Mucosal immunology

Question 1

What is MALT

Answer 1

Mucosal Associated Lymphoid Tissue
BALT = bronchial-associated
GALT = gut associated
SALT = skin associated

Question 2

What is a Peyer’s patch?

Answer 2

Peyer’s patch in small intestine, lots of immune cells, equivalent of lymph nodes

Question 3

Function of variable region

Answer 3

Binds to antigens on pathogen - epitope

Question 4

Function of heavy chain

Answer 4

Fc region , determines class of antibody

Question 5

Which antibody produced first ?

Answer 5

IgM

Question 6

Function of IgM

Answer 6

IgM: activate complement, neutralise antigens, forms immune complex

Question 7

Function of IgA

Answer 7

IgA: neutralises antigens, secretory, phagocytosis

Question 8

Function of IgG

Answer 8

IgG: complement activation, antigen neutralisation and phagocytosis

Question 9

Function of IgE

Answer 9

IgE: mast cell and eosinophil degranulation, anaphylaxis

Question 10

B cell activation and class switching

Answer 10

• B cell only makes one antibody which recognise one antigen
• Constant region of heavy chain determined by domains
• Mu codes for IgM
• B cell makes IgM first because first constant region is C(mu)
• AID caused by chemical activation - triggers class switching
• To switch, loops of DNA created between variable region and constant section that codes for IgA, these loops are then removed so first antibody is IgA

Question 11

IgA

Answer 11

• Secretory immunoglobulin and then lost
• Inhibits adhesion to epithelial cells - flexibility = bivalent binding to large antigen
• Neutralises toxins and viruses
• IgA mediated excretory pathway
• Doesn’t induce inflammation
• IgA antibody binds to poly-Ig receptor and is internalised - moved to external surface
• Secretory component wrapped around IgA

Question 12

How are B cells activated?

Answer 12

• Microbe detected by dendritic cells
• Dendritic cells display antigen on MHCii to TH2
• Signals cause CD4 to activate and make cytokines
• T helper cell activates B cell to make antibody
• B cells activates in lymph node or lymphoid tissue
• B cell goes through clonal expansion

Question 13

Function of TH2

Answer 13

Humoral and antibody response and parasitic response/allergy

Question 14

TH17 cell functions

Answer 14

Neutrophil recruitment

Question 15

T reg cells

Answer 15

Dampen down immune response - tolerance to self antigens etc

Question 16

Lymph nodes

Answer 16

Germinal cells are where B cells replicate and switch classes
Transcytosis: in M cells, antigens into vesicles, across cell, taken to dendritic cells and T cells

Question 17

Host-micWHat happens when you are born by c-section

Answer 17

Increased allergic response

Question 18

X-linked agammaglobulinaemia

Answer 18

• Present with upper respiratory tract/ear infections, often have GI symptoms and failure to thrive
• Severe infections with encapsulated bacteria
• Susceptibility to enteroviral infections
• Complete absence of B cells due to defect in Bruton’s tyrosine kinase

Question 19

COVID-19 response

Answer 19

• Virus infects host cell
• Creates intracellular responses
• Cytokines make dendritic cells
• Helper T cells differentiate into T helper cells etc
• They recognise infected cells on MHC i
• CD8 cytotoxic cells kill virus
• T follicular helper cells - lymph node, talk to B cells and cause them to differentiate to plasma cells and make antibodies - IgG and IgA to neutralise virus

Question 20

Antibiotic resistance

Answer 20

Immune development as normal
Antibiotics reduce gut diversity, disrupting homeostasis = reduced mucin, cytokines and AMP
Loss of diversity displaces dominant taxa and enables blooms of pathobionts and pathogens
Permeable epithelium increases risk for translocation of pathobionts and pathogens
Inflammatory gut environments and permanent compositional changes may lead to predisposition to chronic infections