Identification and characterization of clinical isolates of members of the Staphylococcus sciuri group

A total of 28 staphylococcal isolates from human clinical specimens belonging to the Staphylococcus sciuri group were identified and characterized. The API Staph and ID32 STAPH correctly identified S. sciuri and S. lentus but not S. vitulinus strains. Identification to the subspecies level was possible only by a PCR-based method.     

T Cells Recognize Multiple GAD65 and Proinsulin Epitopes in Human Type 1 Diabetes, Suggesting Determinant Spreading

Human type 1 diabetes is thought to be mediated by autoreactive T cells specific for antigens expressed by pancreatic beta cells. However, it is unclear which autoantigens and determinants thereof are the targets of the autoimmune attack. Using comprehensive peptide libraries that cover the entire sequence of two major candidate autoantigens, GAD65 and proinsulin, we measured the in vivo frequencies of peptide-specific, IFN-gamma-producing memory T cells in 27 diabetic patients, 14 high risk individuals, and 15 partially HLA-matched healthy controls. Compared to the controls, both a higher number of determinants on the islet cell antigens were recognized and the frequencies of peptide specific cells were increased in patients and high risk individuals. Inclusion of signal enhancing anti-CD28 antibody further accentuated this difference. Considerable heterogeneity in peptide recognition was seen even in DRB1*04, DQB1*0302 matched individuals. Unlike its peptides, the GAD protein antigen did not recall a T cell memory response. The highly heterogeneous recognition of a multitude of peptide determinants on both autoantigens, occurring in the absence of protein recognition, and the low functional avidity of the memory cells involved jointly suggest that the autoimmune T cell repertoire in human type 1 diabetes primarily targets cryptic determinants engaged by determinant spreading.     

Airway hyper-reactivity mediated by B-1 cell immunoglobulin M antibody generating complement C5a at 1 day post-immunization in a murine hapten model of non-atopic asthma

Contact skin immunization of mice with reactive hapten antigen and subsequent airway challenge with the same hapten induces immediate airflow obstruction and subsequent airway hyper‐reactivity (AHR) to methacholine challenge, which is dependent on B cells but not on T cells. This responsiveness to airway challenge with antigen is elicited as early as 1 day postimmunization and can be adoptively transferred to naïve recipients via 1‐day immune cells. Responses are absent in 1‐day immune B‐cell‐deficient JH^?/? mice and B‐1 B‐cell‐deficient xid male mice, as well as in recipients of 1‐day immune cells depleted of cells with the B‐1 cell phenotype (CD19⁺ B220⁺ CD5⁺). As B‐1 cells produce immunoglobulin M (IgM), we sought and found significantly increased numbers of anti‐hapten IgM‐producing cells in the spleen and lymph nodes of 1‐day immune wild‐type mice, but not in xid mice. Then, we passively immunized naive mice with anti‐hapten IgM monoclonal antibody and, following airway hapten challenge of the recipients, we showed both immediate airflow obstruction and AHR. In addition, AHR was absent in complement C5 and C5a receptor‐deficient mice. In summary, this study of the very early elicited phase of a hapten asthma model suggests, for the first time, a role of B‐1 cells in producing IgM to activate complement to rapidly mediate asthma airway reactivity only 1 day after immunization.     

Hepatitis C viremia in HIV/HCV-coinfected patients: lower levels in presence of chronic hepatitis B

Complex reciprocal interactions between hepatitis C (HCV) and hepatitis B (HBV) viruses (HBV) have been reported. We examined the influence of HBV on HCV RNA titers in 376 HCV/HIV-coinfected patients (30 were also HBsAg positive). Regression analyses identified negative HBsAg and male sex as factors associated with HCV RNA values >500,000 IU/mL.     

Isolation of members of the Staphylococcus sciuri group from urine and their relationship to urinary tract infections

During a 3-year study period, 32,741 urine samples were analyzed for the presence of members of the Staphylococcus sciuri group (S. sciuri, S. lentus, and S. vitulinus), and 13 isolates were identified. They presented 0.79% of the total number of coagulase-negative staphylococci isolated. One case of symptomatic urinary tract infection and five possible cases of asymptomatic bacteriuria caused by these bacteria were established. It is noteworthy, however, that over 50% of the isolates originated from hospitalized patients.     

