Suppressor T cells regulate the nonanergic cell population that remains after peripheral tolerance is induced to the Mls-1 antigen in T cell receptor Vβ8.1 transgenic mice

We have found suppressor T cells that inhibit the proliferative response of naive CD4+ T cells in T cell receptor (TCR) Vβ8.1 transgenic mice rendered tolerant in vivo by inoculation of Mls-1a-positive cells. This suppression was mediated by CD4+ T cells but not by CD8+ T cells or double-negative (DN) cells, and splenic CD4+ T cells from tolerant mice displayed a greater suppression than lymph node CD4+ T cells. Cell contact was required for efficient suppression, and known inhibitory cytokines such as IL-4, IL-10, and transforming growth factor β were not involved. Suppressor T cells inhibited IL-2 production by naive CD4+ T cells, and the addition of exogenous IL-2 diminished the suppressed activity while having little activity on tolerant T cells. Suppression was abolished by the elimination of CD25+ T cells in the tolerant CD4+ T cell subset. CD25+CD4+ T cells suppressed the proliferative response of the residual fraction of the nonanergic population, namely, 6C10+CD4+ T cells still present in the tolerant mice. However, 6C10−CD4+ T cells still had reduced reactivity to Mls-1a even after CD25+CD4+ T cells were removed and exogenous IL-2 was added. Suppressor cells appear to affect only residual nonanergic cells in situ, thereby facilitating the maintenance of the unresponsive state in vivo. These data provide a framework for understanding suppressor T cells and explain the difficulties and variables in defining their activity in other systems, because suppressor T cells apparently control only a small population of nonanergic cells in the periphery and may be viewed as a homeostatic mechanism.

Unique molecular surface features of in vivo tolerized T cells

Differential expression of surface markers can frequently be used to distinguish functional subsets of T cells, yet a surface phenotype unique to T cells induced into an anergic state has not been described. Here, we report that CD4 T cells rendered anergic in vivo by superantigen can be identified by loss of the 6C10 T cell marker. Inoculation of Vβ8.1 T cell antigen receptor (TCR) transgenic mice with a Vβ8.1-reactive minor lymphocyte-stimulating superantigen (Mls-1a) induces tolerance to Mls-1a by clonal anergy. CD4 lymph node T cells from Mls-1a inoculated transgenic mice enriched for the 6C10− phenotype neither proliferate nor produce interleukin-2 upon TCR engagement, whereas 6C10+ CD4 T cells retain responsiveness. Analysis of T cell memory markers demonstrate that 6C10− T cells remain 3G11hi but express heterogeneous levels of CD45RB, CD62L, CD44, and the CD69 early activation marker, suggesting that T cells at various degrees of activation can be functionally anergic. These studies demonstrate that anergic T cells can be purified based on 6C10 expression permitting examination of issues concerning biochemical and biological features specific to T cell anergy.

Type 2 diabetes: Evidence for linkage on chromosome 20 in 716 Finnish affected sib pairs

We are conducting a genome scan at an average resolution of 10 centimorgans (cM) for type 2 diabetes susceptibility genes in 716 affected sib pairs from 477 Finnish families. To date, our best evidence for linkage is on chromosome 20 with potentially separable peaks located on both the long and short arms. The unweighted multipoint maximum logarithm of odds score (MLS) was 3.08 on 20p (location, x̂ = 19.5 cM) under an additive model, whereas the weighted MLS was 2.06 on 20q (x̂ = 57 cM, recurrence risk, λ̂s = 1.25, P = 0.009). Weighted logarithm of odds scores of 2.00 (x̂ = 69.5 cM, P = 0.010) and 1.92 (x̂ = 18.5 cM, P = 0.013) were also observed. Ordered subset analyses based on sibships with extreme mean values of diabetes-related quantitative traits yielded sets of families who contributed disproportionately to the peaks. Two-hour glucose levels in offspring of diabetic individuals gave a MLS of 2.12 (P = 0.0018) at 9.5 cM. Evidence from this and other studies suggests at least two diabetes-susceptibility genes on chromosome 20. We have also screened the gene for maturity-onset diabetes of the young 1, hepatic nuclear factor 4-a (HNF-4α) in 64 affected sibships with evidence for high chromosomal sharing at its location on chromosome 20q. We found no evidence that sequence changes in this gene accounted for the linkage results we observed.

Aod1, the immunoregulatory locus controlling abrogation of tolerance in neonatal thymectomy-induced autoimmune ovarian dysgenesis, maps to mouse chromosome 16.

Mice thymectomized at three days of age (D3Tx) develop during adulthood a variety of organ-specific autoimmune diseases, including autoimmune ovarian dysgenesis (AOD). The phenotypic spectrum of AOD is characterized by the development of anti-ovarian autoantibodies, oophoritis, and atrophy. The D3Tx model of AOD is unique in that disease induction depends exclusively on perturbation of the normal developing immune system, is T-cell-mediated, and is strain specific. For example, D3Tx A/J mice are highly susceptible to AOD, whereas C57BL/6J mice are resistant. After D3Tx, self ovarian antigens, expressed at physiological levels, trigger an autoimmune response capable of eliciting disease. The D3Tx model provides, therefore, the opportunity to focus on the mechanisms of self-tolerance that are relevant to disease pathogenesis. Previous studies indicate that the principal mechanisms involved in AOD susceptibility are genetically controlled and govern developmental processes associated with the induction and maintenance of peripheral tolerance. We report here the mapping of the Aod1 locus to mouse chromosome 16 within a region encoding several loci of immunologic relevance, including scid, Igl1, VpreB, Igll, Igl1r, Mtv6 (Mls-3), Ly-7, Ifnar, and Ifgt.