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Biomedical subjects

A Hennemann

Publications and source records attributed to A Hennemann.

14 recordsLinked to original sources
PubMed2001

The TCR-delta repertoire in normal human skin is restricted and distinct from the TCR-delta repertoire in the peripheral blood.

The skin and the intestinal mucosa form surfaces to external environments and share similarities in anatomic structure and immunologic defense. In healthy humans, intestinal gamma/delta T cells express a highly restricted gamma/delta T cell receptor repertoire whereas gamma/delta T cells of the skin were thought to express a polyclonal repertoire. Herein we report, using complementarity-determining region 3 size spectratyping and nucleotide sequencing of T cell receptor DV1 and DV2 rearrangements, that the human skin is also composed of clonally expanded gamma/delta T cells that are widely distributed. Identical complementarity-determining region 3 profiles and T cell receptor delta rearrangements were found in two separate skin samples that were obtained as far as 2-10 cm apart. Furthermore, analysis of peripheral blood mononuclear cells of these subjects clearly demonstrated that the skin harbors a unique population of gamma/delta T cells that is distinct from that in the peripheral blood. In addition comparable data were obtained irrespective of whether DNA or RNA was analyzed, indicating that the observed oligoclonality is not secondary to the expression of large amounts of mRNA from a few activated cells. Thus, gamma/delta T cells of the skin and the intestine both express an oligoclonal repertoire that enables them to respond to a variety of deleterious antigens without the need for diverse T cell receptors, possibly by recognition of stress-induced self-antigens or of conserved foreign antigens.

Clone Cells↗
PubMed2000

IgA and IgM V(H) repertoires in human colon: evidence for clonally expanded B cells that are widely disseminated.

BACKGROUND & AIMS: The mucosal immune system defends the body from pathogens to which the mucosal surfaces are continually exposed. Because lamina propria B cells should reflect the antigenic experience of the gut, we investigated their immunoglobulin (Ig) repertoire and distribution. METHODS: The junctional diversity of the IgA and IgM heavy-chain transcripts in the colon and the peripheral blood of healthy adults was analyzed by CDR3 size spectratyping and nucleotide sequencing. RESULTS: The V(H)6 and V(H)7 repertoires of intestinal IgA and IgM cells were oligoclonal, whereas the CDR3 profiles of the larger V(H)1-V(H)5 families suggested a more diverse repertoire with dominant bands superimposed on a polyclonal background. However, sequence analysis revealed multiple repetitive and clonally related transcripts at distant colonic sites from all V(H) families. This suggests that, in addition to a polyclonal B-cell pool, subsets of B cells are clonally expanded and widely distributed along the colon. Occasionally, there was evidence for B cells with the same CDR3 specificity, which exhibited an isotype switch from IgM to IgA. Circulating IgA B cells expressed a restricted V(H) repertoire that was distinct from that in the colon. CONCLUSIONS: The human colon contains widely disseminated B cells that express clonally related IgA or IgM receptors. These results are best explained by an antigen-driven process whereby intestinal memory B cells continuously recirculate.

Amino Acid Sequence↗
PubMed1997

The TCR-delta repertoire in human intestine undergoes characteristic changes during fetal to adult development.

The TCR-delta repertoire in adult human intestine is oligoclonal and unique in each individual. In the present study, changes in the junctional regions of TCR-delta transcripts in human intestine that occur during development from fetal to adult life were used to characterize fundamental changes in the TCR-delta repertoire in the human intestinal tract during ontogeny. At mid-gestation, the fetal repertoire was polyclonal, but limited, in its junctional diversity by the relative lack of N region nucleotide additions and by the frequent formation of coding region joins at regions of short sequence homology. In addition, identical TCRDV2 transcripts that resemble canonical TCR-delta sequences in mice were present in the intestine of different fetuses. In the early period after birth, the intestinal TCR-delta repertoire was polyclonal, and more diverse than the fetal repertoire, with junctional regions that contained extensive N nucleotide additions and frequently were as complex as those of adults. The intestinal TCR-delta repertoire showed increasing restriction with age and, by 14 to 17 yr, the repertoire was oligoclonal and resembled the repertoire of individuals in the sixth to seventh decade. Moreover, the adult TCR-delta repertoire was almost identical at multiple sites throughout the intestine, suggesting a model in which gammadelta T cell clones, selected by ligands in the intestinal tract, undergo expansion and recirculation before lodging throughout the small intestine or colon.

Adolescent↗
PubMed1996

Complete nucleotide sequence of Saccharomyces cerevisiae chromosome X.

The complete nucleotide sequence of Saccharomyces cerevisiae chromosome X (745 442 bp) reveals a total of 379 open reading frames (ORFs), the coding region covering approximately 75% of the entire sequence. One hundred and eighteen ORFs (31%) correspond to genes previously identified in S. cerevisiae. All other ORFs represent novel putative yeast genes, whose function will have to be determined experimentally. However, 57 of the latter subset (another 15% of the total) encode proteins that show significant analogy to proteins of known function from yeast or other organisms. The remaining ORFs, exhibiting no significant similarity to any known sequence, amount to 54% of the total. General features of chromosome X are also reported, with emphasis on the nucleotide frequency distribution in the environment of the ATG and stop codons, the possible coding capacity of at least some of the small ORFs (<100 codons) and the significance of 46 non-canonical or unpaired nucleotides in the stems of some of the 24 tRNA genes recognized on this chromosome.

Amino Acid Sequence↗
PubMed1994

(3H)dipyridamole and (3H)nitrobenzylthioinosine binding sites at the human parietal cortex and erythrocyte adenosine transporter: a comparison.

We compared the binding sites of the adenosine transport inhibitors (3H)dipyridamole (DPR) and (3H)nitrobenzylthioinosine (NBI) in human parietal cortex and erythrocytes. In comparison with guinea pig (3H)DPR marked only slightly more binding sites than (3H)NBI with a Bmax of 1080 +/- 29 and 780 +/- 7 fmol/mg protein respectively in parietal cortex and 24288 +/- 2725 and 20875 +/- 1905 fmol/mg protein respectively in erythrocytes. NBI displaced (3H)DPR binding completely from its binding sites at about KD/2 concentrations in parietal cortex as well as erythrocytes with inhibition constants comparable to its dissociation constants. Lineweaver-Burke analysis in erythrocytes indicated a competitive inhibition of (3H)DPR binding by NBI. Pharmacological characterization of (3H)DPR binding sites in human erythrocytes is consistent with their localization on adenosine transporters. These findings provide evidence that as opposed to guinea pig (3H)DPR and (3H)NBI largely label binding sites to the same adenosine transporter in human erythrocytes and parietal cortex.

Adenosine↗
PubMed1993

Nimodipine inhibits [3H]nitrobenzylthioinosine binding to the adenosine transporter in human brain.

The inhibition of [3H]nitrobenzylthioinosine ([3H]NBI) binding to human parietal cortex membranes by adenosine transport inhibitors, adenosine receptor agonists and antagonists and dihydropyridines was investigated. While the adenosine transport inhibitors inhibited [3H]NBI binding with Ki values in the low nanomolar range and the adenosine A1 receptor agonist, cyclopentyladenosine, with a Ki in the low micromolar range, no IC50 values could be obtained for the adenosine receptor antagonists at concentrations up to 100,000 nM. Among the dihydropyridines (+)-nimodipine was the most potent with a Ki of 201 +/- 55 nM. Inhibition of adenosine transport thus may contribute to the clinical effects of nimodipine in the central nervous system.

Dihydropyridines↗