RESUMO
Mixed connective tissue disease (MCTD) is a systemic autoimmune disease with significant morbidity and premature mortality of unknown pathogenesis. In the present study, we characterized U1-70-kDa small nuclear ribonucleoprotein (70-kDa) autoantigen-specific T cells in a new murine model of MCTD. These studies defined 70-kDa-reactive T cell Ag fine specificities and TCR gene usage in this model. Similar to patients with MCTD, CD4(+) T cells can be readily identified from 70-kDa/U1-RNA-immunized HLA-DR4-transgenic mice. Using both freshly isolated CD4(+) T cells from spleen and lung, and T cell lines, we found that the majority of these T cells were directed against antigenic peptides residing within the RNA-binding domain of 70 kDa. We also found that TCR-beta (TRB) V usage was highly restricted among 70-kDa-reactive T cells, which selectively used TRBV subgroups 1, 2, 6, 8.1, 8.2, and 8.3, and that the TRB CDR3 had conserved sequence motifs which were shared across different TRBV subgroups. Finally, we found that the TRBV and CDR3 regions used by both murine and human 70-kDa-specific CD4(+) T cells were homologous. Thus, T cell recognition of the 70-kDa autoantigen by HLA-DR4-transgenic mice is focused on a limited number of T cell epitopes residing primarily within the RBD of the molecule, using a restricted number of TRBV and CDR3 motifs that are homologous to T cells isolated from MCTD patients.
Assuntos
Autoantígenos/metabolismo , Linfócitos T CD4-Positivos/imunologia , Epitopos de Linfócito T/metabolismo , Rearranjo Gênico da Cadeia beta dos Receptores de Antígenos dos Linfócitos T , Antígeno HLA-DR4/genética , Doença Mista do Tecido Conjuntivo/imunologia , Ribonucleoproteína Nuclear Pequena U1/imunologia , Ribonucleoproteínas Nucleares Pequenas/imunologia , Sequência de Aminoácidos , Animais , Autoanticorpos/biossíntese , Autoantígenos/administração & dosagem , Autoantígenos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD4-Positivos/patologia , Linhagem Celular , Movimento Celular/genética , Movimento Celular/imunologia , Modelos Animais de Doenças , Epitopos de Linfócito T/genética , Epitopos de Linfócito T/imunologia , Antígenos HLA-A/administração & dosagem , Antígenos HLA-A/genética , Antígenos HLA-A/imunologia , Antígenos HLA-DR/administração & dosagem , Antígenos HLA-DR/genética , Antígenos HLA-DR/imunologia , Cadeias HLA-DRB1 , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Doença Mista do Tecido Conjuntivo/genética , Doença Mista do Tecido Conjuntivo/patologia , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Ribonucleoproteína Nuclear Pequena U1/administração & dosagem , Ribonucleoproteína Nuclear Pequena U1/metabolismo , Ribonucleoproteínas Nucleares Pequenas/administração & dosagem , Ribonucleoproteínas Nucleares Pequenas/metabolismoRESUMO
The pathologic hallmarks of diabetic nephropathy are excess mesangial extracellular matrix (ECM) and mesangial cell proliferation. We previously showed that mesangial cell phenotypic changes play an important role in the pathogenesis of diabetic nephropathy. We concluded that phenotypic changes were present in bone marrow (BM)-derived mesangial cell progenitors, as transplantation of BM from db/db mice, a model of type 2 diabetic nephropathy, transferred the db genotype and a nephropathy phenotype to naive B6 mice recipients. The recipients did not develop diabetes; however, they did develop albuminuria and glomerular lesions mirroring those in the donors (i.e., glomerular hypertrophy, increased ECM, and increased cell number with cell proliferation). We found that matrix metalloproteinase 2 (MMP-2) facilitated invasion of the mesangial cells into ECM and proliferation in vitro. Thus, increased MMP-2 activity in db/db mesangial cell progenitors may partially explain increased mesangial cell repopulation and proliferation in B6 recipients of db/db BM. In summary, BM-derived mesangial cell progenitors may play a crucial role in the development and progression of ECM accumulation and mesangial cell proliferation in this model of diabetic nephropathy in type 2 diabetes.