Genetic control of spontaneous arthritis in a four-way advanced intercross line

Quantitative Trait Locus Analysis Implicates CD4⁺/CD44high Memory T Cells in the Pathogenesis of Murine Autoimmune Pancreatitis

The mouse strain MRL/MpJ is prone to spontaneously develop autoimmune pancreatitis (AIP). To elucidate the genetic control towards the development of the phenotype and to characterize contributions of immunocompetent cell types, MRL/MpJ mice were interbred with three additional strains (BXD2/TYJ, NZM2410/J, CAST/EIJ) for four generations in an advanced intercross line. Cellular phenotypes were determined by flow cytometric quantification of splenic leukocytes and complemented by the histopathological evaluation of pancreatic lesions. An Illumina SNP array was used for genotyping. QTL analyses were performed with the R implementation of HAPPY. Out of 41 leukocyte subpopulations (B cells, T cells and dendritic cells), only three were significantly associated with AIP: While CD4⁺/CD44^high memory T cells and CD4⁺/CD69⁺ T helper (Th) cells correlated positively with the disease, the cytotoxic T cell phenotype CD8⁺/CD44^low showed a negative correlation. A QTL for AIP on chromosome 2 overlapped with QTLs for CD4⁺/CD44^high and CD8⁺/CD44^high memory T cells, FoxP3⁺/CD4⁺ and FoxP3⁺/CD8⁺ regulatory T cells (Tregs), and CD8⁺/CD69⁺ cytotoxic T cells. On chromosome 6, overlapping QTLs for AIP and CD4⁺/IL17⁺ Th17 cells and again FoxP3⁺/CD8⁺ Tregs were observed. In conclusion, CD4⁺/CD44^high memory T cells are the only leukocyte subtype that could be linked to AIP both by correlation studies and from observed overlapping QTL. The potential role of this cell type in the pathogenesis of AIP warrants further investigations.

Mouse Models of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic debilitating autoimmune disorder characterized by synovitis that leads to cartilage and bone erosion by invading fibrovascular tissue. Mouse models of RA recapitulate many features of the human disease. Despite the availability of medicines that are highly effective in many patient populations, autoimmune diseases (including RA) remain an area of active biomedical research, and consequently mouse models of RA are still extensively used for mechanistic studies and validation of therapeutic targets. This review aims to integrate morphologic features with model biology and cover the key characteristics of the most commonly used induced and spontaneous mouse models of RA. Induced models emphasized in this review include collagen-induced arthritis and antibody-induced arthritis. Collagen-induced arthritis is an example of an active immunization strategy, whereas antibody- induced arthritis models, such as collagen antibody–induced arthritis and K/BxN antibody transfer arthritis, represent examples of passive immunization strategies. The coverage of spontaneous models in this review is focused on the TNFΔ ARE mouse, in which arthritis results from overexpression of TNF-α, a master proinflammatory cytokine that drives disease in many patients.