Biomedical subjects

L Tussey

Publications and source records attributed to L Tussey.

5 recordsLinked to original sources

PubMed2000

Heparan sulfate proteoglycan isoforms of the CD44 hyaluronan receptor induced in human inflammatory macrophages can function as paracrine regulators of fibroblast growth factor action.

The CD44 glycoprotein is expressed in multiple isoforms on a variety of cell types where it functions as a receptor for hyaluronan-mediated motility. Recently, interest has centered on CD44 heparan sulfate proteoglycan (HSPG) isoforms because of their potential to sequester heparin-binding growth factors and chemokines. Expression of these isoforms on ectodermal cells has recently been shown to regulate limb morphogenesis via presentation of fibroblast growth factor (FGF) 4/FGF 8 while expression on tumor cells was shown to sequester hepatocyte growth factor and promote tumor dissemination. To date, however, CD44 HSPG expression in tissue macrophages and lymphocytes has not been adequately investigated, despite the fact these cells actively synthesize growth factors and chemokines and indirect evidence that monocyte CD44 sequesters macrophage inflammatory protein-1beta. Here we show primary human monocytes rather than lymphocytes express CD44 HSPGs, but only following in vitro differentiation to macrophages or activation with the proinflammatory cytokine interleukin-1alpha or bacterial lipopolysaccharide. Furthermore, we show these isoforms are preferentially modified with heparan rather than chondroitin sulfate, bind the macrophage-derived growth factors FGF-2, vascular endothelial growth factor, and heparin-binding epidermal growth factor with varying affinities (K(d) 25-330 nM) and in the case of FGF-2, can stimulate productive binding to the high affinity tyrosine kinase FGF receptor 1 (FGFR1). In contrast, we find no evidence for significant binding to C-C chemokines. Last, we confirm by immunofluorescent antibody staining that inflamed synovial membrane macrophages express CD44 HSPGs and that expression is greatest in cells containing high FGF-2 levels. These results suggest a paracrine role for macrophage CD44 HSPG isoforms in the regulation of growth factor action during inflammation.

Cell Differentiation↗

PubMed2000

Functionally distinct CD8+ memory T cell subsets in persistent EBV infection are differentiated by migratory receptor expression.

Human memory T lymphocytes have recently been re-defined as central or effector memory cells (Sallusto, F., Lenig, D., Forster, R., Lipp, M. and Lanzavecchia, A., Nature 1999. 401: 708-712). Effector memory cells (T(em)) are targeted to the peripheral tissues and show rapid effector function in response to antigenic stimulation. Central memory (T(cm)) cells are targeted to the lymph nodes and cannot be immediately activated. In this report HLA-A2-Epstein-Barr virus (EBV) peptide tetramers have been used to characterize the EBV-specific CD8+ T cell subsets in persistent EBV infection. In short-term activation studies two populations of tetramer-positive T cells were identified. One group resembled T(em) cells in that they rapidly produced IFN-gamma and lacked the lymph node homing receptor, CD62L, the second was similar to T(cm) cells since they were CD62L+ but could not be immediately induced to express IFN-gamma.

Antigens, CD↗

PubMed1995

HLA-A2 subtypes are functionally distinct in peptide binding and presentation.

Nearly half of HLA-A2-positive individuals in African populations have a subtype of HLA-A2 other than the A*0201 allele. We have isolated the common African HLA-A2 subtype genes from Epstein-Barr virus-transformed B cell lines and have established stable class I reduced transfectants expressing these alleles. We have studied the peptide binding and presentation properties of A*0201, A*0202, A*0205, A*0214, and A*6901 by a combination of approaches: assaying direct binding of labeled synthetic peptides, studying the ability of antigen-specific cytotoxic T lymphocytes to recognize peptide-pulsed cells, and sequencing peptide pools and individual ligands eluted from cells. We find that A*0201-restricted peptides can also bind to A*0202 but do not bind strongly to the other alleles in this study. We show that some cytotoxic T lymphocytes can recognize all subtypes capable of binding an antigenic peptide, whereas others are subtype specific. Sequencing of eluted peptides reveals that A*0202 has a similar peptide motif to A*0201, but that A*0205, A*0214, and A*6901 have different motifs. These data strongly support a model in which residue 9 (Phe or Tyr) of the A2/A68/A69 molecules is a critical factor in determining the specificity of the B pocket of the major histocompatibility complex and the position 2 anchor residue of associated peptides. We conclude that a single-amino acid difference in the major histocompatibility complex can be sufficient to cause a dramatic change in the nature of bound peptides, implying that individuals with closely related HLA subtypes may present very different repertoires of antigenic peptides to T cells in an immune response. It is likely to be a general phenomenon that very similar class I subtypes will behave as functionally distinct HLA allotypes.

Alleles↗

PubMed1995

Immunogenic HIV variant peptides that bind to HLA-B8 can fail to stimulate cytotoxic T lymphocyte responses.

Cytotoxic T lymphocyte responses in HIV infection can be impaired through variation in the epitope regions of viral proteins such as a gag. We report here an analysis of variant epitope peptides in three gag epitopes presented by HLA B8. Fifteen variant peptides were examined for their binding to HLA-B8; all but one bound at concentrations comparable to known epitopes. All except two of those that bound could be recognized by CTL from an HLA-B8 positive HIV-1-infected patient and were therefore immunogenic. However, in a hemophiliac patient studied in detail, there was a failure to respond to two immunogenic peptide epitopes representing virus present as provirus in the patient's peripheral blood. In one case, the patient's CTL had previously responded to the peptide; in the other case, there was a good response to a peptide of closely related sequence. Thus there was a selective failure of the CTL response to some proviral epitopes. This impaired reaction to new variants could contribute to the loss of immune control of the infection.

Animals↗

PubMed1989

Tissue-specific genetic variation in the level of mouse alcohol dehydrogenase is controlled transcriptionally in kidney and posttranscriptionally in liver.

Tissue-specific genetic variation in expression of the alcohol dehydrogenase, encoded by the Adh-1 gene, is found between C57BL/6J (B6) mice and B6.S congenic mice. B6.S mice contain a variant Adh-1 allele derived from a wild Danish strain in a B6 genetic background. B6 mice have nearly twice the alcohol dehydrogenase activity in liver but less than half the activity in kidney as B6.S mice. These tissue-specific genetic changes in alcohol dehydrogenase expression are manifest at the level of Adh-1-encoded mRNA. The regulatory site(s) involved act cis in both kidney and liver. These strains also differ in the extent to which androgen induces mRNA encoded by kidney Adh-1, with androgen increasing these levels 17-fold and 7.4-fold in the B6 and B6.S kidney, respectively. To identify the regulatory mechanism(s) underlying this strain variation in Adh-1 transcription in the B6 and B6.S kidney, liver, and androgen-induced kidney. For both uninduced and induced kidney, a difference in the transcription rate alone accounts for the strain difference in mRNA concentration. In contrast, because the Adh-1 transcription rate in liver does not differ significantly between B6 and B6.S mice, strain-specific variation in posttranscriptional regulation must be operative. Taken together these results indicate that the variation in Adh-1 expression between B6 and B6.S mice results from changes in both transcriptional and posttranscriptional control, and these controls are differentially operative in kidney and liver.

Alcohol Dehydrogenase↗