High field magnetic transitions in the mixed holmium-yttrium iron garnet Ho(0.43)Y(2.57)Fe(5)O(12).

High static magnetic field magnetization measurements have been performed up to 23 T on Ho(0.43)Y(2.57)Fe(5)O(12) single crystals at helium temperature (T = 4.2 K) with fields applied along the three main cubic axes: [Formula: see text], [Formula: see text] and [Formula: see text]. The change from the spontaneous ferrimagnetic structure in zero magnetic field to the fully ferromagnetic one in high field takes place through several intermediate phases separated by transitions with step-like magnetization behaviour, but without any observed hysteresis. Using the effective spin Hamiltonian approximation, we show that the general features of these transitions can be accounted for by a large magnetocristalline anisotropy of the Ho(3+) moments of the uniaxial type along the local z axis of each rare-earth site. The model is in better agreement with the experiments than its Ising limit, widely used before, but is still unsuccessful in predicting the 'umbrella' magnetic structures found by previous neutron and NMR experiments.

Seroepidemiology of hepatitis B, C and delta viruses in Tunisia.

Serum samples from 33,363 healthy people in Tunisia have been tested for serological markers of hepatitis B, C and delta viruses (HBV, HCV and HDV). Hepatitis B surface antigen (HBsAg) was detected in 6.5% of sera. The overall seroprevalence of HBV was 37.5%. Vertical and perinatal transmission of HBV in the first 3 months of life occurred in only 0.4% of 177 mother and child pairs. HBV seroprevalence was 10.7% in infants under 5 years old and increased with age rapidly till 25 years of age and then more slowly in adulthood, reaching 54% for people aged over 40 years. HBsAg seropositivity varied throughout the country, ranging from 3% to 13% with higher prevalences in the south and central-west regions. Overall seroprevalences for HDV and HCV were 17.7% and 0.4%, respectively. HDV superinfection occurred later than HBV and increased with age in parallel with HBV. Overall, HCV and HBV infections had different geographical distributions throughout the country. The study confirmed the high prevalence of HBV infection in Tunisia; it occurs mainly in children and teenagers, and vertical and perinatal transmission of HBV does not appear to be significant. HDV superinfection is quite common in Tunisia and occurs in almost 44% of individuals infected with HBV. In contrast, seroprevalence of HCV in the Tunisian general population was low (0.4%). These results indicate differences in the distribution of the viruses and/or different routes of transmission.

[Primary, exclusively gastric localization of alpha-chain disease: anatomo-clinical and immunohistochemical study]. / Localisation gastrique primitive et exclusive d'une maladie des chaînes alpha: étude anatomo-clinique et immuno-histochimique.

We report the first case of heavy alpha-chain disease exclusively located in the stomach and in the perigastric nodes in a thirty year old Tunisian patient. Both the small bowel and the mesenteric nodes were evaluated histologically and immunochemically and were found to be free of disease. Complete remission was obtained using chemotherapy. The reasons for which the small intestinal mucosa and the mesenteric nodes, nearly constantly involved, in alpha-chain disease were spared in our case, are discussed.

[Successful treatment of chronic active hepatitis with high-dose intravenous immunoglobulins in agammaglobulinemia]. / Guérison d'une hépatite chronique active par immunoglobulines intraveineuses à fortes doses au cours d'une agammaglobulinémie.

