Prolonged Graft Survival in Older Recipient Mice Is Determined by Impaired Effector T-Cell but Intact Regulatory T-Cell Responses

Elderly organ transplant recipients represent a fast growing segment of patients on the waiting list. We examined age-dependent CD4+ T-cell functions in a wild-type (WT) and a transgenic mouse transplant model and analyzed the suppressive function of old regulatory T-cells. We found that splenocytes of naïve old B6 mice contained significantly higher frequencies of T-cells with an effector/memory phenotype (CD4+CD44highCD62Llow). However, in-vitro proliferation (MLR) and IFNγ-production (ELISPOT) were markedly reduced with increasing age. Likewise, skin graft rejection was significantly delayed in older recipients and fewer graft infiltrating CD4+T-cells were observed. Old CD4+ T-cells demonstrated a significant impaired responsiveness as indicated by diminished proliferation and activation. In contrast, old alloantigen-specific CD4+CD25+FoxP3+ T-cells demonstrated a dose-dependent well-preserved suppressor function. Next, we examined characteristics of 18-month old alloreactive T-cells in a transgenic adoptive transfer model. Adoptively transferred old T-cells proliferated significantly less in response to antigen. Skin graft rejection was significantly delayed in older recipients, and graft infiltrating cells were reduced. In summary, advanced recipient age was associated with delayed acute rejection and impaired CD4+ T-cell function and proliferation while CD4+CD25+FoxP3+ T-cells (Tregs) showed a well-preserved function

Recycling and Delivery of Homogeneous Fluorous Rhodium Catalysts Using Poly(tetrafluoro­ethylene): “Catalyst-on-a-Tape”

The red–orange fluorous rhodium­(I) complexes ClRh­(P­((CH₂)_<i>m</i>R_f<i>n</i>)₃)₃ (<i>m</i>/<i>n</i> = 2/6 (<b>1a</b>), 2/8, 3/6, 3/10; R_f<i>n</i> = (CF₂)_<i>n</i>−1CF₃) are essentially insoluble in organic solvents at 20 °C but have measurable solubilities in dibutyl ether at 55–65 °C. Under these conditions, they are effective catalyst precursors for the hydrosilylation of cyclohexanone by PhMe₂SiH. Upon cooling, the catalyst rest states precipitate, giving colorless solutions of C₆H₁₁OSiPhMe₂. When this sequence is conducted in the presence of poly­(tetrafluoro­ethylene) (PTFE; Teflon) tape, the catalysts precipitate onto the tape but desorb when used in subsequent cycles. The catalyst precursors can also be precoated onto the tape, allowing quantities to be delivered by length instead of mass. Rate measurements (<b>1a</b>) show an induction period in the first cycle, excellent retention of activity in the second and third cycles, and significant activity loss in the fourth. Rhodium leaching is 0.57% and 5.3% for the first two cycles (atomic absorption spectroscopy inductively coupled plasma analysis); (CF₂)₅CF₃ leaching is 11.4% over the first three cycles (¹⁹F NMR). Reactions with added mercury show that metallic rhodium is not responsible for catalysis. Identical protocols are applied to 2-octanone, acetophenone, and benzophenone, albeit with some activity loss in the third cycle. Other forms of PTFE can be similarly employed (e.g., Gore-Tex membrane). However, fluorous/organic liquid/liquid biphase conditions can give better retention of catalyst activity. Nonetheless, the diverse morphologies of PTFE that are commercially available suggest avenues for further optimization

Untersuchung neuer Ringfluessigkeiten fuer den Fluessigkeitsringverdichter einer Hochtemperatur-Kompressions-Waermepumpe mit dem Arbeitsmedium Wasser Schlussbericht

SIGLEAvailable from TIB Hannover: F01B810 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Bundesstiftung Umwelt, Osnabrueck (Germany)DEGerman