IL-2, -7, and -15, but Not Thymic Stromal Lymphopoeitin,
Redundantly Govern CD4?Foxp3?Regulatory
T Cell Development1
Kieng B. Vang, Jianying Yang, Shawn A. Mahmud, Matthew A. Burchill,2Amanda L. Vegoe,
and Michael A. Farrar3
Common ? chain (?c)-receptor dependent cytokines are required for regulatory T cell (Treg) development as ?c?/?mice lack
Tregs. However, it is unclear which ?c-dependent cytokines are involved in this process. Furthermore, thymic stromal lympho-
poietin (TSLP) has also been suggested to play a role in Treg development. In this study, we demonstrate that developing
CD4?Foxp3?Tregs in the thymus express the IL-2R?, IL-4R?, IL-7R?, IL-15R?, and IL-21R? chains, but not the IL9R? or
TSLPR? chains. Moreover, only IL-2, and to a much lesser degree IL-7 and IL-15, were capable of transducing signals in
CD4?Foxp3?Tregs as determined by monitoring STAT5 phosphorylation. Likewise, IL-2, IL-7, and IL-15, but not TSLP, were
capable of inducing the conversion of CD4?CD25?Foxp3?thymic Treg progenitors into CD4?Foxp3?mature Tregs in vitro. To
examine this issue in more detail, we generated IL-2R??/?? IL-7R??/?and IL-2R??/?? IL-4R??/?mice. We found that
IL-2R??/?? IL-7R??/?mice were devoid of Tregs thereby recapitulating the phenotype observed in ?c?/?mice; in contrast, the
phenotype observed in IL-2R??/?? IL-4R??/?mice was comparable to that seen in IL-2R??/?mice. Finally, we observed that
Tregs from both IL-2?/?and IL-2R??/?mice show elevated expression of IL-7R? and IL-15R? chains. Addition of IL-2 to Tregs
from IL-2?/?mice led to rapid down-regulation of these receptors. Taken together, our results demonstrate that IL-2 plays the
predominant role in Treg development, but that in its absence the IL-7R? and IL-15R? chains are up-regulated and allow for IL-7
and IL-15 to partially compensate for loss of IL-2. The Journal of Immunology, 2008, 181: 3285–3290.
development of Tregs. These include signals emanating from the
TCR and the costimulatory molecule CD28 (2–5). In addition, sev-
eral studies have suggested that cytokines play a key role in this
process (6–11). However, which cytokines are involved has re-
mained controversial. For example, it has been known for many
years that mice lacking IL-2, or the IL-2R? or IL-2R? chains,
develop lethal autoimmune disease (12–14). This was initially at-
tributed to defective Treg development as these mice lacked
CD4?CD25?T cells. More recent studies using the transcription
factor Foxp3 as an identifier of Tregs found that young IL-2?/?
mice have relatively normal numbers of
D4?Foxp3?regulatory T cells (Tregs)4that develop in
the thymus play a key role in preventing autoimmune
disease (1). Multiple signals are required to induce the
CD4?Foxp3?Tregs (8, 15, 16). In contrast, both IL-2R??/?and
IL-2?/?? IL-15?/?mice exhibited significant decreases in Treg
numbers, suggesting that IL-2 and IL-15 play a redundant role in
Treg development (8, 9).
Importantly, although Treg differentiation is inhibited in IL-
2R??/?mice, Tregs are not completely absent (8, 9). This raises
the possibility that other cytokines can also drive Treg differenti-
ation. Along these lines, Watanabe et al. (17) have suggested a role
for the cytokine thymic stromal lymphopoietin (TSLP). Specifi-
cally, they suggested that TSLP production by Hassall’s corpuscles
plays an important role in human Treg development (17). Like-
wise, the common ?-chain (?c), which is closely related to the
TSLPR, has also been shown to be involved in Treg development.
For example, we and others have demonstrated that mice lacking
?c are devoid of Tregs (8, 15). The ?c forms a component of
multiple cytokine receptors including those for IL-2, IL-4, IL-7,
IL-9, IL-15, and IL-21 (18). Thus, two key questions in Treg de-
velopment are 1) which ?c-dependent cytokines can induce Treg
development and 2) whether TSLP signals are also involved in this
process. In this study, we demonstrate that developing Tregs ex-
press IL-2R?, IL-7R? and IL-15R? and respond to IL-2, IL-7, and
to a much lesser degree IL-15, by inducing STAT5 activation in
CD4?Foxp3?thymocytes. Similarly, IL-2-induced conversion of
CD4?CD25?Foxp3?thymic Treg progenitors into CD4?Foxp3?
mature Tregs. IL-7 and IL-15 also induced conversion of thymic
Treg progenitors into mature CD4?Foxp3?Tregs, albeit much
less effectively; in contrast, TSLP showed no activity in this con-
version assay. IL-4 signaling also does not appear to play a role in
Treg development as IL-4R??/?? IL-2R??/?mice show com-
parable numbers of Tregs as that seen in IL-2R??/?mice. In con-
trast, IL-2R??/?? IL-7R??/?mice exhibit a developmental
block which mimics that seen in ?c?/?mice. Finally, the
Center for Immunology and Department of Laboratory Medicine and Pathology, Uni-
versity of Minnesota, Minneapolis, MN 55455
Received for publication March 19, 2008. Accepted for publication June 29, 2008.
The costs of publication of this article were defrayed in part by the payment of page
charges. This article must therefore be hereby marked advertisement in accordance
with 18 U.S.C. Section 1734 solely to indicate this fact.
1This work was supported in part by a Pew Scholar Award, a Cancer Research
Institute Investigator Award, a Leukemia and Lymphoma Society Scholar Award, and
by National Institutes of Health Grant AI061165 to M.A.F. K.B.V. was supported by
a Supplement to Promote Diversity in Health-Related Research.
2Current address: Integrated Department of Immunology, National Jewish Medical
and Research Center, 1400 Jackson Street, K512C, Denver, CO 80206.
3Address correspondence and reprint requests to Dr. Michael A. Farrar, Center for
Immunology, University of Minnesota, 312 Church Street SE, 6-116 Nils Hasselmo
Hall, Minneapolis, MN 55455. E-mail address: email@example.com
4Abbreviations used in this paper: Treg, regulatory T cell; ?c, common gamma
chain; p-STAT5, phospho-STAT5; LMC, littermate control; TSLP, thymic stro-
Copyright © 2008 by The American Association of Immunologists, Inc. 0022-1767/08/$2.00
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3290CYTOKINE-DEPENDENT Treg DEVELOPMENT