OBJECTIVEThe autoimmune destruction of β-cells in type 1 diabetes results in a loss of insulin production and glucose homeostasis. As such, an immense interest exists for the development of therapies capable of attenuating this destructive process through restoration of proper immune recognition. Therefore, we investigated the ability of the immune-depleting agent antithymocyte globulin (ATG), as well as the mobilization agent granulocyte colony–stimulating factor (GCSF), to reverse overt hyperglycemia in the nonobese diabetic (NOD) mouse model of type 1 diabetes.RESEARCH DESIGN AND METHODSEffects of each therapy were tested in pre-diabetic and diabetic female NOD mice using measurements of glycemia, regulatory T-cell (CD4+CD25+Foxp3+) frequency, insulitis, and/or β-cell area.RESULTSHere, we show that combination therapy of murine ATG and GCSF was remarkably effective at reversing new-onset diabetes in NOD mice and more efficacious than either agent alone. This combination also afforded durable reversal from disease (>180 days postonset) in animals having pronounced hyperglycemia (i.e., up to 500 mg/dl). Additionally, glucose control improved over time in mice subject to remission from type 1 diabetes. Mechanistically, this combination therapy resulted in both immunological (increases in CD4-to-CD8 ratios and splenic regulatory T-cell frequencies) and physiological (increase in the pancreatic β-cell area, attenuation of pancreatic inflammation) benefits.CONCLUSIONSIn addition to lending further credence to the notion that combination therapies can enhance efficacy in addressing autoimmune disease, these studies also support the concept for utilizing agents designed for other clinical applications as a means to expedite efforts involving therapeutic translation.

OBJECTIVE-Antilymphocyte serum can reverse overt type 1 diabetes in NOD mice; yet, the therapeutic parameters and immunological mechanisms underlying the ability for this agent to modulate autoimmune responses against ␤-cells are unclear, forming the rationale for this investigation.RESEARCH DESIGN AND METHODS-A form of antilymphocyte serum, rabbit anti-mouse thymocyte globulin (mATG), was utilized in a variety of in vivo and in vitro settings, each for the purpose of defining the physiological, immunological, and metabolic activities of this agent, with particular focus on actions influencing development of type 1 diabetes.RESULTS-We observed that mATG attenuates type 1 diabetes development in an age-dependent fashion, only proving efficacious at disease onset or in the late pre-diabetic phase (12 weeks of age). When provided at 12 weeks of age, mATG reversed pancreatic insulitis, improved metabolic responses to glucose challenge, and rapidly increased frequency of antigen-presenting cells in spleen and pancreatic lymph nodes. Surprisingly, mATG therapy dramatically increased, in an age-dependent fashion, the frequency and the functional activity of CD4 ϩ CD25 ϩ regulatory T-cells. Adoptive transfer/cotransfer studies of type 1 diabetes also support the concept that mATG treatment induces a stable and transferable immunomodulatory repertoire in vivo.CONCLUSIONS-These findings indicate that an induction of immunoregulation, rather than simple lymphocyte depletion, contributes to the therapeutic efficacy of antithymocyte globulin and suggest that time-dependent windows for the ability to delay or reverse type 1 diabetes exist based on the capacity to enhance the functional activity of regulatory T-cells. Diabetes 57: [405][406][407][408][409][410][411][412][413][414] 2008

A series of mutations comprising single and multiple substitutions, deletions, and extensions within the carboxy-terminal domain of the bacteriophage lambda Cro repressor have been constructed. These mutations generally affect the affinity of repressor for specific and nonspecific DNA. Additionally, substitution of the carboxy-terminal alanine with several amino acids capable of hydrogen-bonding interactions leads to improved specific binding affinities. A mutation is also described whereby cysteine links the two Cro monomers by a disulfide bond. As a consequence, a significant improvement in nonspecific binding and a concomitant reduction in specific binding are observed with this mutant. These results provide evidence that the carboxy terminus of Cro repressor is an important DNA binding domain and that a flexible connection between the two repressor monomers is a critical factor in modulating the affinity of wild-type repressor for DNA.

BackgroundATG has been employed to deplete T cells in several immune-mediated conditions. However, whether ATG administration affects naïve and memory T cell differently is largely unknown.The context and purpose of the studyIn this study, we assessed how murine ATG therapy affected T cell subsets in NOD mice, based on their regulatory and naïve or memory phenotype, as well as its influence on antigen-specific immune responses.ResultsPeripheral blood CD4+ and CD8+ T cells post-ATG therapy declined to their lowest levels at day 3, while CD4+ T cells returned to normal levels more rapidly than CD8+ T cells. ATG therapy failed to eliminate antigen-primed T cells. CD4+ T cell responses post-ATG therapy skewed to T helper type 2 (Th2) and possibly IL-10-producing T regulatory type 1 (Tr1) cells. Intriguingly, Foxp3+ regulatory T cells (Tregs) were less sensitive to ATG depletion and remained at higher levels following in vivo recovery compared to controls. Of note, the frequency of Foxp3+ Tregs with memory T cell phenotype was significantly increased in ATG-treated animals.ConclusionATG therapy may modulate antigen-specific immune responses through inducing memory-like regulatory T cells as well as other protective T cells such as Th2 and IL-10-producing Tr1 cells.