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Transcript
Failures of body’s defenses Immunopathology Evasion and subversion of the immune system by pathogens The immune system is still the big black box Environment Immune system Tolerance self Non-self Dangerous Pathogenic Little light at the end of the tunnel Immune response PATHOGENS HAVE SHORT GENERATION TIME PATOGENS Virus Bacteria 3 hrs Viruses 3 hrs Diversity Fast development parasites Humans have longer generation time, Need a sophysticated protection system Birth Development education Reproducrion at 35 Genetic variation prvents long-term immunity Highly variable capsular polysaccharide molecules---- serotypes High rate of mutation and recombination help influenza virus to escape immune recognition (Antigenic drift) ORIGINAL ANTIGENIC SIN High rate of recombination help influenza virus to escape immune recognition Large changes can occur rapidly by recombination between virus particles made in different hosts Viruses may interfere with the presentation of viral antigens (HSV, EBV, CMV, etc) Strategyies of Human cytomegalovirus (HCMV) Gene rearrangement is used by Trypanosomes to change cell surface antigens Cell surface glycoproteins are encoded by separate genes Approx. 1000 vatiable surface glycoproteins (VSG) Antibody controls parasite, but always a new variant emerges Deposition of immune complexes Inflammation CNS involvement, neuronal damage, sleeping sickness--- coma The pilin protein of Nesseria gonorrhoeae is also variable and only one is expressed at any time. ‘Seek and hide’ by Listeria monocytogenes, an intracellular bacterium Bacterial superantigens bridge α:β T-cell receptors and MHC class II molecules in the absence of a specific peptide. Macrophages are responsible for Phagocytosis of bacteria and other foreign cells and for activation of other immune cells Macrophage Bacteria Normally ingested bacteria and other things get sent to the lysosome for destruction by low pH and proteolysis Uh oh! bacterium But the TB bacterium has a better idea-It remodels the endosome to be its new home! Avoiding the lysosome also reduces presentation of bacterial peptides to the immune system by the MHC proteins