Showing papers by "Kanneboyina Nagaraju published in 2002"

Histidyl–tRNA Synthetase and Asparaginyl–tRNA Synthetase, Autoantigens in Myositis, Activate Chemokine Receptors on T Lymphocytes and Immature Dendritic Cells

Abstract: Autoantibodies to histidyl–tRNA synthetase (HisRS) or to alanyl–, asparaginyl–, glycyl–, isoleucyl–, or threonyl–tRNA synthetase occur in ∼25% of patients with polymyositis or dermatomyositis. We tested the ability of several aminoacyl–tRNA synthetases to induce leukocyte migration. HisRS induced CD4+ and CD8+ lymphocytes, interleukin (IL)-2–activated monocytes, and immature dendritic cells (iDCs) to migrate, but not neutrophils, mature DCs, or unstimulated monocytes. An NH2-terminal domain, 1–48 HisRS, was chemotactic for lymphocytes and activated monocytes, whereas a deletion mutant, HisRS-M, was inactive. HisRS selectively activated CC chemokine receptor (CCR)5-transfected HEK-293 cells, inducing migration by interacting with extracellular domain three. Furthermore, monoclonal anti-CCR5 blocked HisRS-induced chemotaxis and conversely, HisRS blocked anti-CCR5 binding. Asparaginyl–tRNA synthetase induced migration of lymphocytes, activated monocytes, iDCs, and CCR3-transfected HEK-293 cells. Seryl–tRNA synthetase induced migration of CCR3-transfected cells but not iDCs. Nonautoantigenic aspartyl–tRNA and lysyl–tRNA synthetases were not chemotactic. Thus, autoantigenic aminoacyl–tRNA synthetases, perhaps liberated from damaged muscle cells, may perpetuate the development of myositis by recruiting mononuclear cells that induce innate and adaptive immune responses. Therefore, the selection of a self-molecule as a target for an autoantibody response may be a consequence of the proinflammatory properties of the molecule itself.

Sources of variability and effect of experimental approach on expression profiling data interpretation

Abstract: We provide a systematic study of the sources of variability in expression profiling data using 56 RNAs isolated from human muscle biopsies (34 Affymetrix MuscleChip arrays), and 36 murine cell culture and tissue RNAs (42 Affymetrix U74Av2 arrays) We studied muscle biopsies from 28 human subjects as well as murine myogenic cell cultures, muscle, and spleens Human MuscleChip arrays (4,601 probe sets) and murine U74Av2 Affymetrix microarrays were used for expression profiling RNAs were profiled both singly, and as mixed groups Variables studied included tissue heterogeneity, cRNA probe production, patient diagnosis, and GeneChip hybridizations We found that the greatest source of variability was often different regions of the same patient muscle biopsy, reflecting variation in cell type content even in a relatively homogeneous tissue such as muscle Inter-patient variation was also very high (SNP noise) Experimental variation (RNA, cDNA, cRNA, or GeneChip) was minor Pre-profile mixing of patient cRNA samples effectively normalized both intra- and inter-patient sources of variation, while retaining a high degree of specificity of the individual profiles (86% of statistically significant differences detected by absolute analysis; and 85% by a 4-pairwise comparison survival method) Using unsupervised cluster analysis and correlation coefficients of 92 RNA samples on 76 oligonucleotide microarrays, we found that experimental error was not a significant source of unwanted variability in expression profiling experiments Major sources of variability were from use of small tissue biopsies, particularly in humans where there is substantial inter-patient variability (SNP noise)

Animal models of myositis

Abstract: Current animal models of human myositis include spontaneous, induced, and transgenic models. Although it is clear that none of these models possesses all the features of the human diseases, they may provide insight into the pathophysiologic mechanisms, and possibly the therapy, of inflammatory muscle disease. Because the human IIMs are phenotypically heterogeneous, but may be divided into more homogeneous subgroups based upon clinical or serologic features, it is possible that different pathogeneses are involved in different subgroups. It is unlikely that any single model would reproduce all features of the human disease. It may be possible, however, to gain insight into some subgroups of the human disease if certain animal models faithfully reproduce one or more subtypes or aspects of the IIMs. Because immunogenetic risk factors, and exposure to certain environmental agents important in triggering myositis in genetically susceptible persons, may be necessary components for human disease induction, transgenic approaches to humanizing murine immune systems and a better understanding of environmental risk factors will be productive avenues for future research. Additional investigations into the molecular basis of the human myositis syndromes and the pathogenesis of the spontaneous, induced, and transgenic animal models should ultimately allow for better understanding and therapy of these diseases.