CD8+ T cell

Question 3

Pus forming terminologies:

“need to know”

Answer 3

Suppurative
pyogenic
purulent

Question 4

Immunity -> branches into…

potential question

Answer 4

Immunity -> adaptive / innate
adaptive -> natural / artificial
natural (deliberate) -> passive (maternal)/ active (infection)
artificial (not deliberate) -> passive (antibody transfer) / active (immunization)

passive: getting antibodies
active: making antibodies

Question 5

How does innate system recognize pathogens?

know 2 terms involving recognition*** target

Answer 5

First step: recognition:

Pathogen associated molecular patterns (PAMPs) are on pathogens
Pattern recognition receptors (PRRs) on host cells

second step: recruitment:

Effector cells can come and kill pathogen
Complement proteins can be recruited via blood and assist in phagocytosis. Can lyse it too.

Question 6

Innate immune response to infection:

Answer 6

Causes inflammation.
Vasodilation, increased vascular permeability, infected tissue becomes inflamed causing pain, swelling, heat.

bacteria engulfed from effector cells, cytokine release, causes the vasodilation / inflammation.

Question 7

Types of innate immune responses:

Answer 7

acute inflammation
chronic inflammation
Granulomatous inflammation: (cant get rid of pathogen, so u just wall it off). Granulomas wall off.

Question 8

Mediators of innate immune response:

Answer 8

Cytokines: increase vasodilation, attract WBCs
Acute phase proteins: activate complement system, cell lysis. (C-reactive protein)
Bradykinins: Responsible in pain and itching.*****

Question 9

Mediators: Kinins (Bradykinin)
What is the function?

potential question

Answer 9

plays an important role in pain and itching
increase vasodilation
increase vascular permeability

Question 10

First line of defense:

what happens when it fails:

Answer 10

Innate: first line

acquired / adaptive / protective immunity: happens when fails

Question 11

Speed of innate vs adaptive:

Answer 11

innate: primary and secondary immune response same speed. Rapid initial response time.
Also: antigen nonspecific
adaptive: secondary immune response way faster than primary. Slow initial response time.
Also: antigen specific.

Question 12

Function:

B lymphocytes:

T lymphocytes:

Answer 12

B: synthesize / secrete specific antibodies. mediate HUMORAL immunity. (fluids of body used to be called humor, thus humoral. antibodies go around in fluids of body.)

T: recognize antigens presented by antigen presenting cells (APCs). Mediate cellular immunity.

Question 13

HIV selectively infects which type of cell?

Answer 13

CD4 T cells. results in loss of adaptive immune response.

Question 14

Progenitor cell of all the cells of the blood:

gives rise to:

Answer 14

Hematopoietic stem cell (HSC)
gives rise to:
1.) common lymphoid progenitor -> B / T cells / NK cells
2.) common myeloid progenitor
3.) common erythroid megakaryocyte progenitor -> megakaryocyte / erythroblast

Question 15

Myeloid cells: give rise to:

Answer 15

Granulocytes:
Neutrophils: phagocytosis
Eosinophils: provides defense against parasites such as worms
Basophils: allergic reactions

Question 16

B cells differentiate into…. which make…

Answer 16

B cells -> plasma cells -> make antibodies: soluble forms of Igs that are released into the blood and body fluids

Question 17

Primary lymphoid tissues:

Secondary lymphoid tissues:

Answer 17

primary: This is where lymphocytes develop and reach maturity. Examples:
B cells develop in bone marrow
T cells develop in thymus
secondary: where mature lymphocytes become stimulated to respond to pathogens. examples:
spleen, tonsils, adenoids, appendix, lymph nodes, peyer’s patches

Question 18

Draining lymph node:

Spleen:

Answer 18

lymph node receiving fluid from an infected site. afferent lymph vessels: deliver pathogens to the lymph node
efferent: lymph leaves lymph node

Spleen: The spleen is the only secondary lymphoid organ that filters damaged cells from blood.

Question 19

Lymphocyte mechanism: activation in secondary lymphoid tissue:

Answer 19

Dendritic cell carries engulfed bacterium (or bacterium just travels there).
Activates B cells to convert into plasma cells -> secrete antibodies
Naive T cells -> either helper T cells which help other cells, or cytotoxic T cells which kill cells

Question 20

antigen
immunogen
antigenicity
immunogenicity

define

Answer 20

antigen: an agent that can bind to components of immune system
immunogen: any agent capable of inducing an immune response.

Therefore, all immunogens are antigens, but not all antigens are immunogens.

antigenicity: ability to be antigenic
immunogenicity: ability to be immunogenic. Proteins are the best

Question 21

adjuvant:

epitope:

Answer 21

substance that u mix with an antigen or immunogen to make it more immunogenic.

epitope: part of an antigen to which an antibody would bind. on the antigen. (T cell receptor)
paratope: on the antibody. small region of antibodies which bind to epitopes. (MHC)

Question 22

T-independent antigen:
T-dependent antigen:

Answer 22

T-independent antigen: antigen binds to B cell. antibodies produced.
T-dependent antigen: requires presence of helper T cells to stimulate antibody production by B cells.

