Hi Emmanuel, this reminiscent of the Heisenberg principle.
You can measure the concentrations of cytokines by ELISA, but you cant be sure if all those cytokines measured by ELISA are active and how they behave in bioassays.
You can do bioassays with all cytokines, but then you can't determine the concentrations of the cytokines. because many of them elicit the same response or opposite response.
Since there are more than 20 cytokine families coursing through your body at any time, you will have to choose carefully which ones to look at.