Silke Schmidt writes- >I am testing neutrophil apoptosis in human whole blood after contact with >various polymers used at biomaterials. >I used AnnexinV assay with PI counterstaining and also TUNEL assay (without >counterstaining). >After 24 hours (which I found out to be a good timepoint,I get some results >that totally confuse me. >There is a group of polymers that cause high apoptosis rates in TUNEL assay >but low rates in AnnexinV assay and also very low necrosis rates. These are >the polymers that I know to be quite inert. > >On the other hand there are some polymers that strongly activate neutrophils >(for example their receptor expression and IL-8 production). They show low >apoptosis rates in TUNEL assay, high apoptosis rates in Annexin assay and >low necrosis rates. > >These results are reproducible with a very low standard deviaton... >But I simply cannot explain them! > >Does maybe anybody have a comment on this??? The whole concept of "neutrophil apoptosis" has bothered me for some time. A mature (polymorphonuclear) neutrophil has had its nucleus put through a wringer; it is incapable of cell division and I don't know how much transcription and translation it would logically be expected to do in the few days of life normal for the cell. Therefore, I would discount results of a TUNEL assay on neutrophils; they shouldn't have normal nucleic acid metabolism anyway, and focus instead on the Annexin assay. But I don't know; perhaps some neutrophil experts could follow up on this thread and enlighten both of us. -Howard
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