CD62L(high) Treg cells with superior immunosuppressive properties accumulate within the CNS during remissions of EAE.

The role of regulatory T cell populations within the CNS in the regulation of CNS-autoimmunity is controversial. We show that during recovery from relapsing remitting experimental autoimmune encephalomyelitis, regulatory T cells accumulate within the CNS that express high levels of CD62L. These CD62L(high) Treg cells express increased amounts of CTLA-4, ICOS and TGF-ß and are more potent than CD62L(low) Treg cells in suppressing proliferation and inducing apoptosis in effector T cells. CD62L(high) Treg cells thus represent a population of Treg cells that display superior immunosuppressive properties and accumulate in the CNS during recovery from CNS-autoimmunity.

Differential modulation of CNS-specific effector and regulatory T cells during tolerance induction by recombinant invariant chains in vivo.

Inflammation within the Central Nervous System (CNS) is largely controlled by the balance between CNS-specific effector and regulatory T lymphocytes. To suppress CNS-inflammation in an antigen-specific manner, CNS-specific effector and regulatory T cells thus have to be differentially regulated. We employed recombinant peptide/MHC class II tetramers to assess CNS-specific effector and regulatory T cells during the specific suppression of myelin proteolipid protein aa139-151 (PLP139-151)-induced experimental autoimmune encephalomyelitis (EAE) by intravenous injection of recombinant invariant chains (Ii) in which the CLIP region has been replaced by the PLP139-151 epitope (Ii-PLP139-151). Injection of Ii-PLP139-151 induced apoptosis in CNS-specific effector T cells. In contrast, the proportion of specific regulatory T cells was increased and these cells expressed larger amounts of molecules that mediate regulatory T cell function including transforming growth factor beta and the inducible costimulator (ICOS). Consequently, regulatory T cells from Ii-treated mice were more potent than regulatory T cells from control-treated animals in suppressing effector T cell proliferation. These data demonstrate that effector T cells and regulatory T cells directed against the same CNS-antigen can be differentially regulated in vivo to suppress CNS-autoimmunity. Recombinant Ii induce apoptosis in CNS-specific effector T cells and provoke qualitative changes in specific regulatory T cells that enhance their immunosuppressive properties.

Synthesis and activity of ruthenium alkylidene complexes coordinated with phosphine and N-heterocyclic carbene ligands.

This paper reports the synthesis and characterization of a variety of ruthenium complexes coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several alkylidene derivatives of the general formula (NHC)(PR(3))(Cl)(2)Ru=CHR', which are highly active olefin metathesis catalysts. Although these catalysts can be prepared adequately by the reaction of bis(phosphine) ruthenium alkylidene precursors with free NHCs, we have developed an alternative route that employs NHC-alcohol or -chloroform adducts as "protected" forms of the NHC ligands. This route is advantageous because NHC adducts are easier to handle than their free carbene counterparts. We also demonstrate that sterically bulky bis(NHC) complexes can be made by reaction of the pyridine-coordinated precursor (NHC)(py)(2)(Cl)(2)Ru=CHPh with free NHCs or NHC adducts. Two crystal structures are presented, one of the mixed bis(NHC) derivative (H(2)IMes)(IMes)(Cl)(2)Ru=CHPh, and the other of (PCy(3))(Cl)(CO)Ru[eta(2)-(CH(2)-C(6)H(2)Me(2))(N(2)C(3)H(4))(C(6)H(2)Me(3))], the product of ortho methyl C-H bond activation. Other side reactions encountered during the synthesis of new ruthenium alkylidene complexes include the formation of hydrido-carbonyl-chloride derivatives in the presence of primary alcohols and the deprotonation of ruthenium vinylcarbene ligands by KOBu(t). We also evaluate the olefin metathesis activity of NHC-coordinated complexes in representative RCM and ROMP reactions.