Lecture 4 (part II) Flashcards
Complement system
Plasma proteins work together to opsonize microbes, recruit phagocytes to infection site, and directly kill microbes
Early step 1 of complement activation
C3 convertase complexes form producing C3a and C3b
Early step 2 of complement activation
C5 convertase complexes form producing C5a and C5b
Late steps of complement activation
Form membrane attack complexes making holes in microbial membranes
Classical pathway
Requires IgM or IgG and C1 (Ab mediated)
C4bC2a = C3 convertase
C4bC2aC3b = C5 convertase
Lectin pathway
MBPs activate MASPS
C4bC2a = C3 convertase
C4bC2aC3b = C5 convertase
Alternative pathway
C3 undergoes spontaneous hydrolysis
C3bBb = C3 convertase (activated by factor D, B)
C3bBbC3b = C5 convertase (activated by Properdin)
Collectins
Soluble effector molecules in innate immune system; ex MBL, SP-A/SP-D in surfactant; inhibit growth, activate macrophages
Ficolins
Plasma proteins similar to colectins, but with carbohydrate recognition domain
What cytokines act locally on leukocytes and endothelium to induce acute inflammation?
TNF, IL-1
What cytokines mediate protective systemic effects of inflammation and increased production of leukocytes?
TNF, IL-1, IL-6
What are some pathological abnormalities resulting from systemic TNF?
Decreased cardiac function, capillary leak, thrombosis, metabolic abnormalities due to insulin resistance; all lead to septic shock
Pentraxins
CRP, SAP are acute phase proteins from this family; soluble plasma proteins that recognize microbial structures and participate in innate immunity
What is the function of IFN alpha/beta in response to TLR signaling and viral RNA sensors?
Bind to receptors on neighboring uninfected cells and activate JAK-STAT pathways that interfere with viral replication and enhance susceptibility for killing
How are innate and adaptive immunity linked?
Pathogen recognition via PRRs causing activation of APCs; innate immune response to microbe signals recognition by B cells