BACKGROUND: Rapid progression of chronic active hepatitis can occur in patients with hypogammaglobulinemia. This report describes the successful use of i.v. immunoglobulins to treat chronic hepatitis in a child with agammaglobulinemia. CASE REPORT: A 17 month-old boy was admitted because he had suffered from recurrent infections since the age of 6 months. His family history was normal. Clinical and laboratory investigations showed hepatomegaly, agammaglobulinemia with absence of IgG, IgA, IgM and IgE, absence of beta cells, normal T cells, normal T cell proliferation and normal levels of complement, elevated ALAT (70 and 200 IU/ml) and ASAT (60 and 188 IU/ml). Liver biopsy showed typical features of chronic active hepatitis. The cause of this hepatitis (B and C virus, EBV, autoimmune markers) was not found. The patient was first given gammaglobulins (80 mg/kg) every week, subcutaneously, for 9 weeks, which did not change his transaminasemia. A second course of gamma-globulins, 400 mg/kg every 3 weeks, intravenously, for 6 months, resulted in a transient normalization of transaminases for 3 months. Definitive normalization was only obtained when the patient was given i.v. gammaglobulins (400 mg/kg/week) which gave a residual level of blood IgG of 10 g/l. This apparent cessation of hepatitis activity was confirmed by a second liver biopsy. The patient is now given i.v. gammaglobulins, twice a month, producing a residual blood IgG concentration of 5 g/l. CONCLUSIONS: The activity of this chronic hepatitis is closely correlated with the residual blood IgG concentration. Gammaglobulins could help neutralize virus extra-cellularly, although the viral origin of this hepatitis has not been-demonstrated.

[Primary immunodeficiency in Tunisia: study of 152 cases]. / Les déficits immunitaires primitifs en Tunisie: étude de 152 cas.

BACKGROUND: Primary immunodeficiencies are rare immunopathological disorders. A multidisciplinary study group was set up in Tunis in 1988 and has since identified 152 cases of such diseases. We herein present our series and compare it to the international registries. POPULATION AND METHODS: Over a period of 8 years (April 1988-April 1996), 295 children suffering from recurrent infections were investigated; primary immunodeficiency was confirmed in 152 out of them. The immunological investigation included a study of specific and/or non specific humoral and cellular immunity. RESULTS: These 152 patients belonged to 129 families among which 70 were consanguine (54%). Familial primary immunodeficiency occurred in 23 of them. In 39 families (30%), one or more deaths occurred during early childhood. In more than half of the cases (89 cases), the immunological investigations revealed a cellular or combined immunodeficiency with a majority of ataxia-telangiectasia syndromes (53 cases), T cell activation immunodeficiencies (12 cases) and HLA class II deficiency (nine cases). A predominant antibody defect was observed in 35 patients with a majority of agammaglobulinemia (11 cases) and hyper-IgM syndromes (11 cases). A defect of non specific cellular immunity was found in 18 cases (11.8%) including seven cases of chronic granulomatous disease and five cases of leukocyte adhesion deficiency. Three children (1.9%) were deficient in the complement system. Deaths occurred so far in 37 patients (24.3%). CONCLUSIONS: Primary immunodeficiencies are relatively frequent in Tunisia, probably because of the high rate of consanguinity among the general population. The distribution of the different groups of primary immunodeficiencies is characterized by high frequency of ataxia-telangiectasia and hyper-IgM syndrome and scarcity of severe combined immunodeficiencies and Wiskott-Aldrich syndrome.

[Rearrangement of immunoglobulin genes in alpha heavy chain disease: a criterion of monoclonality]. / Le réarrangement des gènes des immunoglobulines dans la maladie des chaines lourdes alpha: un critère de monoclonalité.

We have studied the configuration of genes encoding for the heavy and light chains in the tumoral cells of 6 patients affected by alpha heavy chain disease (alpha HCD). The results showed the presence of rearrangement of the alpha heavy chain as well as the kappa light chain genes whereas the lambda genes were in germinal configuration. Thus, these results suggest the presence of a monoclonal compound in the tumoral cells in the alpha HCD.

[Immunochemical analysis of human monoclonal IGM with antibody cold agglutinin activity during Mycoplasma pneumoniae infection]. / Analyse immunochimique d'une IgM monoclonale humaine à activité anticorps agglutinine froide au cours d'une infection à Mycoplasma pneumoniae.

Mycoplasma pneumoniae (MP) infection is associated with the emergence of anti-I cold agglutinins of IgM isotype, rarely complicated by hemolytic anemia. The mechanism by which the autoimmune disease occurs is still considerably controversed. We describe here a case of MP infection complicated by severe autoimmune hemolytic anemia with monoclonal anti-I IgM. IgM anti-I antibodies were purified by adsorption-elution on OI+ red cells. The red blood cell antibodies were found to be tightly associated with IgG and anti-MP specificity probably as immune complexes. The significance of these results is discussed.

