Detection, epitope-mapping and function of anti-Fas autoantibody in patients with silicosis.

Dysregulation of apoptosis through the Fas-Fas ligand pathway is associated with the onset of autoimmune disease. Since autoantibodies directed against unknown antigens are present in the sera of these patients, sera samples were examined for the presence of autoantibodies directed against the Fas molecule. Using Western blotting and a ProteinChip analysis, autoantibodies against Fas were detected in patients with silicosis, systemic lupus erythematosus (SLE) and systemic sclerosis (SSc), and weakly detected in healthy individuals. Using epitope mapping employing 12-amino-acid polypeptides with the SPOTs system, a minimum of four epitopes and a maximum of 10 epitopes were found. Several amino acid residues involved in binding FasL, such as C66, R87, L90, E93 and H126, were presented within the epitopes. Serum containing a large amount of anti-Fas autoantibody from silicosis patients inhibited the growth of a Fas-expressing human cell line, but did not inhibit the growth of a low Fas-expresser nor a Fas-expresser in which the Fas gene had been silenced by small interference RNA. All epitopes in the intracellular region of Fas were located in the death domain. The possible roles of anti-Fas autoantibody detected in healthy volunteers and patients with silicosis or autoimmune diseases are discussed here.

Induction of CD69 antigen expression in peripheral blood mononuclear cells on exposure to silica, but not by asbestos/chrysotile-A.

While cases of silicosis are often complicated by various autoimmune disorders, patients with asbestosis develop malignant tumors such as lung cancer and malignant mesothelioma. These differences may derive from different biological effects, particularly on immunological cells, of silica and asbestos. To find differences between silica and asbestos, the early activation antigen, CD69, on T cells was examined because dysregulated and continuous activation of T cells may promote the survival of self-recognizing T cells. After cultivation of peripheral blood mononuclear cells with or without silica or chrysotile-A, an asbestos, only silica induced CD69 expression on the lymphocytes. This induction of CD69 expression was mediated by protein kinase C activation. In addition, cell-cell contact mediated by HLA-DR was more important than soluble factors secreted from silica-phagocytosed cells such as IL-1beta, IL-6, and IL-8, even though IL-6 and IL-8 were produced during the culture of PBMCs with silica and chrysotile-A. It should be examined how these activated, CD69-expressing lymphocytes affect other immune systems as well as alter themselves in terms of cytokine production and cell-cell interaction, leading to autoimmune disorders in silicosis patients.

[Dysregulation of Fas and related molecules in silicosis patients].

Silicosis patients not only suffer from respiratory disorders but also from autoimmune diseases. To clarify the mechanisms involved in the occurrence of the dysregulation of autoimmunity found in silicosis patients, we have been focusing on investigation of the Fas and Fas-related molecules in the Fas-mediated apoptotic pathway, since Fas is one of the most important molecules regulating autoimmunity in mainly T cells. Our findings showed that silicosis patients exhibited elevated serum soluble Fas levels, increased relative expression of soluble Fas and DcR 3 genes in peripheral blood mononuclear cells, other highly detectable variant messages of Fas transcripts, relatively decreased expression of several physiological inhibitors (Sentrin, I-Fline, ICAD/DFF45, and survivin), and dominancy of lower membrane Fas expressers in lymphocytes when compared with healthy volunteers. These parameters also constitute immunological factors with serum immunogulobulin G and the titer of anti-nuclear autoantibodies. In addition, anti-caspase 8 autoantibody and anti-Fas autoantibody were also detected in the serum from silicosis patients, and a functional assay showed that anti-Fas antibody stimulated Fas-mediated apoptosis. Taken together, we hypothesize that there are two subpopulations of silicosis lymphocytes. One is a long-term survival fraction including a self-recognizing fraction showing lower membrane Fas and inhibition of Fas/Fas ligand bindings in the extracellular region. The other is a fraction exhibiting apoptosis caused by silica/silicates, recruiting from bone marrow, showing higher membrane Fas and sensitive to anti-Fas autoantibody. Further investigations should be performed to confirm the effects of silica/silicates on the human immune system.

Effects of genetic and nutritional factors on bone mineral density in young adults.

To estimate the genetic and dietary factors influencing bone mineral density (BMD) in young adults, a total of 53 healthy volunteers (HV) (age 20.89+/-1.34), from whom informed consent was obtained, answered a questionnaire on dietary factors and had DNA from peripheral blood mononuclear cells analyzed for single nucleotide polymorphisms (SNPs) for vitamin (Vit) D receptor (VDR), estrogen receptor alpha (ERalpha), interleukin 1 receptor antagonist (IL1RA), and apolipoprotein E (ApoE) genes. Daily intakes of Vit C, fiber, soybean and related foods, and green and yellow vegetables showed a correlation with % BMD. In addition, Vit B2 as well as Vit C, and vegetables were identified as important factors for BMD by Stepwise regression analysis. Among the SNPs analyzed, the B+ type of the VDR gene tended to be associated with a lower BMD, and pp type of the ER gene digested by the PvuII enzyme in females indicated a significantly lower BMD than that in males. In addition, these SNPs were also identified by factor analysis to be associated with BMD. These results suggested that a complex array of genetic factors, such as two or more SNPs or SNPs and gender, may be important to BMD.