Construction of self-recognizing regulatory T cells from conventional T cells by controlling CTLA-4 and IL-2 expression

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 23; pp. E2116 - E2125
• Main Authors: Yamaguchi, Tomoyuki, Kishi, Ayumi, Osaki, Motonao, Morikawa, Hiromasa, Prieto-Martin, Paz, Wing, Kajsa, Saito, Takashi, Sakaguchi, Shimon
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 04.06.2013; National Acad Sciences
• Series: PNAS Plus
• Subjects: Analysis of Variance; Animals; Autoimmunity - immunology; Binding, Competitive; Biological Sciences; CD28 Antigens - metabolism; Cell Differentiation - immunology; CTLA-4 Antigen - metabolism; Dendritic Cells - metabolism; Enzyme-Linked Immunosorbent Assay; Flow Cytometry; Gene expression; Genetics; Immunity, Cellular - immunology; Inflammatory bowel disease; Inflammatory Bowel Diseases - immunology; Interleukin-2 - metabolism; Medicin och hälsovetenskap; Mice; Mice, Inbred BALB C; Mice, Transgenic; Microscopy, Fluorescence; PNAS Plus; T cell receptors; T-Lymphocytes, Regulatory - cytology; T-Lymphocytes, Regulatory - metabolism; thymic selection; immune tolerance; CD25
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1307185110

Thymus-produced CD4 ⁺ regulatory T (Treg) cells, which specifically express the transcription factor forkhead box p3, are potently immunosuppressive and characteristically possess a self-reactive T-cell receptor (TCR) repertoire. To determine the molecular basis of Treg suppressive activity and their self-skewed TCR repertoire formation, we attempted to reconstruct these Treg-specific properties in conventional T (Tconv) cells by genetic manipulation. We show that Tconv cells rendered IL-2 deficient and constitutively expressing transgenic cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) were potently suppressive in vitro when they were preactivated by antigenic stimulation. They also suppressed in vivo inflammatory bowel disease and systemic autoimmunity/inflammation produced by Treg deficiency. In addition, in the thymus, transgenic CTLA-4 expression in developing Tconv cells skewed their TCR repertoire toward higher self-reactivity, whereas CTLA-4 deficiency specifically in developing thymic Treg cells cancelled their physiological TCR self-skewing. The extracellular portion of CTLA-4 was sufficient for the suppression and repertoire shifting. It interfered with CD28 signaling to responder Tconv cells via outcompeting CD28 for binding to CD80 and CD86,or modulating CD80/CD86 expression on antigen-presenting cells. Thus, a triad of IL-2 repression, CTLA-4 expression, and antigenic stimulation is a minimalistic requirement for conferring Treg-like suppressive activity on Tconv cells, in accordance with the function of forkhead box p3 to strongly repress IL-2 and maintain CTLA-4 expression in natural Treg cells. Moreover, CTLA-4 expression is a key element for the formation of a self-reactive TCR repertoire in natural Treg cells. These findings can be exploited to control immune responses by targeting IL-2 and CTLA-4 in Treg and Tconv cells.