Occurrence of a capsule in Aeromonas salmonicida

Aeromonas salmonicida grown in a medium with excess glucose as carbon source produces both capsular and exocellular polysaccharides. The capsular polysaccharide is composed of glucose, mannose, rhamnose, N-acetylmannosamine and mannuronic acid in the molar ratios of approximately 5:3:0.75:2:1. The extracellular polysaccharide is similarly constituted, but in the molar ratios of approximately 4.75:10.5:1.5:2:1. The capsular and exocellular polysaccharides did not cross-react with monoclonal antibodies against the A-layer or the O-antigen lipopolysaccharide.     

Autoimmunity after induction of neonatal tolerance to alloantigens: role of B cell chimerism and F1 donor B cell activation

BALB/c mice rendered tolerant by the neonatal injection of semiallogeneic (C57BL/6 X BALB/c)F1 spleen cells develop features of autoimmune disease. The possible mechanisms involved in autoantibody production, particularly anti-DNA antibodies, were investigated. In the first 5 wk, there was polyclonal B cell activation, as indicated by marked hypergammaglobulinemia, with a predominance of IgG1 and an increased production of antihapten antibodies. IgG1 anti-SSDNA and anti-DSDNA antibodies were detected with similar kinetics, but at higher titers than the anti-hapten antibodies. Also, there was a correlation between the effective induction of tolerance, as evaluated by the measurement of alloantigen-specific cytolytic T lymphocyte precursors, the persistence of B cell chimerism, and the production of anti-DNA antibodies. Anti-DNA antibodies were observed only in mice exhibiting a persistence of immunoglobulins bearing the donor's allotype. To determine the origin of anti-DNA antibodies, experiments were conducted whereby newborn BALB/c (Igh-1a) mice were injected with F1 cells from mice resulting from a crossing between Igh congenic BALB/c mice bearing the IgCHb allotype and conventional C57BL/6 mice (Igh-1b). All anti-DNA and anti-hapten antibodies exhibited the Igb allotype and thus were produced by the F1 donor B cells. The initial phase of tolerance induction was apparently associated with an allogeneic helper effect, because DNP-KLH-primed F1 donor cells transferred to newborn BALB/c could be stimulated after challenge with DNP-BGG. The triggering of persisting auto-reactive F1 donor B cells may reflect an activation by "incompletely" tolerant semiallogeneic T cells.     

Detection of Aeromonas hydrophila in food with an enzyme-linked immunosorbent assay

A microtitration plate, antibody capture, enzyme-linked immunosorbent assay was developed for the detection of Aeromonas hydrophila serotype O : 11 (highly virulent strains). The assay utilizes a detector antibody which shows no cross-reactions with Aeromonas strains other than serotype O : 11 or non- Aeromonas competing organisms. The detector antibody is mixed with the sample and incubated for 1 h, microcentrifuged and the supernatant fluid (unadsorbed antibody) titred in a microtitre plate coated with A. hydrophila cells from serotype O : 11. All the A. hydrophila strains from serotype O : 11 tested reacted strongly with the detector antibody. Also by culturing and performing the immunoassay with the detector antibody we established and quantified the presence of A. hydrophila O : 11 in different foods.     

Role of H-2 antigens in the host response to methylcholanthrene-induced tumors

H-2 loss variant sublines of a sarcoma (M-AS), induced by methylcholanthrene in an (A × A.SW)F₁ mouse, were used to study the role of the MHC products in the recognition of MC-TSTA. The two reciprocal variant sublines (M-A and M-S) were found to express the TSTA of the original tumor as shown by cross-reactions in graft rejection experiments performed in (A × A.SW)F₁ mice. In the A/Sn and A.SW mice the presence of the reciprocal parental H-2 antigens on the immunizing cells decreased the response against the tumor antigens. An admixture of lymphocytes derived from hyperimmune mice inhibited the outgrowth of the tumor cells. The growth inhibition was mediated by T cells and was H-2 restricted. Cells derived from hyperimmune syngeneic mice inhibited the outgrowth of the variant subline used for immunization but had no effect on the reciprocal variant subline.     

