Abstracts (complete list) - Wissenschaft Online

Tim Sparwasser, Andrea Hartl, Katharina Lahl, Heinz Fehrenbach, Holger Garn, Harald
Renz, Hermann Wagner
Selective depletion of Foxp3+ cells in DEREG mice allows
functional analysis of regulatory T cells during experimental
allergic airway inflammation
Naturally occurring CD25+CD4+ regulatory T cells (Tregs) are currently intensively
characterized because of their major importance in inhibiting the development of
autoimmunity and allergy. Originally, CD4+ Tregs were identified exclusively by the
constitutive expression of CD25, and many in vivo experiments have been performed
using depleting antibodies directed against CD25. However, both the existence of CD25-
Tregs, especially within peripheral tissues, as well as the expression of CD25 on
activated conventional T cells, limits the interpretation of data obtained by the use of
anti-CD25 depleting antibodies. The most specific Treg marker is the forkhead box
transcription factor Foxp3, which has been shown to be expressed specifically in murine
CD4+ Tregs. To address the question of the in vivo role of Tregs in asthma
pathogenesis, we have generated bacterial artificial chromosome (BAC)-transgenic mice
named DEREG (depletion of regulatory T cells), expressing a diphtheria toxin receptor
(DTR) eGFP fusion protein under the control of the foxp3 locus allowing both detection
and inducible depletion of Foxp3+ Tregs. Similar frequencies and total numbers of CD25
+CD4+ Tregs, and comparable Foxp3 levels and suppressor function were observed
between DEREG and WT mice. Histological and flow cytometry analysis of spleen, lymph
node, and thymus revealed that the DTR-eGFP BAC transgene is specifically expressed
in Foxp3+CD4+ T cells. The injection of diphtheria toxin led to at least 90% depletion of
Foxp3+ Tregs and dramatically increased immune responses (DTH, OVA-immunization).
Using a model of acute ovalbumin (OVA)-induced allergic airway inflammation we can
demonstrate that depletion of Tregs during sensitization causes dramatically increased
Th2 pathology. Since our model for the first time allows specific depletion of Tregs
during acute immune responses without affecting activated effector T cells, our data
obtained in DEREG mice will shed light on the key cellular players involved in the
suppression of allergic airway inflammation.