Immunology

Question 1

What is the structure in the small intestine that contains lymphoid tissue?

Answer 1

Peyer’s patch

Question 2

Why doesn’t the Peyer’s patch have lymphatics coming IN, but going out?

Answer 2

Antigens come straight through the gut wall into the lymph nodes

Question 3

What is the isolated lymphoid follicle for?

Answer 3

B cell production

Question 4

What kind of cells are Peyer’s patches covered in?

Answer 4

M cells

at the dome of the payer’s patch

Question 5

How do M cells function

Answer 5

They are “ruffled” - surface area for antigens

M cells take up the antigen by endocytosis and phagocytosis

Antigen is transported across the M cells in vesicles

Released at basal surface

Antigen is bound by dendritic cells, which activate T cells

Question 6

What are the 2 distinct compartments of the mucosal immune system?

Answer 6

The epithelium and the lamina propria

Question 7

Lamina propria integrins

Answer 7

Sense whether adhesion has occurred

Question 8

What kind of cells are in the epithelium?

Answer 8

Intraepithelial Lymphocytes - cytotoxic T cells (CD8+)

Question 9

Once activated, where do T cells travel from the payer’s patch?

Answer 9

Drains via mesenteric lymph nodes to the thoracic duct

Return to gut via bloodstream

Question 10

What is α4:β7?

Answer 10

A gut homing effector

so the t cell makes its way back to the gut

Question 11

What does alpha 4: beta 7 bind to?

Answer 11

MAdCAM-1 on specific cells in the gut

Question 12

what kind of immunoglobulins does breast milk contain?

Answer 12

IgA

Question 13

Most common Immunoglobulin in the gut?

Answer 13

IgA

IgA1 in particular

Question 14

Is IgA monomeric or dimeric in the gut?

Answer 14

Dimeric

Question 15

Systemically, IgA is…

Answer 15

monomeric

Question 16

IgA in the gut…starting with an IgA secreting cell

Answer 16

> IgA secreting cell secretes IgA

> IgA binds to a receptor on the basolateral face of the epithelial cell.

> Via endocytosis and and transcytosis, the IgA makes its way to the apical face

> IgA is released + its secretory component

> The secreted IgA on the gut surface can bind and neutralise pathogens and toxins

> IgA is able to bind and neutralise antigens internalised in endosomes

> IgA can export toxins and pathogens from the lamina propria while being secreted itself

Question 17

How are the dimers connected in dimeric IgA?

Answer 17

a “J chain”

Question 18

Which other immunoglobin can do the same as IgA to an extent

Answer 18

IgM

Question 19

Do intraepithelial lymphocytes need to be primed?

Answer 19

NO

they are already active

Question 20

What can intraepithelial lymphocytes do to virally epithelial cells?

Answer 20

Infected cells display viral peptide to CD8 IEL via MHC class I

Activated IEL kills infected epithelial cell by PERFORIN/granzyme and Fas-dependent pathways

Prevents spreading and proliferation

Question 21

Epithelial cell stress - IEL resposne

Answer 21

Epithelial cells undergo stress as a result of damage et al and express MIC-A and MIC-b

NKG2D on IELs binds to MIC A & B and activates the IEL

Activated IEL kills the stressed cell via the perforin/granzyme pathway

Question 22

MIC-A and MIC-B are essentially flags for HELP

Answer 22

–

Question 23

What help regulate local hypo responsiveness?

Answer 23

Commensal organisms

PPAR Gamma

Question 24

What do bacteria do in regards to hypo responsiveness?

Answer 24

They mediate the generation of regulatory T cells

weak co-stimulation

Question 25

Bacteria can be recognised by TLRs on epithelial cells/leukocytes

Answer 25

This initiates a cascade

NF Kappa B makes its way into the nucleus to transcribe an inflammatory protein

BUT

Some commensal bacteria can block this gene transcription

Some commensal bacteria can block degradation of phosphorylated IkB preventing NFkB translocation to the nucleus

Question 26

What does NFϰB transcribe?

Answer 26

Cytokines, chemokines and defensins

Mediating an immune response

Question 27

Most defences are a balance between

Answer 27

protection and host damage

Question 28

What kills helminth infections?

Answer 28

IgE, mast cells and eosinophils

Question 29

What Interleukin causes B cells to produce IgE?

Answer 29

IL-4

Question 30

What cells does HIV actively infect?

Answer 30

Dendritic cells

These then shuttle the virus tor regional lymph nodes where they concentrate virus

Eventually infect CD4+ T cells

Question 31

CVID

Answer 31

Common Variable Immune Deficiency

Recurrent sinopulmonary & GI infections

failure to differentiate into Ig secreting cells

Low immunoglobulins all round

Question 32

Chronic Granulomatous Disease

Answer 32

Staph aureus/ inflammatory granulomas - pneumonia, liver abscess, perianal abscess and skin abscess.

Failure of phagocyte respiratory burst (NADPH oxidase produce ROS - this is missing)

Question 33

SCID

Answer 33

Severe combined immune deficiency

Defect in T and B cell immunity

No functioning adaptive immune response

Opportunistic infections

Question 34

Coeliac Disease

Answer 34

Gluten hypersensitivity

Gliadin

Both T cells and IELs destroy the gut

cytokine release leads to damage

–> Malabsorption and malnutrition

Flat mucosal surface

Question 35

Diagnosing coeliac disease

Answer 35

Biopsy

IgA Anti TTG autoantibodies presence

Question 36

Crohn’s is mediated by…

Answer 36

TH1 CD4+ T cells
Gamma interferon
IL-12
TNF-alpha

Question 37

Treatment of Crohn’s/UC

Answer 37

Anti TNF alpha