Transcript Evolution of Immune Systems

Evolution of Immune Systems
Brunet, 1950:
Immunity = The ability to differentiate between
‘self’ and ‘non-self’
MHC-type Proteins are Present in all Metazoans
• Porifera have polymorphic ‘MHC genes” with
multiple loci
• MHC have no structural similarities to vertebrate
MHC - proteoglycan complex
Host Defence Systems in
Invertebrates
• Phagocytosis: Developed from procaryotic
feeding mechanism; Phagocytes present in
all phyla
• Encapsulation: Coelomocytes form a
capsule around larger foreign bodies
• Antibacterial peptides: Non-specific
response - no capacity for modulation;
Probably ubiquitous
Lectins
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Antibacterial proteins
Bind to sugar residues on microbe surfaces
‘Tagg’ microbes, which attracts coelomocytes
At least in vertebrates, lectins are sitting as
receptors on the cell surface of neutrophils.
Endothelial cells close to the infected tissue
are producing R-Selectin, a transmembrane
glycoprotein that bind lectins and activate the
neutrophils