Immunology 9- Host Defence Overview

Question 1

Special features of airway and lungs

Answer 1

Shared the pharynx with the GI tract

Rapid epithelial turnover

Filters blood volume every minute

Dissociated lymphocyte division (nodes)

Endopulmonary lymphatic circulation

IgA is important in the lung

Question 2

Surface defences against infection

Answer 2

Mechanical:
Epithelial tight junctions
Skin waterproofed by fatty secretions
Social conditioning (e.g. washing)

Chemical:
Fatty acids (skin)
Enzymes: lysozyme (saliva, sweat and tears), pepsin (gut)
Low pH (stomach, sweat)
Antibacterial peptides (Paneth cells in intestine)

Microbiological:
Normal flora compete for nutrients/attachment sites
Production of antibacterial substances

Question 3

Mucosal surface defences

Answer 3

Coughing

Sneezing

Mucus

Cilia

Rapid cell turnover

Wall of dead cells

Question 4

Interferons

Answer 4

When PAMPs an DAMPs are recognised, the cells produce interferons and a wave of informtion spreads out.

Type I/III: a/b/l 
Activates NK cells 
Upregulates MHC and Mx proteins 
Activates RNase L and Protein Kinase R (PKR) 
Induces anti-viral state 

Type II: IFNg
Proinflammatory
Th1 cytokine

Question 5

Defences against bacteria

Answer 5

Surface defences

Antibody opsonisation

Complement - causing lysis/opsonisation

Phagocytosis

Release of inflammatory mediators and acute phase proteins

Fever

Question 6

Defences against viruses

Answer 6

Surface defences

Interferons - VERY IMPORTANT AGAINST VIRUSES

Inflammatory mediators and acute phase proteins

NK cells

Antibody, complement, ADCC (antibody dependent cell-mediated cytotoxicity)

T cells

Question 7

Mucosal Defences

Answer 7

Mannan binding proteins

Antimicrobial peptides

Enzymes (e.g. lysozyme)

Mucosal lymphocytes

Secretory IgA

Special Antigen Sampling:
Waldeyer’s ring
Peyer’s patches
Dendritic cell networks