摘要:

In the last 2 years (1994–95), two symposium volumes and three reviews have been published that were fully devoted to peptide antibiotics (antibacterial peptides or antimicrobial peptides). Since the field has been growing rapidly, this review is largely a follow‐up of new results published in the last 2 years. Sequencing of the 16S RNA of the small ribosomal subunit indicate that the microbial world is much larger than generally appreciated. The importance of the natural flora is stressed and its effect on the evolution of peptide antibiotics and immunity in general is discus

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-76.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

MPB70 is secreted in high concentrations byMycobacterium bovisBCG substrain Tokyo (BCG Tokyo), but little by substrains Pasteur (BCG Pasteur) andM. tuberculosis. The gene encoding a MPB70 homologue secreted by BCG Tokyo was found at the upstream region of the gene encoding MPB70, with approximately 2.3 kilobase pairs (kbp) spacing: the same gene was also found in BCG Pasteur. This gene was cloned and sequenced from BCG Tokyo. The DNA sequence which contained a 663 base pair (bp) open reading frame beginning at position 1 and ending with a TAA codon at position 661 was found. Its theoretical molecular mass was calculated to be 22.068 kDa. This gene was highly homologous to the coding region ofmpb70and the deduced amino acid sequence was very similar to MPB83 reported by Harboeet al. It was speculated that the gene the authors characterized probably corresponded to thempb83 gen

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-68.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

TheMycobacterium bovisantigens MPB70 and MPB83 are homologous cross‐reactive proteins. It has been reported previously that MPB83 is glycosylated and exists in two forms with apparent molecular masses of 23 kDa and 25 kDa, whereas the apparent molecular mass of MPB70 is 22 kDa. Using a monoclonal antibody, SB10, which recognizes an epitope common to both MPB70 and MPB83, we compared the expression of these proteins inM. bovisBCG, virulentM. bovisand virulentMycobacterium tuberculosisby Western blotting of bacterial lysates. The previously described pattern of high and low producing substrains of BCG for MPB70 was also applicable for MPB83. VirulentM. boviswas found to express high levels of MPB70 and MPB83. Immunoblotting experiments using sera from Balb/c mice infected with liveM. tuberculosisH37Rv revealed that although the MPB83 homologue ofM. tuberculosis, MPT83, is expressed at low levels inM. tuberculosiswhen grownin vitro, the protein is highly immunogenic during infection with live bacteria. A clone from a mycobacterial shuttle cosmid library ofM. tuberculosisH37Rv was isolated which expressed both MPT70 and MPT83. Genetic analysis of this cosmid revealed that MPT70 and MPT83 were encoded by separate genes with the gene encoding MPT83 situated 2.4 kb upstream ofmpt70. Both genes are transcribed in the same direction. The gene encoding MPT83 was cloned and DNA sequencing revealed an open reading frame of 660 bp encoding a protein with a predicted molecular mass of 22 kDa. Recombinant MPT83 was expressed inEscherichia colifrom the native AUG initiation codon by translational coupling. InE. coliMPT83 was expressed as a 23 kDa antigen whereas in the rapid growing mycobacteriumMycobacterium smegmatisthe protein was expressed as a 25 kDa protein indicating post‐translational modification of the protein byM. smegmatis. In recombinantM. smegmatisMPT83 was predominantly cell associated whereas MPT70 was secreted into the culture medium. Amino acid sequence comparison between MPT83 and MPT70 revealed a 61% identity between the proteins, although little homology was apparent at the amino terminus. In MPT83 this region contained a typical lipoprotein signal peptide cleavage motif and a putative signal motif for O glycosylation. Both these motifs were absent from the amino aci

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-78.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

