RESUMO
It is hypothesized that autoimmune diseases manifest when tolerance to self-Ags fails. One possible mechanism to break tolerance is presentation of self-Ag in an altered form. Most Ags are presented by APCs via the traditional presentation pathway that includes "epitope editing" by intracellular HLA-DM, a molecule that selects for stable MHC-peptide complexes. We were interested in testing the hypothesis that autoreactive MHC-peptide complexes may reach the cell surface by an alternate pathway without being edited by HLA-DM. We selected a cartilage autoantigen human cartilage glycoprotein 39 to which T cell responses are observed in rheumatoid arthritis (RA) patients and some DR(*)04 healthy subjects. RA is genetically associated with certain DRB1 alleles, including DRB1(*)0401 but closely related allele DRB1(*)0402 is either neutral or mildly protective with respect to RA. We generated human B lymphoblastoid cell line cells expressing DR(*)0401 or DR(*)0402 in the presence or absence of intracellular HLA-DM and assessed their ability to present a candidate autoantigen, human cartilage glycoprotein 39. Our results show that the presence of intracellular HLA-DM is critical for presentation of this autoantigen to CD4(+) T cell hybridomas generated from DR(*)04-transgenic mice. Presentation of an autoantigen by the traditional HLA-DM-dependent pathway has implications for Ag presentation events in RA.
Assuntos
Apresentação de Antígeno , Autoantígenos/metabolismo , Linfócitos B/metabolismo , Epitopos de Linfócito B/metabolismo , Glicoproteínas/imunologia , Antígenos HLA-D/fisiologia , Adipocinas , Animais , Apresentação de Antígeno/genética , Linfócitos B/imunologia , Cartilagem Articular/imunologia , Cartilagem Articular/metabolismo , Linhagem Celular Transformada , Proteína 1 Semelhante à Quitinase-3 , Glicoproteínas/metabolismo , Antígenos HLA-D/biossíntese , Antígenos HLA-D/genética , Antígenos HLA-DR/genética , Cadeias HLA-DRB1 , Humanos , Hibridomas , Lectinas , Camundongos , Camundongos Transgênicos , Fragmentos de Peptídeos/imunologia , Fragmentos de Peptídeos/metabolismo , Transdução de Sinais/genética , Transdução de Sinais/imunologia , Linfócitos T/imunologia , Linfócitos T/metabolismo , TransfecçãoRESUMO
The histochemical and enzyme cytochemical effects of Toxaphene were investigated using isolated hepatocytes in suspension culture from laboratory-bred juvenile, female yellowtail flounder (Pleuronectes ferrugineus). Hepatocytes were kept in suspension culture for 4 days and exposed for 3 days to a control medium, to a medium with hexane (the solvent of Toxaphene), or to a medium with Toxaphene in two different concentrations (1 and 10 mocrog/ml). Subsequently, the cultivated cells were examined histochemically (Sudan black B, oil red O, Schmorl's reaction) and enzyme cytochemically (acid phosphatase, NADPH-ferrohemoprotein reductase). Toxaphene decreased the viability of the isolated cells significantly, as compared to the control suspensions. Toxaphene also increased the storage of total and neutral lipids (as demonstrated by Sudan black B and oil red O, respectively) in a dose-dependent manner. In addition, Toxaphene increased the enzymatic activity of acid phosphatase, and increased the storage of lipofuscin pigment (as demonstrated by the Schmorl's reaction) within the hepatocytes, suggesting an increase in the number and/or size of the lysosomes. Hexane did not have a significant toxic effect on the isolated hepatocytes. It is concluded that Toxaphene is potentially toxic to fish in a marine environment and that this in vitro system may provide a model for assessing the direct effect of various toxicants on fish hepatocytes.