Effector mechanisms in allograft rejection. IV. In contrast to late cytotoxic cells, and early killer cells infiltrating mouse sponge matrix allografts are predominantly T lymphocytes.

We have earlier demonstrated that a mixed population of immunologically specific killer cells, including cytotoxic T lymphocytes, non-T (“B”) lymphocytes and monocytes, infiltrate “sponge matrix” allografts at the peak of rejection on Day 8 after transplantation. We have now performed a sequential study covering both early and late stages of the rejection response. We demonstrate that the early infiltrating killer cells are sensitive to anti-Ø and anti-T cell serum plus complement treatment but the late killer cells are not. This finding indicates that the first cytotoxic host cells infiltrating the allograft are predominantly T lymphocytes, whereas as the rejection process proceeds also cytotoxic non-T (“B”) lymphocytes and monocytes are recruited to the site of inflammation.     

Survival of Escherichia coli in the environment: fundamental and public health aspects

In this review, our current understanding of the species Escherichia coli and its persistence in the open environment is examined. E. coli consists of six different subgroups, which are separable by genomic analyses. Strains within each subgroup occupy various ecological niches, and can be broadly characterized by either commensalistic or different pathogenic behaviour. In relevant cases, genomic islands can be pinpointed that underpin the behaviour. Thus, genomic islands of, on the one hand, broad environmental significance, and, on the other hand, virulence, are highlighted in the context of E. coli survival in its niches. A focus is further placed on experimental studies on the survival of the different types of E. coli in soil, manure and water. Overall, the data suggest that E. coli can persist, for varying periods of time, in such terrestrial and aquatic habitats. In particular, the considerable persistence of the pathogenic E. coli O157:H7 is of importance, as its acid tolerance may be expected to confer a fitness asset in the more acidic environments. In this context, the extent to which E. coli interacts with its human/animal host and the organism''s survivability in natural environments are compared. In addition, the effect of the diversity and community structure of the indigenous microbiota on the fate of invading E. coli populations in the open environment is discussed. Such a relationship is of importance to our knowledge of both public and environmental health.     

Common antigen of oval and biliary epithelial cells (A6) is a differentiation marker of epithelial and erythroid cell lineages in early development of the mouse

Abstract. The A6 antigen - a surface-exposed component shared by mouse oval and biliary epithelial cells - was examined during prenatal development of mouse in order to elucidate its relation to liver progenitor cells. Immunohistochemical demonstration of the antigen was performed at the light and electron microscopy level beginning from the 9.5 day of gestation (26–28 somite pairs).
Up to the 11.5 day of gestation A6 antigen is found only in the visceral endoderm of yolk sac and gut epithelium, while liver diverticulum and liver are A6-negative. In the liver epithelial lineages A6 antigen behaves as a strong and reliable marker of biliary epithelial cells where it is found beginning from their emergence on the 15th day of gestation. It was not revealed in immature hepato-cytes beginning from the 16th day of gestation. However weak expression of the antigen was observed in hepato-blasts on 12–15 days of gestation possibly reflecting their ability to differentiate along either hepatocyte or biliary epithelial cell lineages.
Surprisingly, A6 antigen turned out to be a peculiar marker of the crythroid lineage: in mouse fetuses it distinguished A6 positive liver and spleen erythroblasts from A6 negative early hemopoietic cells of yolk sac origin. Moreover in the liver, A6 antigen probably distinguishes two waves of erythropoiesis: it is found on the erythroblasts from the 11.5 day of gestation onward while first extravascular erythroblasts appear in the liver on the 10th day of gestation. Both fetal and adult erythrocytes are A6-negative.
In the process of organogenesis A6 antigen was revealed in various mouse fetal organs. Usually it was found on plasma membranes of mucosal or ductular epithelial cells. Investigation of A6 antigen's physiological function would probably explain such specific localization.     

A familial mutation in the testis-determining gene SRY shared by both sexes

A familial mutation in SRY, the gene coding for the testis-determining factor TDF, was identified in an XY female with gonadal dysgenesis, her father, her two brothers and her uncle. The mutation consists of a T to C transition in the region of the SRY gene coding for a protein motif known as the high mobility group (HMG) box, a protein domain known to confer DNA-binding specificity on the SRY protein. This point mutation results in the substitution, at amino acid position 109, of a serine residue for phenylalanine, a conserved aromatic residue in almost all HMG box motifs known. This F109S mutation was not found in 176 male controls. When recombinant wildtype SRY and SRY^F109S mutant protein were tested in vitro for binding to the target site AAC AAAG, no differences in DNA-binding activity were observed. These results imply that the F109S mutation either is a rare neutral sequence variant, or produces an SRY protein with slightly altered in vivo activity, the resulting sex phenotype depending on the genetic back-ground or environmental factors.This paper is dedicated by G. S. to Professor Ulrich Wolf on the occasion of his 60th birthday     

The metabolism of leukotrienes in blood plasma studied by high-performance liquid chromatography

The metabolism of leukotrienes (B4, C4, D4, and E4) within human plasma was studied and a simple sample preparation is presented. It was demonstrated that leukotriene E4 and leukotriene B4 were stable during incubation at 37 degrees C using the in vitro system. In contrast, leukotriene C4 was metabolized by gamma-glutamyl transpeptidase activities into leukotriene D4 which was further metabolized by dipeptidase activities of plasma into leukotriene E4. The transition state inhibitor of gamma-glutamyl transpeptidase L-serine-borate decreased the metabolism of leukotriene C4 in plasma. Dilution of plasma demonstrated that the dipeptidase was more active compared to the gamma-glutamyl transpeptidase. The metabolizing activities of plasma were functionally characterized by fractionating the plasma proteins.