The murine T clone cells BK‐BI–2.6.O4.1 (BI/O4.1) synthesize and express MHC class II molecules constitutively. BI/O4.1 cells are able to present various protein antigens to antigen‐specific CD4+T cells. However, a 10‐fold higher concentration of antigen is needed to activate specific T cells to lymphokine secretion by BI/O4.1 cells in comparison with spleen cells or with the more homogeneous population of bone marrow‐derived macrophages (BMMph). The authors tested whether the reduced antigen presentation potential of BI/O4.1 cells was augmented by transferrin‐ mediated uptake of the model antigen ovalbumin (OVA) coupled to human ferric transferrin. It was shown that 240‐fold less OVA was sufficient to induce proliferation of an OVA‐specific T‐cell clone when the conjugate and not native OVA was used. The presence of ferric TF in the cultures competitively inhibited this effect of the conjugate. A similar shift in the dose–response curve to lower doses of antigen was induced by the conjugate when B lymphoma cells were used as antigen‐presenting cells. BMMph and P388D1 cells processed and presented the conjugate with similar efficiency as native OVA, although both cell types exposed transferrin receptors. These data suggest that the reduced antigen presentation potential of BI/O4.1 T clone cells is due to the inefficient uptake of OVA by pinocytosis and delivery into the p

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-77.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

Injection of mercuric chloride into Brown Norway (BN) rats induces a T lymphocyte‐dependent autoimmune syndrome. In order to investigate whether modification of adhesion and costimulatory molecules on T lymphocytes may be involved in early T lymphocyte activation by HgCl2, the authors analysed expression of these molecules in peripheral lymph node cells from BN rats at day 4 after injection of HgCl2. Tri‐colour flow cytometry was performed for expression analysis within CD45RC‐defined subsets of CD4+and CD8+cells. Compared to control rats, HgCl2‐exposed rats showed increased numbers of lymphocytes, especially of T lymphocyte blast cells. The levels of LFA‐1 expression as well as the fractions of ICAM‐1+cells were significantly increased in all CD45RC‐defined subsets of CD4+and CD8+cells. Within the CD4+CD45RCloT lymphocyte population, HgCl2‐injected rats showed a highly significant increase in the number of cells expressing OX40, which is a member of the TNF receptor family. Moreover, only CD4+CD45RCloblast cells of HgCl2‐exposed rats showed decreased expression of CD43, increased expression of CD49d and decreased numbers of CD26+cells. The results indicate that induction of autoimmunity by HgCl2in BN rats is associated with altered expression of T lymphocyte costimulatory molecules, predominantly on CD4+CD45RClocells, which may be caused by a direct effect of HgCl2on these cells, and may precipitate further activation of T and B ly

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-66.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

In order to analyse the diversity of T‐cell receptors (TCRs) expressed by the T‐cell population activated by allogeneic HLA‐DR stimulation, TCRβ cDNA was synthesized from mRNA of human CD4+T cells that had been stimulated in a primary mixed lymphocyte reaction (MLR). The TCRβ cDNA was amplified by the polymerase chain reaction (PCR), subjected to bacterial cloning, and sequenced from Vβ through Jβ. Twenty‐six different Vβ genes and 10 different Jβ segments were detected among 56 randomly selected cDNA clones. Occurrences of Vβ17.1 and Jβ1.5 were higher than those found in the CD4+T‐cell population activated with a CD3‐specific antibody. A total of 53 different CDR3 sequences, two of them occurring more than once, were detected among the 56 cDNA clones. In order to estimate the degree of CDR3 diversity, amino acid similarity in the CDR3 region of the cDNA was calculated and compared with those of the anti‐CD3‐activated T‐cell sequences as well as those of various published T‐cell clone sequences, each directed to either alloantigens or single antigenic peptides. It was found that the similarity score among CDR3 sequences obtained from the MLR (56.4 ± 10.3) was comparable to those of anti‐CD3‐activated T cells (55.7 ± 10.7) and those of T‐cell clones directed toward alloantigens (range, 48.4 ± 12.4−59.4 ± 13.1), but significantly smaller than those of T‐cell clones directed toward single antigenic peptides such as those derived from myelin basic protein (75.6 ± 17.9) and cytochromec(76.9 ± 20.5). These results provide quantitative proof that TCRs of T cells activated by primary allogeneic HLA‐DR stimulation hav

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-67.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

