Showing papers by "Eng M. Tan published in 1997"

Range of antinuclear antibodies in "healthy" individuals

Abstract: Objective. To determine the range of antinuclear antibodies (ANA) in “healthy” individuals compared with that in patients with systemic lupus erythematosus (SLE), systemic sclerosis (SSc; scleroderma), Sjogren's syndrome (SS), rheumatoid arthritis (RA), or soft tissue rheumatism (STR). Methods. Fifteen international laboratories experienced in performing tests for ANA by indirect immunofluorescence participated in analyzing coded sera from healthy individuals and from patients in the 5 different disease groups described above. Except for the stipulation that HEp-2 cells should be used as substrate, each laboratory used its own in-house methodology so that the data might be expected to reflect the output of a cross-section of worldwide ANA reference laboratories. The sera were analyzed at 4 dilutions: 1:40, 1:80, 1:160, and 1:320. Results. In healthy individuals, the frequency of ANA did not differ significantly across the 4 age subgroups spanning 20–60 years of age. This putatively normal population was ANA positive in 31.7% of individuals at 1:40 serum dilution, 13.3% at 1:80, 5.0% at 1:160, and 3.3% at 1:320. In comparison with the findings among the disease groups, a low cutoff point at 1:40 serum dilution (high sensitivity, low specificity) could have diagnostic value, since it would classify virtually all patients with SLE, SSc, or SS as ANA positive. Conversely, a high positive cutoff at 1:160 serum dilution (high specificity, low sensitivity) would be useful to confirm the presence of disease in only a portion of cases, but would be likely to exclude 95% of normal individuals. Conclusion. It is recommended that laboratories performing immunofluorescent ANA tests should report results at both the 1:40 and 1:160 dilutions, and should supply information on the percentage of normal individuals who are positive at these dilutions. A low-titer ANA is not necessarily insignificant and might depend on at least 4 specific factors. ANA assays can be a useful discriminant in recognizing certain disease conditions, but can create misunderstanding when the limitations are not fully appreciated.

The autoimmunity-inducing xenobiotic mercury interacts with the autoantigen fibrillarin and modifies its molecular and antigenic properties.

Abstract: The heavy metal mercury elicits a genetically restricted, anti-nucleolar autoantibody response that targets fibrillarin, a 34-kDa protein component of many small nucleolar ribonucleoprotein particles The mechanisms by which a toxin such as mercury elicits an autoantibody response that predominantly targets a single intracellular protein autoantigen remain uncertain, but may be prefaced by mercury gaining access to the intracellular environment Mercury-induced cell death was associated with loss of fibrillarin antigenicity and modification of the molecular properties of fibrillarin as revealed by aberrant migration under nonreducing conditions in SDS-PAGE Addition of mercury to isolated nuclei also resulted in aberrant migration of fibrillarin, but not other nuclear autoantigens The sensitivity of the HgCl2-induced modification of fibrillarin to 2-ME, iodoacetamide, and hydrogen peroxide suggested interaction of mercury with the two cysteines in the fibrillarin sequence This was confirmed by mutation of the cysteines to alanines, which abolished the aberrant migration of fibrillarin in the presence of HgCl2 The modification of the molecular structure of fibrillarin by mercury reduced immunoprecipitation by anti-fibrillarin autoantibodies, pointing to unmodified fibrillarin as the B cell Ag and implicating mercury-modified fibrillarin as the source of T cell antigenicity These observations demonstrate for the first time that an environmental toxin can alter the physicochemical properties of an autoantigen and may help to explain the antigenic specificity of mercury-induced murine autoimmunity

High frequency of neoplasia in patients with autoantibodies to centromere protein CENP-F.