Selective induction of growth factor production and growth factor receptor expression by different signals to a single T cell

Stimulation of lymphokine production and the expression of receptors for growth factors can be dissociated in AK-8, a line of CD4+, I-A-restricted, conalbumin-specific mouse T cells. When activated by antibodies specific for the T cell receptor (TcR; F23.1) or the CD3 complex (145-2C11) adsorbed to plastic culture wells, AK-8 cells produce lymphokines but are unable to proliferate. Proliferation takes place using the same stimuli upon addition of interleukin 1 (IL 1). Autocrine growth induced by anti-TcR, anti-CD3 or by antigen is dependent on IL 4 and not on IL 2 in this cell line, as shown by the effect of antibodies against IL 4 or the IL 2 receptor. Similarly to plastic-adsorbed antibodies, phorbol myristic acetate (PMA) or a combination of PMA and the calcium ionophore Ionomycin also induces secretion of growth factors without inducing proliferation, but in this case addition of IL 1 is ineffective in inducing AK-8 proliferation. When incubated with anti-TcR or anti-CD3 antibodies in soluble form these cells neither proliferate nor produce IL 4 even in the presence of IL 1. However, soluble antibodies in the presence of IL 1 induce enhanced expression of IL 2 receptors, as measured both by induction of responsiveness to exogenous IL 2 or flow cytometry analysis using anti-IL 2 receptor antibodies. These results show that the pathways for the activation of growth factor receptor expression and the induction of lymphokine secretion can be differentiated in this cell line using anti-TcR or anti-CD3 reagents in different physical forms. The transmembrane signals delivered by these different forms of anti-receptor antibody may allow an understanding of these distinct requirements for T cell growth.     

Characterization of insulin resistance in type I diabetes

Summary Insulin sensitivity was assessed using the euglycaemic clamp technique in eight type I diabetic patients (after overnight blood glucose normalization with an artificial pancreas) and in six healthy subjects. Basal insulin concentrations were higher in diabetic patients (25±4 µU/ml) than in control subjects (17±1 µU/ml;P<0.05). Insulin infusion of 0.5, 1.0, 2.0 and 5.0 mU/kg per min during subsequent 2-h periods resulted in similar mean steady-state insulin concentrations in both groups. The mean dextrose requirements during the last 40 min of each period were nevertheless decreased in diabetic patients (1.6±0.5, 3.5±0.8, 6.5±0.7, 10.2±0.7 mg/kg per min) as compared with control subjects (4.7±0.3, 8.2±0.9, 10.2±0.9, 12.4±0.9 mg/kg per min). At low insulin concentrations dextrose requirements were diminished in all diabetic subjects. At the highest insulin levels, individual dose-response curves from only four patients were within the normal range. Under basal conditions, the monocyte receptor number was significantly reduced in diabetic patients (17,500±2,800 sites/cell) as compared with control subjects (26,700±2,500 sites/cell;P<0.05), whereas there were no differences regarding empty site affinities. Receptor data did not differ in patients with normal and decreased maximal dextrose requirements.Insulin resistance is apparently a common feature of type I diabetes at serum insulin concentrations of approximately 100 µU/ml. Normalization of the insulin effect by higher insulin concentrations is not possible in all patients. Insulin antibodies at concentrations observed in this study (<0.16 mU/ml) do not contribute significantly to insulin resistance; receptor and postreceptor defects are possibly more important.Abbreviations GCIIS Glucose-controlled insulin infusion system - SSGIR Steady-state glucose infusion rate I.N. and P.A. were fellows of the Deutscher Akademischer Austauschdienst 1981/82 and 1983/84     

Myotonia dystrophica with heart involvement: an electron microscopic study of skeletal, cardiac, and smooth muscle.

The electron microscopic features of the striated skeletal muscle, the striated cardiac muscle, and the smooth muscle from a woman who had been suffering for many years from myotonia dystrophica with cardiac involvement are described. The skeletal muscle was studied at two different stages of the disease. In the first material the main changes consisted of centrally situated nuclei, disorganisation of the sarcomeres, and focal disruption of the Z-line. The satellite cells were well represented. Three years later atrophy and degenerative, necrotic changes of the skeletal muscle were evident. The satellite cells were absent. Few changes were seen in the striated cardiac muscle. These consisted of slight interstitial fibrosis and large accumulations of mitochondria with intramitochondrial dense granules. The smooth muscle cells of the oesophagus showed disorientated filaments and mild degenerative changes. It is concluded that the skeletal muscle was more severely affected than the other types of muscle.     

Hirschsprung associated GDNF mutations do not prevent RET activation

Hirschsprung disease (HSCR) is a complex disorder characterised by aganglia of distal gastrointestinal tracts. The highest proportion of both familial and sporadic cases is due to mutations of the RET proto-oncogene. Five germline mutations in the glial cell-line-derived neurotrophic factor (GDNF) gene, one of the RET ligands, have been detected in HSCR patients. Pedigrees analysis and the observed association between these GDNF alterations and RET variants in the same patients raised the question of whether the GDNF gene plays any causative/predisposing role in HSCR pathogenesis. In the present work, we have studied the ability of GDNF proteins, each bearing one of the reported mutations, to activate RET by performing a functional test in cultured neuroblastoma cells. Consistently with the lack of genotype/phenotype correlation in human subjects, our results indicate absence of detectable alterations of mutant GDNF induced RET activation.