Introducing baselines for therapeutic use of regulatory T cells and cytokines in autoimmunity.

The concept of therapeutic immune regulation aiming to treat autoimmune diseases has been validated in multiple animal models, yet, the development of strategies for treatment of human autoimmune diseases remains problematic. Main obstacles are the contradictory findings in different model systems, as well as the contrasting functions of regulatory lymphocytes and cytokines. By drawing examples primarily from experimental type 1 diabetes, we propose that regulatory cells and cytokines can be classified according to the baseline at which they operate in healthy individuals and disease states that are not accompanied by severe systemic immune deficiency or skewing. Consequently, deletion or neutralization of regulatory cells or cytokines operative at high levels to maintain systemic homeostasis should constitute a therapeutic strategy for immune enhancement (e.g. tumor- and pathogen-specific immunity), whereas boosting these factors will have limited effects if the therapeutic goal is a downmodulation of immune responses (e.g. autoimmunity). Conversely, regulatory cells and cytokines operative at low homeostatic levels should unfold therapeutic capacities by further embellishment but not additional reduction.