Abstract: Objectif : Etudier les caracteristiques cliniques de patients qui ont des auto-anticorps de la proteine CENP-F du centromere et la frequence des auto-anticorps CENP-F chez des patients qui ont diverses maladies. Conception : Etude clinique et serologique retrospective. Methodes : On a identifie 36 patients atteints d'anti-CENP-F au moyen d'un trace caracteristique d'immunofluorescence indirecte (IFI) sur les cellules HEp-2. On a etudie aussi 50 patients atteints d'un melanome, 50 d'un cancer du sein, 10, d'un cancer du poumon, 354 souffrait de sclerodermie generalisee, 120, de lupus erythemateux dissemine et 50, de polyarthrite rhumatoide. On a produit des proteines recombinantes a partir de clones de 5 CENP-F de l'ADNc representant les acides amines 2192-3317 (p-F1), 5561-7126 (p-F2), 5892-6883 (p-F3), 7538-10116 (p-F4) et 9242-10096 (p-F5). On a etudie la presence de l'antigene CENP-F dans une souche de cellules de cancer du sein, des cryosections de cancer du sein, des tissus normaux du sein et des amygdales. Resultats : Vingt-deux des 36 patients qui avaient des anticorps CENP-F avaient des neoplasmes; on a diagnostique surtout des cancers du sein (9/22) et du poumon (5/22). Trente-trois serums etaient disponibles pour une etude plus poussee. Lorsqu'on en a analyse la reactivite aux peptides recombinants, les serums de 21 patients sur 21 qui avaient des neoplasmes et de 5 patients sur 12 qui avaient d'autres maladies ont lie le peptide p-F4 C-terminal. Lorsqu'on a etudie le tiers terminal du peptide p-F4 (p-F5), on n'a pas detecte de difference significative dans la tendance a la reactivite. Comme comparaison, la frequence de la reactivite avec des peptides representant d'autres domaines du CNP-F a ete inferieure a celle de la reactivite avec le p-F4 (p-F2 > p-F3 > p-F1). On n'a pas trouve d'auto-anticorps CENP-F dans aucun des serums temoins provenant de patients atteints de lupus erythemateux dissemine, de polyarthrite rhumatoide ou de sclerodermie generalisee, ou dans des serums non selectionnes provenant de diverses tumeurs malignes. On a identifie des antigenes CENP-F dans des tissus de cancer du sein, mais rarement dans des tissus normaux. Conclusions: Une proportion elevee d'individus qui ont des anticorps CENP-F ont des neoplasmes et ces serums presentent un biais en faveur de la reactivite avec des determinants dans le domaine carboxyle terminal du CENP-F. Les antigenes CENP-F semblent tres frequents dans les tumeurs malignes.

Heterochromatin protein hp1hsbeta (p25beta ) and its localization with centromeres in mitosis

Abstract: Some autoimmune sera containing anticentromere autoantibodies also recognize a doublet of Mr 23 000 (p23) and 25 000 (p25) in addition to CENP (centromere protein)-A (Mr 19 000), -B (Mr 80 000), and -C (Mr 140 000). A p25 antigen (HP1Hsα) has been shown to be a human homolog of Drosophila HP1 (heterochromatin protein 1). We have isolated a cDNA clone encoding another form of p25 (HP1Hsβor p25β) from a λZap HepG2 library using human autoimmune serum. The deduced amino acid sequence of the clone contained a conserved chromodomain (chromatin modifier domain) in the N-terminal region and a heterochromatin binding domain in the C-terminal region. In immunofluorescence experiments, only affinity purified antibodies reactive with the C-terminal (amino acids 70–185) domain showed nucleoplasmic and heterochromatin staining, whereas N-terminal (amino acids 1–115) specific antibodies were nonreactive. In metaphase chromosome spreads, the C-terminal domain antibody was also localized to the centromeric regions of chromosomes. Association with centromeres was most prominent at anaphase and changed to a more generalized association with whole chromosomes in telophase. The cooccurrence of autoantibodies to centromere proteins and HP1 in certain autoimmune diseases might be a reflection of coordinated immune responses to these closely associated sets of proteins.