Thymic Development of Autoreactive T Cells in NOD Mice Is Regulated in an Age-Dependent Manner

Abstract

Inefficient thymic negative selection of self-specific T cells is associated with several autoimmune diseases, including type 1 diabetes (T1D). The factors that influence the efficacy of thymic negative selection, and the kinetics of thymic output of autoreactive T cells remain ill-defined. We investigated thymic production of β cell-specific T cells using a thymus transplantation model. Thymi from different aged NOD mice representing distinct stages of T1D, were implanted into NOD.scid recipients and the diabetogenicity of the resulting T cell pool examined. Strikingly, the development of diabetes-inducing β cell-specific CD4+ and CD8+ T cells was regulated in an age-dependent manner. NOD.scid recipients of newborn NOD thymi developed diabetes. However, recipients of thymi from 7 and 10 d-old NOD donor mice remained diabetes-free, and exhibited a progressive decline in islet infiltration and β cell-specific CD4+ and CD8+ T cells. A similar temporal decrease in autoimmune infiltration was detected in some but not all tissues of recipient mice implanted with thymi from NOD mice lacking expression of the autoimmune regulator transcription factor, which develop multi-organ T cell-mediated autoimmunity. In contrast, recipients of 10 d or older thymi lacked diabetogenic T cells but developed severe colitis marked by increased effector T cells reactive to intestinal microbiota. These results demonstrate that thymic development of autoreactive T cells is limited to a narrow time-window, and occurs in a reciprocal manner compared to colonic microbiota-responsive T cells in NOD mice.

Isolation and Transplantation of Different Aged Murine Thymic Grafts.

“…As seen in Figure 2, the thymic graft should be placed atop the kidney, closest to the adrenal glands (anterior of kidney), on the opposite end from the capsular incision (posterior of kidney). A successful thymic transplant, when coupled with an appropriate hematopoietic environment, can remain productive in excess of 30 weeks 7 .…”

“…In vitro approaches such as reaggregate thymic organ cultures (RTOC) 6 , have proven to be useful for analyzing basic events associated with thymic selection, but fail to fully recapitulate the dynamics of ongoing in vivo events. As a result, this thymic transplantation-based approach was established to better study thymocyte selection events in vivo 7 . This protocol describes transplanting thymi from newborn and adult donor mice into immunodeficient scid recipient mice.…”

“…This technique permits the study of mechanisms that regulate positive and negative thymic selection, as well as thymic output of various T cell subsets during ontogeny. Most recently, this approach has been used to demonstrate that the efficiency of thymic selection is limited early after birth in mice leading to increased development of autoreactive T cells, and a reduced T cell repertoire specific for foreign antigens 7 .…”

Breaking through the central tolerance ceiling to unleash anticancer immune responses

“…Furthermore, the antigen specificity of T cells generated by the thymus is age-dependent. 9 Therefore, whether melanoma-reactive T cells continue to be generated in older mice requires clarification. Second, whether anti-RANKL antibody treatment will result in autoimmune side effects is not known.…”

Reestablishing T Cell Tolerance by Antibody-Based Therapy in Type 1 Diabetes

“…The breakdown of b cell-specific tolerance in the T cell compartment is complex, influenced by environmental, genetic, and age-dependent factors (Anderson and Bluestone 2005;Bach 1994;He et al 2013;Todd 2010). Dysregulation of peripheral tolerance mechanisms is thought to favor the differentiation and expansion of pathogenic effector T cells (Teff) versus immunoregulatory T cells (Treg) (Tisch and Wang 2008).…”