Chapter 2. Innate immunity

• The response to an initial infection Figure 2.1 - Innate immunity - Early induced response - Adaptive immune response

• The first line of host defense - Pathogens Figure 2 • The first line of host defense - Pathogens Figure 2.2 - Site of infection and protective immunity Figure 2.3 - Pathogens can damage tissues in a variety of different ways Figure 2.4

- An infection and the response Figure 2.5 Many barriers against infection Figure 2.6 Microbicidal chemical proteins ㆍlysozyme Figure 2.7 ㆍphospholipase A ㆍa-defensins (cryptdins) Figure 2.8 ㆍb-defensins Figure 2.9 ㆍq-defensins ㆍelastase ㆍC-type lectin ㆍCathelicidine

Specialized physical and chemical barriers of epithelia Figure 2.10

• The complement system and innate immunity - Lectin pathway - Classical pathway Figure 2.11 - Alternative pathway Figure 2.12 • C3 and C3 convertase C3a → induce inflammation C3b → binds pathogen surfaces - There are various types of C3 convertase depending on the complement pathway C3 C3 convertase

- mannose binding lectin • The lectin pathway - mannose binding lectin • binds to mannose and fucose residues of pathogens • collectin family • associated with MASP-1 and MASP-2 - MASP-1 : may cleave C3 (?) - MASP-2 : homologous to C1s ⇒ cleave C4, C2 - Ficollins ㆍhave fibringen-like domains ㆍspecific for oligosaccharidies containing acetylated sugar ㆍassociated with MASP-1 and MASP-2 Figure 2.14 Figure 2.15