Question 23

tolerization
autoimmunity

definition:

Answer 23

tolerization: During development, pre B and T cells learn to differentiate between self / non self

autoimmunity: failure to differentiate between self / non self.

Question 24

Mature B cell (naive B cell): whats on surface

what about plasma cell:

Answer 24

IgD and IgM on surface

plasma cell: secreting the antibodies. IgM, IgG, IgA, IgE. Not so much IgD

Question 25

Which one of these antibodies, IgM, IgG, IgA, IgE, IgD, which one is more specific for protecting the mucosal surfaces of the oral cavity?

Answer 25

IgA, Dimeric form. U find this in saliva.

Question 26

MHC class I and MHC class II present itself to which T cells?

Answer 26

MHC class I - CD8 : killer
MHC class II - CD4 : helper

Question 27

2 major types of CD4 T cells: what they do?

Answer 27

TH1 cells: secrete cytokines at site of infection and activate macrophages. CELL MEDIATED RESPONSE.
viruses / bacteria favor th1 (much smaller, so phagocytosis)

TH2 cells: secrete cytokines in secondary lymphoid organs that primarily stimulate B cells to make antibodies to bind to extracellular pathogens and virus particles. HUMORAL IMMUNE RESPONSE

allergens / parasites favor th2

Question 28

What does the invariant chain protein do?

Answer 28

Prevents MHC class II from binding peptides in the ER.

Why is antigen not binding itself to MHC class II when both antigens are in ER?
MHC II binding groove blocked by invariant chain.

Question 29

Bare Lymphocyte syndrome:

Answer 29

rare disease characterized by defective TAP protein resulting in

poor cd8 t cell responses to viruses
mhc class I retention in ER. never received peptide antigen.

Question 30

What does the invariant chain protein do?

Answer 30

prevents MHC class II from binding peptides in the ER.

Question 31

Autograft
Isograft
Allograft
Xenograft

Answer 31

transplant from same individual.
transplant from twin
transplant from allogenic person (not identical)
transplant from different species

Question 32

Langerhans cells:

Answer 32

Macrophages of the skin that act like dendritic cells.

Question 33

IL-2

Answer 33

important cytokine for proliferation of T cells

T cells can produce IL2 for itself, stimulate itself.

Question 34

basic antibody structure:
Hinge region:
Fab:
F(ab’)2:
Fc region:

Answer 34

Hinge region: flexible region
Fab: antigen binding site, obtained by papain digestion
F(ab’)2 - obtained by pepsin digestion
Fc region: portion of the constant region that forms the “stem” of the Y shaped Ig molecule.

Pepsin: digests Fc region but makes F(ab’)2. the Fabs are still in tact
Papain: separates stem and 2 top parts (Fab)

Question 35

adjuvant:

Answer 35

substance that when mixed with an immunogen, enhances the immune response of the immunogen.

Question 36

Epitope vs paratope:

Answer 36

epitope on antigen
paratope on antibody

Question 37

which Ig can form polymers?

Answer 37

IgM and IgA.

IgM : can form pentamer
IgA: can form dimer

both linked to a J chain that can facilitate this polymerization.

Question 38

abundancies of 5 different isotypes of heavy chains:

Answer 38

Example: IgG1, IG2, IgG3, IgG4.

Lower the number, the more abundant it is.

Question 39

Are MHC peptide binding sites specific?

Answer 39

no. They have degenerate binding specificity - ability to bind several different sequences. (meanwhile TCRs are specific)

Question 40

MHC class I molecules vs MHC class II molecules:

Answer 40

MHC Class I: Present antigens of intracellular origins to CD8 T cells.
expressed by all cell types except erythrocytes. Meets mhc class I in ER.
“When a cell is infected, it shows itself via MHC 1”

MHC class II molecules: present antigens of extracellular origins to CD4 T cells.
expressed by antigen presenting cells (APC). Macrophages/B cells) Meets MHC class II in endocytic vesicle.

“When a cell deliberately takes up and phagocytosis a pathogen, it presents via MHC class II”

Question 41

Mature B cell (naive B cell): whats on surface

what about plasma cell:

Answer 41

IgD and IgM on surface

plasma cell: secreting the antibodies. IgM, IgG, IgA, IgE. Not so much IgD

Question 42

Variable region:

Constant region:

Answer 42

variable (V): responsible for binding pathogens. Differences here that accounts for different isotypes. The antigen-binding sites, the tips of the Fab regions.

constant (C): contains binding sites for receptors on phagocytes / complement proteins. The Fc region and half of the Fab regions.

