<prompt> All of the following are true about apoptosis excep:Expression of caspasesInternucleosomal cleavage of DNASmeared pattern of DNA fragmentationExpression of phosphatidyl serine  <response>: Ans: c Smeared pattern of DNA fragmentation Ref: Robbins, 7th ed, p. 27Smeared pattern of DNA fragmentation is indicative of necrosis and ladder pattern of DNA fragmentation on electrophoresis is indicative of apoptosisMorphological features of apoptosis:1 Cell shrinkage2 Chromatin condensation - most characteristic feature3 Formation of cytoplasmic blebs and apoptotic bodiesApoptotic bodies are round or oval bodies with eosinophilic cytoplasamand dense chromatin fragments4 Phagocytosis of apoptotic cells by macrophagesMechanism of apoptosis:Extrinsic pathway ot ApoptosisFas ligandBinds with three molecules of FASForms binding site for FAS associated death domainFADDFas associated death domain bindsActivation of caspases 8 Caspases 10 in humansActivation of execution caspases 3,6APOPTOSISIntrinsic pathwayWithdrawal of growth hormonestress or injuryLoss of BCL 2,BCL-XL antiapoptoticAccumulation of Bax ,Bim, Bid etc.Increasing permeability of mitochondrial membrane and leakage of proteinscytochrome cApoptosis inducing factorActivation of caspases 9Neutralisation of inhibitor of ApoptosisActivation of execution caspases 3,6APOPTOSISDifference between necrosis and apoptosisFeatureNecrosisApoptosisNucleusPyknosis,Karyorrhexis,KaryolysisFragmentation into nucleosomePlasma membraneDisruptedIntactCellular contentsEnzymatic digestion - contents may leak out of cellIntact; released as apoptosisAdjacent inflammationFrequentNilPhysiological pathologicalAlways pathologicalOften physiologicImportant points regarding apoptosis:Best known death receptor - TNF 1 receptor TNFR1 and a related protein called FAS CD 95Apoptotic cells express phosphatidyl serine and thrombospondin on their surfaceTumor marker of apoptosis - Annexin 5Intermediate molecule between death receptor andcaspases - SphingolipidceramideBRIDGEPyroptosis: Programmed cell death associated with antimicrobial responses during inflammation. It is studied in the context of Salmonella infected macrophages 