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J. Exp. Med.,
Volume 189, Number 2, January 18, 1999 279-288
and
Interleukin 4 in the Prevention of Autoimmune
Thyroiditis in Rats by Peripheral CD4+CD45RC
Cells and CD4+CD8
Thymocytes
By
From the Medical Research Council Cellular Immunology Unit, Sir William Dunn School of
Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom
Previous studies have shown that induction of autoimmune diabetes by adult thymectomy and
split dose irradiation of PVG.RT1u rats can be prevented by their reconstitution with peripheral CD4+CD45RC
TCR-
/
+RT6+ cells and CD4+CD8
thymocytes from normal syngeneic donors. These data provide evidence for the role of regulatory T cells in the prevention
of a tissue-specific autoimmune disease but the mode of action of these cells has not been reported previously. In this study, autoimmune thyroiditis was induced in PVG.RT1c rats using a
similar protocol of thymectomy and irradiation. Although a cell-mediated mechanism has been
implicated in the pathogenesis of diabetes in PVG.RT1u rats, development of thyroiditis is independent of CD8+ T cells and is characterized by high titers of immunoglobulin (Ig)G1 antithyroglobulin antibodies, indicating a major humoral component in the pathogenesis of disease. As with autoimmune diabetes in PVG.RT1u rats, development of thyroiditis was
prevented by the transfer of CD4+CD45RC
and CD4+CD8
thymocytes from normal donors but not by CD4+CD45RC+ peripheral T cells. We now show that transforming growth
factor (TGF)-
and interleukin (IL)-4 both play essential roles in the mechanism of this protection since administration of monoclonal antibodies that block the biological activity of either of
these cytokines abrogates the protective effect of the donor cells in the recipient rats. The prevention of both diabetes and thyroiditis by CD4+CD45RC
peripheral cells and CD4+CD8
thymocytes therefore does not support the view that the mechanism of regulation involves a
switch from a T helper cell type 1 (Th1) to a Th2-like response, but rather relies upon a specific suppression of the autoimmune responses involving TGF-
and IL-4. The observation that the same two cytokines were implicated in the protective mechanism, whether thymocytes or peripheral cells were used to prevent autoimmunity, strongly suggests that the regulatory cells from both sources act in the same way and that the thymocytes are programmed in
the periphery for their protective role. The implications of this result with respect to immunological homeostasis are discussed.
;
interleukin 4
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