SummaryAccumulation of plasma cells in the synovium is one of the diagnostic hallmarks in the histopathological manifestations of rheumatoid arthritis (RA). This seems to be prominent even prior to significant B cell infiltration and/or formation of lymphoid follicles in the synovium. To clarify the mechanism of early plasma cell accumulation, we examined in situ expression of chemokines and their receptors using synovial targeting biopsy specimens, which were obtained under arthroscopy from early RA patients. By immunohistochemical staining, plasma cells were found to express a chemokine receptor CXCR3, while synovial fibroblasts in the synovial sublining regions expressed its ligand, Mig/CXCL9. By reverse transcription-polymerase chain reaction (RT-PCR), using targeted lesions of synovial tissues obtained by laser capture microdissection, expression levels of Mig/CXCL9 in the synovial sublining regions were remarkably high and were likely to be associated with interferon (IFN)-g g g g expression. Furthermore, cultured synovial fibroblasts were confirmed to produce Mig/CXCL9 upon stimulation with IFN-g g g g . Our results indicate that in the early stage of RA, plasma cells expressing CXCR3 may be recruited directly from the circulation into the synovial sublining regions by its ligand, Mig/CXCL9, produced by synovial fibroblasts.

The results indicate that sialadenitis in MRL/lpr mice is under the control of polygenic inheritance, possibly involving allelic polymorphism.

Objective. To clarify the mode of inheritance and the genome origins of arthritis in a lupus-prone strain of mice, MRL/MpJ, bearing a Fas deletion mutant gene, lpr (MRL/lpr).Methods. Using non-lupus-prone strains of mice, C3H/HeJ-lpr/lpr (C3H/lpr), (MRL/lpr ؋ C3H/lpr)F 1 intercross and MRL/lpr ؋ (MRL/lpr ؋ C3H/lpr)F 1 backcross mice were prepared. Arthritis in individual mice was analyzed by histopathologic grading, and the genomic DNA of the backcross mice was examined by simple sequence-length polymorphism analysis to determine the polymorphic microsatellite markers highly associated with arthritis.Results. Arthritis-susceptibility loci with significant linkage were mapped between D15Mit111 and D15Mit18 (map position 17.8-18.7 cM) on chromosome 15 and between D19Mit112 and D19Mit72 (map position 43.0-55.0) on chromosome 19 (logarithm of odds scores 3.5 and 4.3, respectively). Three other loci, one mapped to each of chromosomes 1, 2, and 7, showed suggestive linkage. Loci homozygous for MRL alleles on chromosomes 1 and 19 enhanced arthritis in both sexes, whereas other loci on chromosomes 2 and 15 selectively affected males. A locus homozygous for MRL alleles on chromosome 7 inhibited arthritis in both sexes. Three of these loci were found to originate from an LG/J strain and 1 from an AKR/J strain. Some combinations of these loci showed an additive effect in a hierarchical manner on the development of arthritis.Conclusion. Arthritis in MRL/lpr mice is a complex pathologic manifestation resulting from the cumulative effect of multiple gene loci with an allelic combination derived from the original inbred strains.

An MRL strain of mice bearing a Fas-deletion mutant gene, lpr, MRL/MpJ-lpr/lpr (MRL/lpr) develops collagen disease involving vasculitis, glomerulonephritis, arthritis and sialoadenitis, each of which has been studied as a model for polyarteritis, lupus nephritis, rheumatoid arthritis and Sjögren's syndrome, respectively. Development of such lesions seems dependent on host genetic background since the congenic C3H/HeJ-lpr/lpr (C3H/lpr) mice rarely develop them. To identify the gene loci affecting each lesion, a genetic dissection of these complex pathological manifestations was carried out. First, histopathological features in MRL/lpr, C3H/lpr, (MRL/lpr x C3H/lpr) F1 intercross, and MRL/lpr x (MRL/lpr x C3H/lpr) F1 backcross mice were analyzed. Genomic DNA of the backcross mice were subjected to association studies by Chi-squared analysis for determining which polymorphic microsatellite locus occurs at higher frequency among affected compared to unaffected individuals for each lesion. As a result, gene loci recessively associated with each lesion were mapped on different chromosomal positions. We concluded that each of these lesions in MRL/lpr mice is under the control of a different set of genes, suggesting that the complex pathological manifestations of collagen disease result from polygenic inheritance.

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