BIO 343 Lecture Notes - Lecture 2: Mast Cell, Hemoglobinuria, Cd59
Immunology Chapter 2 Notes
Hayden Casassa
• Innate Immunity: The immediate response to infection
o Mechanism that are ready for action at all times and function from the very beginning of the
infection (0-4 hours)
o If successful, effects of the infection may not even be perceived by the human host
• Intracellular and extracellular pathogens require different types of immune responses
o Extracellular pathogens→ susceptible only to soluble immune molecules
▪ Antibodies, complement proteins
o Intracellular pathogens → susceptible to soluble molecules when microbes first enter the body
and when released the host cell dies
▪ Strategy is to kill the host cell in which they reside
o Virus is the only type of pathogen to be both intracellular and extracellular.
• The Complement System
o 30 plasma proteins
o complements the activity of antibodies
o Pre-dates antibodies in evolution (older)
o Functions by itself (innate immunity) or with Abs (Adaptive immunity)
o Poteis eoe oaletl attahed o fied to pathoge sufae
▪ Complement Fixation → refers to fact that protein permanently is linked to surface of
pathogen so its irreversible so complement protein is fixed
o The’e ade i lie ad iulate as iatie fo
o Work in a cascade and are activated sequentially
o C3 is the big complement protein
• C3 complement
o Key event is the cleavage of C3 into C3a and C3b
o C3b is the important one as it tags the bacterium for destruction and acts as opsonin
▪ Also can organize the formation of protein complexes to damage pathogens membrane
o C3a euits WBC’s
• Three Pathways of Complement Activation
o Alteatie Patha, Leti Patha, ad Classial Patha… ALC
o Each pathway is triggered differently but all end up with C3b attaching to pathogen
o Do’t all at at sae tie
o All are part of innate immunity but classical pathway is also part of adaptive since it can be
triggered by antibodies
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