Using genetic variation to disentangle the complex relationship between food intake and health outcomes

Diet is considered as one of the most important modifiable factors influencing human health, but efforts to identify foods or dietary patterns associated with health outcomes often suffer from biases, confounding, and reverse causation. Applying Mendelian randomization in this context may provide evidence to strengthen causality in nutrition research. To this end, we first identified 283 genetic markers associated with dietary intake in 445,779 UK Biobank participants. We then converted these associations into direct genetic effects on food exposures by adjusting them for effects mediated via other traits. The SNPs which did not show evidence of mediation were then used for MR, assessing the association between genetically predicted food choices and other risk factors, health outcomes. We show that using all associated SNPs without omitting those which show evidence of mediation, leads to biases in downstream analyses (genetic correlations, causal inference), similar to those present in observational studies. However, MR analyses using SNPs which have only a direct effect on the exposure on food exposures provided unequivocal evidence of causal associations between specific eating patterns and obesity, blood lipid status, and several other risk factors and health outcomes.     

The role of penicillin amidases in nature and in industry

Penicillin amidase (PA) is the enzyme used commercially for the production of semisynthetic penicillins. During the past decade, a detailed picture of the structure and regulation of the gene encoding this enzyme has emerged, revealing a variety of interesting features that are unique among microorganisms. Clues to the biological role of this enzyme have been provided, as well as new strategies for the commercial production and utilization of PA.     

Mutations in the fumarate hydratase gene cause hereditary leiomyomatosis and renal cell cancer in families in North America

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant disorder characterized by smooth-muscle tumors of the skin and uterus and/or renal cancer. Although the identification of germline mutations in the fumarate hydratase (FH) gene in European families supports it as the susceptibility gene for HLRCC, its role in families in North America has not been studied. We screened for germline mutations in FH in 35 families with cutaneous leiomyomas. Sequence analysis revealed mutations in FH in 31 families (89%). Twenty different mutations in FH were identified, of which 18 were novel. Of these 20 mutations, 2 were insertions, 5 were small deletions that caused frameshifts leading to premature truncation of the protein, and 13 were missense mutations. Eleven unrelated families shared a common mutation: R190H. Eighty-one individuals (47 women and 34 men) had cutaneous leiomyomas. Ninety-eight percent (46/47) of women with cutaneous leiomyomas also had uterine leiomyomas. Eighty-nine percent (41/46) of women with cutaneous and uterine leiomyomas had a total hysterectomy, 44% at age < or =30 years. We identified 13 individuals in 5 families with unilateral and solitary renal tumors. Seven individuals from four families had papillary type II renal cell carcinoma, and another individual from one of these families had collecting duct carcinoma of the kidney. The present study shows that mutations in FH are associated with HLRCC in North America. HLRCC is associated with clinically significant uterine fibroids and aggressive renal tumors. The present study also expands the histologic spectrum of renal tumors and FH mutations associated with HLRCC.     

Autoimmune syndrome after induction of neonatal tolerance to alloantigens: effects of in vivo treatment with anti-T cell subset monoclonal antibodies

BALB/c (H-2d) mice rendered tolerant to h-2b alloantigens by neonatal injection of semiallogeneic (C57BL/6 X BALB/c)F1 spleen cells develop autoimmune features due to an abnormal activation of persisting F1 donor B cells. The role of T cells in this autoimmune syndrome was studied by in vivo treatment of tolerant mice with anti-L3T4(GK-1.5) or anti-Ly-2 (H-35-17.2) monoclonal antibodies. The treatment of tolerant mice from day 2 to day 21 of life with anti-L3T4 MAb completely prevented the occurrence of circulating immune complexes of anti-ssDNA anti-Sm and anti-hapten (FITC) IgG antibodies as well as the glomerular deposition of Ig that were usually seen in untreated tolerant mice. This effect persisted for at least 6 wk after stopping this treatment. When the injections of anti-L3T4 MAb were delayed until day 15 of life, a very significant decrease of the autoimmune manifestations was still observed. Treatment of tolerant mice with anti-Ly-2 MAb during the same period had no effects on the autoimmune disease as compared with untreated tolerant mice. No effects on the maintenance of tolerance vs H-2b alloantigens were observed after treatment with anti-L3T4 MAb, as followed by the decrease of CTL and CTL-p alloreactivity and by the persistence of F1 donor B cells, indicated by the presence of Ig bearing the Ighb donor allotype. These results suggest the existence of interactions between L3T4+ T cells and persisting autoreactive B cells from F1 donor origin in the development of the autoimmune syndrome after neonatal induction of transplantation tolerance.