No abstract

No abstract

No abstract

The restriction enzyme Pstl showed a two-allele restriction fragment length polymorphism (RFLP) marker when DNA polymorphism of the gene G8, a novel major histocompatibility complex (MHC) class III gene, was screened. The gene G8 is located ca. 4 kb centromeric of the heat-shock protein 70 (HSP70) gene cluster. A more detailed mapping indicated that the polymorphic restriction site is actually located in the coding region of the adjacent HSP70-2 gene, where it has been earlier reported to cause a silent mutation. To estimate the frequency of this polymorphism in the normal population, 95 blood donors were analyzed: The gene frequency of the 8.5 kb (designated 'L') allele was 0.45 and that of the 8.65 kb ('U') allele 0.55. However, when 19 families with patients suffering from celiac disease were studied, the gene frequencies in the affected haplotypes (L = 0.76, U = 0.24) significantly deviated from those observed in the normal population and in the non-affected MHC haplotypes of these families (L = 0.48, U = 0.52). However, the association results from a strong association between the allele 'L' and the MHC haplotype HLA B8 DR3, a known suspectibility marker of celiac disease. Only one patient, in fact, was negative for the well-established class II haplotype markers DR3 or DR7. The data therefore confirm the crucial role of MHC class II in suspectibility to celiac disease, but due to a strong linkage disequilibrium within MHC the role of MHC class III genes in disease associations can not be ruled out.

The staining of HLA class II antigens, the presence of cells positive for interleukin-2

To investigate the origin of disease-associated IgM autoantibodies (AAb), we compared the genetic and structural characteristics of IgM AAb from autoimmune prone motheaten (mev) mice with natural autoantibodies (NAAb) from normal background C57/BL6 strain. Six hybridoma-derived IgM molecules each were obtained both from mev mice, at the terminal stage of systemic autoimmune disease, and from mitogen-stimulated C57/BL6 mice. These were randomly selected for VH J558 gene expression (aberrantly expressed in mev mice). The variable regions of the IgM molecules, both from autoimmune and normal mice, were encoded by unmutated germline VH genes. Disease-associated AAb from mev mice were predominantly encoded by the J558 subfamily 186.2, whereas five J558 subfamilies were utilized in NAAb originating from normal mice. Junctional diversity as a result of N or P nucleotide insertions and D-D fusions was noted among IgMs originating from both mev (mostly B-1 lymphocytes) and C57BL/6 (mostly B-2 lymphocytes) mice. Interestingly, all six J558+ IgMs from mev mice showed a restricted CDR3 length of 10 amino acids, with similar hydrophobicity indices. Four unique V-D-J rearrangements were observed among these IgMs. None of the IgMs were polyreactive and three of the six were subsequently observed to express monospecific autoreactivity with synthetic peptides (residues 81-92 and 37-53) representing segments of the T cell CD4-accessory molecule. Three IgM antibodies had hydrophilic arginine residues in their CDR3 heavy chain region. By contrast, all six J558+ IgMs from C57/BL6 mice had variable CDR3 length, distinct VDJ rearrangements and a local negative charge in the CDR3 region. Four of these IgMs demonstrated polyreactivity with multiple conserved autoantigens and, hence, were classified as NAAb. These findings provide evidence for either positive or impaired negative selection of B-1 lymphocytes secreting disease-associated IgM AAb in mev mice. This likely results from a reduced threshold of responsiveness to autoantigens due to PTP1C deficiency, which is targeted at the CDR3 length of the variable region of the heavy chain. In addition, characteristic differences in the size and hydrophobicity pattern of the CDR3 of the heavy chain allow structural distinction between monospecific disease-associated IgM AAb and the polyreactive IgM NAAb.

The methylation state of CCGG sites in and around the human ornithine decarboxylase gene, oncogenes c-myc and erb-A1, and actin genes were determined in human malignant leucocytes from patients with acute and chronic myeloid leukemia, chronic lymphatic leukemia, polycythemia vera, and multiple myeloma by means of isoschizomeric restriction endonuclease analysis. When compared with DNA from leucocytes of healthy controls, the ornithine decarboxylase and erb-A1 genes were substantially hypomethylated in all samples obtained from patients with chronic lymphatic leukemia. Hypomethylation of genes, particularly growth-related sequences, might be a crucial fact in the malignant transformation of human leucocytes. Its relatively simple detection from blood samples may prove clinically applicable in monitoring patients with chronic lymphatic leukemia.

The methylation state of CCGG sites in and around the human ornithine decarboxylase gene, oncogenes c-myc and erb-A1, and actin genes were determined in human malignant leucocytes from patients with acute and chronic myeloid leukemia, chronic lymphatic leukemia, polycythemia vera, and multiple myeloma by means of isoschizomeric restriction endonuclease analysis. When compared with DNA from leucocytes of healthy controls, the ornithine decarboxylase and erb-A1 genes were substantially hypomethylated in all samples obtained from patients with chronic lymphatic leukemia. Hypomethylation of genes, particularly growth-related sequences, might be a crucial fact in the malignant transformation of human leucocytes. Its relatively simple detection from blood samples may prove clinically applicable in monitoring patients with chronic lymphatic leukemia.