Prevalence of factor V leiden mutation in patients with thrombosis in Tunisia.

This study determined the prevalence of inherited factor V Leiden mutation in a group of 128 thrombosis patients (102 with venous thrombosis and 26 with arterial thrombosis) attending a hospital in Sousse, Tunisia, and a control group of 100 with no history of thrombosis. Using an allele-specific PCR amplification technique, factor V Leiden was found in significantly more patients (20.3%) than controls (6.0%). The higher prevalence was significant in the subgroup of venous thrombosis patients but not in arterial thrombosis patients. The allele frequency was 3.5% in the normal Tunisian population. Screening Tunisian patients with venous thrombosis and their relatives for factor V Leiden may be justified.

Anti-histone reactivity in systemic lupus erythematosus sera: a disease activity index linked to the presence of DNA:anti-DNA immune complexes.

This study shows that purified murine monoclonal anti-DNA antibodies and human polyclonal anti-DNA antibodies (from systemic lupus erythematosus--SLE--patients), preincubated with DNA, acquire anti-histone reactivity. Conversely, DNAse I treatment of SLE patients' antibodies with anti-histone activity abolishes such activity. It has previously been demonstrated that anti-DNA antibodies bind to the cell membrane and recognize cell-surface polypeptides that have been identified with histones by partial sequencing. In a series of 33 sera from patients with clinically active disease and 29 sera from patients in clinical remission, positivity of an immunoblot analysis detecting antibodies against these polypeptides was associated with clinical activity of SLE (sensitivity, 0.88; specificity, 0.90). Anti-histone reactivity detected by ELISA appeared to be also a good marker of SLE activity (sensitivity, 0.64; specificity, 0.54). As expected, anti-native DNA antibody positivity and lowered complement dosage were also associated with clinical activity (sensitivity, 0.79 and 0.63, respectively; specificity, 0.48 and 0.93, respectively). Since anti-histone reactivity reflects, at least partly, the presence of anti-DNA antibodies complexed to DNA, which could bind to cell-membrane determinants, and is associated with disease clinical activity, it is suggested that this mechanism can contribute to explain the pathogenicity of anti-DNA antibodies.

A monoclonal anti-double-stranded DNA autoantibody binds to a 94-kDa cell-surface protein on various cell types via nucleosomes or a DNA-histone complex.

A crude supernatant of hybridoma secreting a monoclonal anti-double-stranded (ds)DNA antibody (PME77 mAb), used to stain fibroblasts (CVI cells) in immunofluorescence, gives a punctuated staining of variable intensity. We had suggested that anti-DNA antibodies bind to cell-surface protein(s) of several cells. When the mAb of this crude supernatant was purified on a dsDNA-cellulose column and a histone-Trisacryl column, the mAb no longer bound to the cell surface. Only when dsDNA plus purified histones was added to the purified antibody did the immune complex strongly and uniformly stain again the cell surface of CVI cells. No significant staining was observed if either DNA or histones were omitted. A signal 94-kDa protein from membrane fractions of CVI, Raji, and RINm cell lines was visualized in immunoblots when mAb-DNA-histone complexes were applied to the nitrocellulose strips. No polypeptide was seen if one component was omitted. This 94-kDa protein behaved like a plasma membrane protein since it required the use of detergent to be solubilized and was quantitatively recovered in the Triton X-114 detergent-rich phase. Moreover, a brief treatment of living cells with trypsin cleared off this protein. Purified nucleosomes could be substituted to DNA-histone complexes, giving rise to identical results. Finally, purified polyclonal anti-DNA antibodies from sera of systemic lupus erythematosus patients labeled a 94-kDa protein provided that DNA-histone complexes were added. Anti-DNA autoantibodies could be pathogenic when they are bound to nucleosomes.

Prevalence of factor V Leiden mutation in patients with thrombosis in Tunisia

This study determined the prevalence of inherited factor V Leiden mutation in a group of 128 thrombosis patients [102 with venous thrombosis and 26 with arterial thrombosis] attending a hospital in Sousse, Tunisia, and a control group of 100 with no history of thrombosis. Using an allele-specific PCR amplification technique, factor V Leiden was found in significantly more patients [20.3%] than controls [6.0%]. The higher prevalence was significant in the subgroup of venous thrombosis patients but not in arterial thrombosis patients. The allele frequency was 3.5% in the normal Tunisian population. Screening Tunisian patients with venous thrombosis and their relatives for factor V Leiden may be justified