The authors have established a new immunodeficient mouse strain on the genetic background of the diabetes prone non‐obese diabetic (NOD) mouse. A deletion mutant of the RAG‐2 gene was back crossed 10 generations onto the NOD/Bom strain background. The homozygous NODrag−2−/−mice lack functionally mature B and T lymphocytes and do not develop insulitis or diabetes throughout life. In contrast, heterozygous NODrag−2+/−develop both insulitis and diabetes with an incidence similar to the wild type NOD mice. In transfer experiments, spleen cells from diabetic NOD donors were found to transfer disease to NODrag−2−/−recipients similar to what has been previously observed in transfer to irradiated NOD recipients or to immunodeficient NOD‐scid/scid mice. While resembling the recently established NOD‐scid/scid mice in many respects, the NODrag−2−/−mice represents an advantageous model for reconstitution of the pathogenesis of murine IDDM as it does not produce any endogeno

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-70.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

A specific receptor for interleukin‐8 has been identified on the surface of human monocytes using125I IL‐8 as a probe. A binding kinetic pattern shows that saturation was attained after 90 min and that the receptor was distinct from the receptors of other cytokines (IL‐1α, IL‐2, TNFα, GMCSF) and FMLP. Scatchard analysis of the binding data shows that 7000–10,000 receptors/monocyte are present with an equilibrium Kd 7 × 10−9 M. By immunoblot, the receptor for IL‐8 showed a sharp band with approximate M.W. 59 kD, consistent with the M.W. of IL‐8 receptor of neutrophils. In Boyden Chamber, monocytes migrated towards IL‐8 and the cytokine was observed to induce transient rise of intracellular Ca++in the cells. Thus, identification of functionally active IL‐8 receptor in monocyte may be helpful for understanding its p

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-69.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

A number of tumours and oncogene transformed cells displayed reduced MHC class I surface expression which seemed to enable their escape from immune surveillance. To test whether oncogenic activation is directly involved in suppressing MHC class I expression, a model of inducible oncogene expression was chosen. Mouse fibroblasts transfected with different oncogenes expressed under the control of the dexamethasone‐inducible MMTV promoter were analysed in the presence and absence of hormone for the mRNA and protein expression of MHC class I molecules as well as the respective oncogenes. Immunofluorescence analyses demonstrated an inverse association of MHC class I and oncogene expression after dexamethasone stimulation, independent of the type of oncogene causing transformation. Hormone‐mediated induction of oncogene expression caused down‐regulation of all H‐2 loci. Kinetic experiments using MMTV c‐Ha‐ras(A) transfectants revealed that down‐regulation of MHC class I surface expression was preceded by a dexamethasone‐induced change of morphology, anchorage‐independent growth, and an increase of the ras protein p 21. Parallel monitoring of mRNA expression demonstrated a time‐dependent up‐regulation of ras specific transcripts, which was associated with differential regulation of MHC class I heavy and light chain transcripts. β2‐microglobulin transcripts were transiently suppressed, whereas MHC class I heavy chain transcripts remained unaffected. To investigate the mechanisms of oncogene‐mediated down‐regulation of MHC class I expression, H‐2 promoter transfections and a nuclear run on assays were performed. In MMTV c‐Ha‐ras(A) cells, neither alterations of the H‐2 promoter activity nor of the transcriptional activity of H‐2 antigens was observed in the presence of dexamethasone, whereas both could be up‐regulated by interferon‐γ treatment. These data suggest that oncogene‐mediated transformation is directly associated with MHC class I down‐regulation, but that complex interactions affecting MHC class I heavy and light chain genes at the transcriptional and/or post‐t

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-73.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY

摘要:

The authors demonstrate that SEB immunization activates Vβ8+T cells and induces the acquisition of the primed phenotype as defined previously by low MEL‐14 and high Pgp‐1 expression. SEB‐activated spleen CD4+and CD8Vβ8+T cells have different population dynamics and regulate the expression of MEL‐14 and Pgp‐1 differentially, suggesting that the SEB‐MHC class II complex preferentially activates CD4Vβ8+T cells. Interestingly, at day 3 after SEB immunization, Vβ8+T cells expressing low, but not high, levels of MEL‐14 undergo apoptosis, indicating that T‐cell activation is a prerequisite for triggering programmed cell death. These results might help to trace antigen‐reactive cells to the activated or primed pool, as well as to identify those cells which will undergo

ISSN:0300-9475    

DOI:10.1046/j.1365-3083.1996.d01-75.x

出版商:Blackwell Science Ltd    

年代:1996

数据来源: WILEY