(BALB/c x C57BL/6)F1 mice are tolerant to undetectable mixed haplotype A beta dA alpha b and mixed isotype A beta dE alpha d self class II molecules

CD4+ T-cell responses to self-peptide--MHC

Interactions between the T-cell receptor (TCR) and self-peptide-MHC (spMHC) have been hypothesized to modulate T-cell reactivity in the periphery. Recent studies examining CD4+ T-cell responses to spMHC class II describe apparently contradictory findings and arrive at opposite conclusions. One explanation for these seemingly disparate results could be the use of mice that were assumed to be MHC class II null but might express some uncommon MHC class II heterodimers.

Resistance to cyclophosphamide-induced diabetes in transgenic NOD mice expressing I-Ak

Transgenic expression of the MHC (major histocompatibility complex) class II I-Ak molecule was previously shown to effectively reduce the incidence of insulitis in non-obese diabetic (NOD) mice at the age of 20 weeks. We have further characterized the expression and function of the I-Ak molecule and examined its effects on the incidence of diabetes in NOD mice. The newly expressed I-Ak molecule was recognized as an alloantigen by the T lymphocytes of normal NOD mice as shown by mixed lymphocyte reaction (MLR). The levels of endogenous I-Ag7 expression on peripheral blood lymphocytes were not affected by the transgene expression. Transgenic NOD mice were completely resistant to spontaneous diabetes, but the treatment by cyclophosphamide, which effectively induces diabetes in normal NOD mice, caused diabetes, although at a much lower incidence than that of normal NOD mice. On the basis of these findings, we discuss the role of I-Ak in the prevention of diabetes in NOD mice.

Complete prevention of diabetes in transgenic NOD mice expressing I-E molecules

Previously, we showed that transgenic expression of the MHC (major histocompatibility complex) class II I-E molecules prevented insulitis in non-obese diabetic (NOD) mice at the age of 19 weeks. To rule out the possibility that the I-E expression merely delays the onset of insulitis, we have further characterized the expression and function of the I-E molecule expressed in transgenic NOD mice and confirmed our previous observations. Northern blot analysis showed that the transgenic E alpha d gene was expressed in a pattern similar to the endogenous E alpha d gene in BALB/c mice. The newly expressed I-E molecules were recognized as an alloantigen by the T lymphocytes of normal NOD mice as shown by mixed lymphocyte reaction (MLR). Transgenic NOD mice were resistant to the treatment by cyclophosphamide, which effectively induces diabetes in normal NOD mice, and did not develop diabetes up to 40 weeks of age. On the basis of these findings, we discuss the role of I-E molecules in the prevention of diabetes in NOD mice.