Immunoregulatory role for a public IgM idiotype in the induction of autoimmune diseases in Mycoplasma pneumoniae infection.

Mycoplasma pneumoniae (MP) infection is associated with the emergence of various autoimmune disorders and autoantibody production. The most common autoantibodies induced are of anti-I specificity and express cold agglutinin (CA) activity. However, the mechanisms by which the microbial infection triggers the appearance of these autoantibodies are still unknown. To investigate these mechanisms, we used BALB/c mice as experimental models. In this paper, we show that BALB/c mice polyclonal antisera to MP react with human CA IgMs, and reciprocally, that BALB/c mice polyclonal antisera to human IgM CA react with MP. However, antibodies directed against MP and against CA IgM triggered by both immunizations represent two separate sets of antibodies. This was also confirmed using monoclonal antibodies derived from the immunized mice. Among these MAb we selected a monoclonal antibody MAb1D3 which reveals a cross-reactive idiotope (CRI) shared by human CA and other MIgMs with various autoantibody activities (anti-MAG and anti-IF). The CRI defined by MAb1D3 is a recurrent interspecies idiotope that is expressed by post infectious IgM antibodies to MP. Hence, we present in this study new data showing that the concomitant appearance of CAs and anti-MP IgM antibodies during acute MP infection is the consequence of a common idiotypic regulation of antibodies to infectious and to self antigens.

Quantitative and thermodynamic studies of erythrocytic ABO antigens.

This paper presents recent data from quantitative and thermodynamic investigations on A and B erythrocyte antigens. In regard to weak A phenotypes on the basis of quantitative data, practically no gap is observed from the weakest Aend to the strongest A3. Weak B phenotypes give a similar distribution. However, a more precise structural analysis including kinetics and thermodynamic measurements provides convincing evidence for the heterogeneity of each type of weak B reactive structures. Weak B antigens appear to be different from one to another, but similar inside one family. However, thermodynamics failed to demonstrate a qualitative difference between the weak B antigen in BX groups and the enhanced B antigen in ABX heterozygote, phenomenon that occurs in some very rare families. The same data were obtained from kinetic and thermodynamic analysis of B reactivity in cis AB samples; it can be assumed that such mutants are all different.

P phenotype observed in two generations of Tunisian family with a high rate of inbreeding.

A p phenotype was discovered in a Tunisian woman and in three of her seven children. This paradoxical result challenges the known hypotheses on this phenotype, which generally recognise that it is determined by the existence of a very rare allele in a double dose. The computation of the coefficient of inbreeding of these subjects showed that repeated intermarriages increased the coefficient of kinship of the propositus and her husband to 0.116 (if unknown women of the ancestry were assumed to be different for each child) through 0,1362 (if unknown women of the ancestry were assumed to be the same for sibs). Therefore inbreeding was proved to be so high as to induce the presence of a recessively defined phenotype in two successive generations. Moreover, the search for probability of origin of genes of the last generation showed that the BCH ancestor was probably the carrier of the p allele.

A human monoclonal IgG reactive with a private idiotope of a monoclonal IgM with autoantibody activity against myelin-associated glycoprotein.

One hundred and thirteen sera from patients with monoclonal IgG were tested for reactivity against a panel of 13 human monoclonal IgM having various autoantibody activities: 6 to myelin-associated glycoprotein (MAG), 2 to vimentin intermediate filament protein and 5 to red blood cell antigens [cold agglutinins with specificity directed to I antigen (3 cases), i antigen (1 case) or Pr antigen (1 case)]. One IgG was found to react with a monoclonal IgM with anti-MAG activity. This reactivity was characterized as idiotypic and directed against a private idiotope of the monoclonal IgM. This work provides further evidence for the existence of anti-idiotypic antibody activity of monoclonal Ig occurring in human B cell neoplasias.