Hi Enrique - ATCC cell lines can be quite confusing (due to the number of sub-clones etc).
I have attached ATCCs list of Leukemic lines that they sell in case this helps.
From a brief glance at the literature however it seems that only a sub-population of Jurkat E6 cells are CD38 positive - and that to get 100% expression people have generated sub-clones from the Jurkat E6 cells (one attached -Munoz et al 2003).
Although they don't go into details they mention limiting dilution to generate CD38+ve clones which (if you have time) you might consider. This will also give you the CD38-ve population you also want.
We certainly found that the Jurkat E6 line was not 100% positive for CD4/CD8 etc.
Limiting dilution is straight forward but labour intensive (i.e. plate cells in a 96 well plate at a dilution of the cells to give 1 cell every 2-3 wells, grow until population is large enough for sub-culturing and analysis).
Alternatively you might want to contact the corresponding author and see if he will give you some.