20 November: Complement Cascade
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How does the host “know” that a pathogen is present?
Pathogen-associated molecular patterns (PAMPs) They basically say “look, you don’t belong here”
What are some examples of PAMPs?
LPS, peptidoglycan, lipoteichoic acid, lipid A, flagellin, pilin, viral and bacterial nucleic acid
What are PAMPs recognized by?
Pattern-recognition receptors, such as toll-like receptors (TLRs)
Where are TLRs present?
On macrophages, dendritic cells, neutrophils, and endothelial cells
Where are receptors located?
On the cytoplasmic membrane and the endoscope membrane (within a cell, such as the endoplasmic reticulum)
Toxic respiratory burst
Destroys toxic forms of O2 (H2O2, S.O.) Like oxyclean lol
Inflammation
The general, nonspecific response to tissue damage resulting from a variety of causes, including abrasions, cuts, and pathogens
What does inflammation cause within cells/
Gaps
Signs and Symptoms of inflammation
• Redness in light-colored skin • Localized heat • Edema (swelling): usually w/ heat + redness • Pain (ex. twisted ankle or infection)
Complement
Series of proteins in blood (C1, C2, C3….)
Classical pathway
Antibody-Microbe complex triggers complement cascade
Alternative pathways
Pathogen surface binds to C3
Lectin Pathways
Lectin-coated pathogen surface binds to C4 + C2
What do all the pathways activate?
C3 convertase
C3 convertase cuts C3 into what?
C3a and C3b, which have different functions
C3a
Capillaries, triggers inflammation, brings phagocytes that destroy bacteria along with antimicrobial peptides, interferons, complement, iron-binding proteins
C3b
Bind to bacteria, Opsonin
Opsonin
Enhances phagocytosis
Membrane Attack Complex (MAC)
C5b will land on bacteria + will bind to C6, C7, C8 + C9 and will form a circle in bacteria + ultimately make a hole The cell will lyse then die. (apoptosis)
Lymphatic System
Collects fluid from tissues + are filtered by lymph nodes + spleen
Slow eaters
Macrophages + dendritic cells Sloppy too (kill others around them)
Filopodia
What dendritic cells have; basically it “reaches blindly into a bag and grabs random things”
C3B
Activates C5 Convertase