It was only after Prof. Sakaguchi identified the CD25 antigen in 1995 as a marker for a major population of T cells that had suppressor functions both in vitro and in vivo that the resurgence in the regulatory T cell area could begin.

The regulatory T cells field has grown dramatically over the past decade. It is now impossible to read a journal that does not contain numerous papers whose titles deal with regulatory T cells. More importantly, it is also difficult to submit a new research grant proposal in any area of immunologic research that does not include a section on analysis on the contribution of regulatory T cells to the subject matter under study.

Regulatory T cells can be best thought of today as "teenagers" ready to take on all the challenges of complex immune responses. In ten years, the field will certainly be more mature, and manipulation of regulatory T cell function by cellular biotherapy, antibodies and small molecules will be routine function of the clinical immunologist.

- From Preface by Prof. Ethan Shevach, National Institute of Health, USA

It has been for long debated whether suppressor/regulatory T cells did actually even exist. Today, this question is no longer accurate and the subject of regulatory T cells is the object of a constantly growing interest in immunologists and clinicians. There is no doubt that the history of Tregs will make a new big leap ahead.

- From Chapter One by Prof. Shimon Sakaguchi, Kyoto University, Japan