Decoupled CuO_2 and RuO_2 layers in superconducting and magnetically ordered RuSr_2GdCu_2O_8

Comprehensive measurements of dc and ac susceptibility, dc resistance, magnetoresistance, Hall resistivity, and microwave absorption and dispersion in fields up to 8 T have been carried out on RuSr_2GdCu_2O_8 with the aim to establish the properties of RuO_2 and CuO_2 planes. At ~130 K, where the magnetic order develops in the RuO_2 planes, one observes a change in the slope of dc resistance, change in the sign of magnetoresistance, and the appearance of an extraordinary Hall effect. These features indicate that the RuO_2 planes are conducting. A detailed analysis of the ac susceptibility and microwave data on both, ceramic and powder samples show that the penetration depth remains frequency dependent and larger than the London penetration depth even at low temperatures. We conclude that the conductivity in the RuO_2 planes remains normal even when superconducting order is developed in the CuO_2 planes below \~45 K. Thus, experimental evidence is provided in support of theoretical models which base the coexistence of superconductivity and magnetic order on decoupled CuO_2 and RuO_2 planes.Comment: 11 pages, 11 figures, submitted to PR

HLA and KIR genetic association and NK cells in anti-NMDAR encephalitis

Introduction: Genetic predisposition to autoimmune encephalitis with antibodies against N-methyl-D-aspartate receptor (NMDAR) is poorly understood. Given the diversity of associated environmental factors (tumors, infections), we hypothesized that human leukocyte antigen (HLA) and killer-cell immunoglobulin-like receptors (KIR), two extremely polymorphic gene complexes key to the immune system, might be relevant for the genetic predisposition to anti-NMDAR encephalitis. Notably, KIR are chiefly expressed by Natural Killer (NK) cells, recognize distinct HLA class I allotypes and play a major role in anti-tumor and anti-infection responses. Methods: We conducted a Genome Wide Association Study (GWAS) with subsequent control-matching using Principal Component Analysis (PCA) and HLA imputation, in a multi-ethnic cohort of anti-NMDAR encephalitis (n=479); KIR and HLA were further sequenced in a large subsample (n=323). PCA-controlled logistic regression was then conducted for carrier frequencies (HLA and KIR) and copy number variation (KIR). HLA-KIR interaction associations were also modeled. Additionally, single cell sequencing was conducted in peripheral blood mononuclear cells from 16 cases and 16 controls, NK cells were sorted and phenotyped. Results: Anti-NMDAR encephalitis showed a weak HLA association with DRB1*01:01~DQA1*01:01~DQB1*05:01 (OR=1.57, 1.51, 1.45; respectively), and DRB1*11:01 (OR=1.60); these effects were stronger in European descendants and in patients without an underlying ovarian teratoma. More interestingly, we found increased copy number variation of KIR2DL5B (OR=1.72), principally due to an overrepresentation of KIR2DL5B*00201. Further, we identified two allele associations in framework genes, KIR2DL4*00103 (25.4% vs. 12.5% in controls, OR=1.98) and KIR3DL3*00302 (5.3% vs. 1.3%, OR=4.44). Notably, the ligands of these KIR2DL4 and KIR3DL3, respectively, HLA-G and HHLA2, are known to act as immune checkpoint with immunosuppressive functions. However, we did not find differences in specific KIR-HLA ligand interactions or HLA-G polymorphisms between cases and controls. Similarly, gene expression of CD56dim or CD56bright NK cells did not differ between cases and controls. Discussion: Our observations for the first time suggest that the HLA-KIR axis might be involved in anti-NMDAR encephalitis. While the genetic risk conferred by the identified polymorphisms appears small, a role of this axis in the pathophysiology of this disease appears highly plausible and should be analyzed in future studies