I know of people having had doctor controlled fasts in Bulgaria, where the RF, specific antibody levels and ESR had been monitored during and after fasts. In general these cases had tendency to increase the values of (worsen) the mentioned parameters, before they dropped (definitively) on raw food diet following the periodic 14-21-29 days fasts. They had done it on fruit-herbal tea-honey fasts. I theorize that the above dynamic would be more rapid under water-only-fasts.
I am referring to Dr. Emilova's experience. Her site is also available in English, but the videos with patients' testimonies are in Bulgarian language only, unfortunately.