Question 43

Light chains / Heavy chains in Igs:

Answer 43

2 identical H chains
2 identical L chains -> but theres 2 types. either 2 Lambda L chains or 2 kappa L chains.

Question 44

Hypervariable regions:
Framework Regions:

Answer 44

Hypervariable regions: high variability on antigen binding site. Sometimes called complementarity determining regions. This forms antigen binding site.
Framework Regions: relatively invariant regions.

Question 45

Neutralization
Opsonization:

Answer 45

neutralization: neutralizing antibodies directly inactivate pathogen / toxin by binding to it and preventing it from interacting with human cells. can endocytosis the toxin.

opsonization: some antibodies are opsonins, they function in opsonization, the coating of a pathogen. facilitates phagocytosis.

Question 46

IgM:
IgG:
IgA:
IgD:
IgE:

Answer 46

IgM: first antibody made. Good in agglutination
IgG: can pass through placenta. 80% of total Ig. **
IgA: Protects mucosal surfaces of oral cavity. Dimeric form does this. **
- monomeric form predominantly in serum.
IgD: little known activity
IgE: present on mast cells / basophils, protects against worms.

Question 47

Primary immune response: antibody content
Secondary immune response:

Answer 47

primary: first IgM released. Majority of it here. Some IgG.
secondary: Majority IgG. Some IgM.

Question 48

Somatic recombination:

Light chain:
Heavy chain:

types of segments in genome

Answer 48

Light: V and J segments
Heavy: VDJ segmenets

Somatic recombination: mixing of these different V’s, D’s, J’s can make billions of different antibodies.

Question 49

Allelic exclusion:

Answer 49

process of using genes from only one parental chromosome which assures that each B cell expresses only one type of heavy chain and one type of light chain. therefore, antibody of a single specificity.

Question 50

how to go from membrane to secretary form of Igs:

Answer 50

Alternate pattern of Heavy chain mRNA processing.

basically u just choose either the secretory codon (SC region) or membrane codon (MC region) in the genome.

Question 51

Somatic hypermutation:

Isotype switching:

Answer 51

Mutations occur in V genes of heavy / light chains. This leads to affinity maturation (more specificity for antigen).

Isotype switching: after encountering an antigen, can swap from IgG to IgA or IgE, etc. Thus, effector functions are different, but antigen specificity is the same.

Note: its the T cells that can do this isotype switching. (in T-dependent antigens, flashcard number 22).

Question 52

Mechanism of isotype switching:

Answer 52

Constant region that is closest to the VDJ region determines the Ig type. To swap to a different one, you loop out that region. Cannot go back.

Goes from IgM -> IgA
No switch regions between IgM and IgD. thats why u have them together from start.

Question 53

Development of T lymphocytes:

Answer 53

Goes from no receptors -> 2 receptors -> end up with 1 receptor (CD4 / CD8).

First you have positive selection of cells whose receptor binds to MHC molecules, then you have negative selection and death of cells that react too much with these MHC molecules or dont react at all.

1.) initially, its just a T cell. no CD4 or CD8
2.) Then you have a double positive. T cells have both CD4 and CD8
3.) Positive selection of cells whose receptor binds to MHC molecules. AKA: the cells that have a receptor will be selected.
4.) Therefore you end up both CD4s and CD8s.
5.) The T cells that failed to have a receptor to MHC will die.
6.) Later on, you will have death of cells that react too strongly with MHC.

SO: Initially, you wanna select cells that can interact with MHC I or MHC II. Then you wanna kill the ones that can’t interact. Then you want to kill the ones that react too much. (The ones that react too strongly can lead to autoimmunity)

Question 54

TCRs vs Igs:

Answer 54

TCRs:

TCRs only have one antigen binding site
TCRs are always surface receptors
no somatic hypermutation
no isotype class switching
can only interact with antigen via antigen presenting cells. not directly.

Question 55

Graft vs host disease

alloreaction

Answer 55

alloreaction: transplant rejection. kidney comes in, body rejects kidney

graft vs host disease: bone marrow transplant. new bone marrow attacks body.

Question 56

Professional antigen Presenting Cells:

Answer 56

Dendritic cells
Macrophages
B cells

Question 57

SUMMARY SLIDE:

Infection on foot. What happens after if innate response doesn’t solve the problem?

Answer 57

Infection causes innate response, if this doesn’t fix problem, dendritic cells / macrophages (APCs) will go to closest lymph node

when it enters afferent lymph vessel, B cells / T cells proliferate. These naive B / T cells can either:

form cytotoxic T cells
form helper T cells
B cells -> plasma cells, secrete antibodies.

Helper T cell can either become TH1, TH2.

TH1 -> help macrophages
TH2 -> help B cells

When CD4 TH2 cells bind with B cells, this is an advantage because they can undergo Isotype Switching.