Yes. I don't think there is any good evidence of cortisol levels that are abnormal (given the average lifestyle of people with ME/CFS - waking later, no morning rush) or that the production of cortisol in response to stressors is abnormal. I see that @arnoble has been directed to our thread on cortisol here already, on another thread, but link it here again for completeness.
I suppose bursts of cortisol may contribute to the effect of adrenalin in activating t-cells - I haven't looked to see if it does cortisol does that too.