Immune Responses

Question 1

Name 3 types of harmful antigens

Answer 1

1. Autoantigens - start autoimmune response
2. Allergens
3. Alloantigens - other ppl i.e. transplant/transfusion

Question 2

What does “native” antigen mean, and which cell binds it

Answer 2

B cells bind ‘native’ antigens that are:

1. Not altered by other cells
2. In the ECF

Question 3

Where do dendritic cells present antigens

Answer 3

Travel via lymphatic vessels to regional lymph nodes

Lodge in T cell regions (particularly paracortical region) in which many T cells pass

Question 4

Which cells have MHC and what type of antigens can they present?

Answer 4

MHC1 (most cells) present endogenous antigens - viral proteins are trafficked to ER, then MHC1+antigen trafficked to cell surface

MHC2 (APCs - dendritic, B cells, macrophages) present exogenous antigens. Antigens moved into cell via endosome, then presented on cell surface

Question 5

3 improvements of the secondary antibody response compared to primary and why

Answer 5

1. Shorter lag time
2. Higher antibody conc.
3. Prolonged antibody conc. rise

T and B cells more numerous, and more mature in function (more IgG - higher affinity and smaller - cost benefit better)

Question 6

What can B cells do with and without help from T cells

Answer 6

Without help - short lived plasma cells IgM

With help - activated B cells differentiate in germinal centre

1. Class switching, to IgG, IgA, IgE
2. Somatic hypermutation - higher affinity by x1000

Question 7

Most lymphocyte malignancies are B cell origin. Name 3 stages of development (+location) that give rise to malignancy

Answer 7

1. Leukaemia - immature B cells in bone marrow
2. Lymphoma - mature B cells in 2nd lymphoid tissue, bone marrow and blood
3. Multiple myeloma - plasma cells in bone marrow

Question 8

How does MHC acquire diversity and what two features are important on a population level

Answer 8

3 MHC1 genes - HLA-A/B/C
3 MHC2 genes - HLA-Dp/Dq/Dr
These genes have many alleles!

1. Polymorphic genes - different alleles between individuals able to present different microbial peptides
2. Co-dominant expression - increases number of MHC molecules that can present peptides - therefore increasing likelihood of antigen presentation

Question 9

Two processes B cells undergo when activated

Answer 9

1. Class switching from IgM to IgG (or mucosal IgA)

2. Somatic Hypermutation - some mutations enable higher binding strength whilst antibody specificity is preserved

Question 10

Name the 5 antibody classes

Answer 10

IgM - primary response but does not persist
IgG - most abundant and provides memory
IgA - secreted by mucosal plasma cells
IgE - allergy
IgD