Bought HEK293T cells from ATCC -- passage number question - (Jul/11/2013 )
A few months ago, someone accidentally threw away all of my frozen aliquots of HEK 293T cells (yes, it sucked). I use them to produce AAV and lentivirus. Anyway, I bought these from ATCC and they arrived today. The documentation says they are at passage number 17. Passage 17 is already a high passage number for me to attempt a transfection (I like it closer to passage no. 10). I've never purchased a cell line before; I have always gotten them from another lab (my old cells came from another lab with no more info than HEK293T passage number 7). It is normal to buys a cell line and have a higher passage number? Do I start with passage number 1 with purchased cell lines?
The parent line HEK293 has been around for a long long time and would most have been much higher than p17 when the T addition was made. The problem with passage number is that it is a bit lab dependent as to how it is measured, for instance many labs, when they get a line in, assign it as p0 - so it is likely that your p7 ones were actually much higher passage than 7.
There shouldn't be any problem with transfecting at much much higher passage numbers than you have been using.