BSCI 283 Lecture 20: Lecture 20

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Biological Sciences Program
BSCI 283
Daniel Stein

Host Defenses 1 4/24/17 • Host Responses o Cause inflammation and fever o Capsule splits and divides, virulence factors available temporarily while capsule grows o Virulence determinants secreted, are also found in cytoplasm of the cell (everything starts in the cytoplasm) o Ex. Streptococcus pneumoniae o Fever- systemic reaction o Triggers- endogenous pyrogen- cytokines released by macrophage after stimulation of TLRs o Cytokines-soluble regulatory proteins act as intercellular signals, include interleukins, interferons, chemokines o Endotoxin is an exogenous pyrogen- part of bacterial pathogen • Indirect Pathogen Recognition o Complement o Antibody mediated or complement mediated o Classical pathway: antigen and antibodiescomplement proteins 1,2,4complement cascade o Alternate Pathway-endotoxin and glycoproteinsfactors band D properdincomplement cascade o Complement cascade-actively killing bacteria o Alternate pathway is antibody independent, innate immunity • Complement Proteins o Contribute to defenses in several different ways o C3a and C5a-stimulate release of histaminedilation of blood vessels o C5a-attract nucleophiles and other phagocytes o C5b- form MAC o C3b-opsonize bacteria and other foreigners o All complements must work together in cascade o Complement had 3 main functions-inflammation, lysis of foreign cells (form membrane attack complex), opsonization • Specific Host Defenses o Adaptive-learned by experience o Not immediate-requires prolifer
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