Vav1 regulates the migration and adhesion of dendritic cells.

Dendritic cells (DCs) are the most potent APCs for activating naive T cells, a process facilitated by the ability of immature DCs to mature and home to lymph nodes after encountering an inflammatory stimulus. Proteins involved in cytoskeletal rearrangement play an important role in regulating the adherence and motility of DCs. Vav1, a guanine nucleotide exchange factor for Rho family GTPases, mediates cytoskeletal rearrangement in hematopoietic cells following integrin ligation. We show that Vav1 is not required for the normal maturation of DCs in vitro; however, it is critical for DC binding to fibronectin and regulates the distribution but not the formation of podosomes. We also found that DC Vav1 was an important component of a signaling pathway involving focal adhesion kinase, phospholipase C-gamma2, and ERK1/2 following integrin ligation. Surprisingly, Vav1(-/-) DCs had increased rates of migration in vivo compared with wild-type control DCs. In vitro findings show that the presence of adhesive substrates such as fibronectin resulted in inhibition of migration. However, there was less inhibition in the absence of Vav1. These findings suggest that DC migration is negatively regulated by adhesion and integrin-mediated signaling and that Vav1 has a central role in this process.

Molecular genetic analysis of the Idd4 locus implicates the IFN response in type 1 diabetes susceptibility in nonobese diabetic mice.

High-resolution mapping and identification of the genes responsible for type 1 diabetes (T1D) has proved difficult because of the multigenic etiology and low penetrance of the disease phenotype in linkage studies. Mouse congenic strains have been useful in refining Idd susceptibility loci in the NOD mouse model and providing a framework for identification of genes underlying complex autoimmune syndromes. Previously, we used NOD and a nonobese diabetes-resistant strain to map the susceptibility to T1D to the Idd4 locus on chromosome 11. Here, we report high-resolution mapping of this locus to 1.4 megabases. The NOD Idd4 locus was fully sequenced, permitting a detailed comparison with C57BL/6 and DBA/2J strains, the progenitors of T1D resistance alleles found in the nonobese diabetes-resistant strain. Gene expression arrays and quantitative real-time PCR were used to prioritize Idd4 candidate genes by comparing macrophages/dendritic cells from congenic strains where allelic variation was confined to the Idd4 interval. The differentially expressed genes either were mapped to Idd4 or were components of the IFN response pathway regulated in trans by Idd4. Reflecting central roles of Idd4 genes in Ag presentation, arachidonic acid metabolism and inflammation, phagocytosis, and lymphocyte trafficking, our combined analyses identified Alox15, Alox12e, Psmb6, Pld2, and Cxcl16 as excellent candidate genes for the effects of the Idd4 locus.

Discordant expression of HLA class II-associated co-chaperones and HLA-DRB alleles in cultured fibroblast-like synoviocytes.

Human leukocyte antigen (HLA)-DR-positive synovial fibroblasts are frequently observed in rheumatoid arthritis (RA) and may be implicated in the autoimmune reaction because RA is associated with certain HLA-DRB1* alleles. The question of whether components of the class II antigen presentation pathway and specific DRB alleles are efficiently expressed by synovial fibroblasts is germane to this hypothesis. To address this, cultured fibroblast-like synoviocytes (cFLS) were analyzed for constitutive and interferon (IFN)-gamma-induced expression of specific DRB alleles and class II-associated cochaperones. IFN-gamma induction of invariant chain, DM, and DR molecules was observed in all cFLS, but expression of specific DR allotypes was variable. Interestingly, DM-modulated epitopes on RA-associated DR molecules were either absent or delayed, despite strong DM expression and a paucity of major histocompatibility complex/class II-associated invariant chain peptide complexes. Altered expression of specific peptide-dependent epitopes on RA-associated HLA-DR molecules suggests differences in antigen presentation by cFLS, which may have implications for the immunopathogenesis of RA.