Yes, activated T cells do have slightly higher ATP levels than resting, however, when you titrate out the cell number there are no significant differences. i.e. the increase in ATP per cell upon activation is nowhere near as great as the effect of increasing the cell number. Often the increases in ATP upon activation are transient, with the MNC it was slightly different as the monocytes were the culprits they stuck to the plates and got a lot bigger (macrophage like). With lymphocytes it's very different. We have some data somewhere from Ivan Roitt's group, where they stimulated cells with PHA and then compared serial doubling dilutions of control cells and visualised it with the CCD camera and found no difference. We did a similar thing with neutrophils where we stimulated with FMLP and found no differences between conditions.