Participation of leukocyte function-associated antigen-1 and NK cells in the homing of thymic CD8+NKT cells to the liver

A distinct CD8+NKT cell population expressing TCRalpha/beta or TCRgamma/delta has been identified in liver and thymus. We wondered whether cell adhesion molecules play a role in the homing of CD8+NKT cells to the liver. The number of liver CD8+NKT cells was markedly reduced in leukocyte function-associated antigen (LFA)-1-/- mice compared with wild-type (WT) mice. The reduction was restricted to the liver only and no measurable alterations were found in other organs. In the liver of SCID mice reconstituted with thymocytes from LFA-1-/- or WT mice, the number of donor-derived CD8+NKT cells was comparable and the vast majority of these cells expressed TCRalpha/beta. In a reciprocal radiation thymocyte reconstitution system with LFA-1-/- and WT mice, LFA-1 expressed on liver cells other than CD8+NKT cells appeared to be required for the homing of thymic CD8+NKT cells to the liver. The accumulation of donor thymocyte-derived CD8+NKT cells in the liver of SCID mice was severely impaired by in vivo depletion of NK cells, but not of Kupffer cells. These results not only indicate that thymus provides a source for CD8+NKT cells expressing TCRalpha/beta in the liver, but also suggest that LFA-1 expressed on NK cells is involved in the homing of thymic CD8+NKT cells to the liver.     

The need for a novel generation of vaccines

Although empirical vaccine development was highly successful, it has now reached its limits. Vaccines are only efficacious against those pathogens which are primarily controlled by antibodies. Protection against many infectious agents, however, strongly depends on T lymphocytes. Thus, novel vaccines have to stimulate the combination of T lymphocytes that is required for an optimum protective immune response. Although identification of antigens remains crucial, novel vaccine design also needs to consider the best way of introducing these antigens to the immune system. Intracellular antigen compartmentalisation, the early cytokine milieu and the appropriate surface expression of co-stimulatory molecules are of major relevance for understanding how novel vaccines could induce a protective immune response mediated by T lymphocytes. Intracellular bacteria are controlled by T lymphocytes and efficacious vaccines against these pathogens are not available yet. In this treatise, two experimental vaccination strategies will be described in more detail. These encompass recombinant vaccine carriers expressing, and naked DNA constructs encoding, heterologous antigens. Both vaccination strategies proved to be protective in the model of experimental listeriosis of mice.     

Minimal progesterone support required for the maintenance of pregnancy in mice

A study of the degree of progesterone support required for the maintenance of various stages of pregnancy was undertaken in mice. Mated females were ovariectomized at various stages of pregnancy and progesterone and oestradiol support provided by s.c. Silastic implants with known release characteristics. In the earliest stages of pregnancy (days 1-5), very low concentrations of progesterone (<25% of normal physiological values) were sufficient to maintain pre-implantation stages and allow implantation. In the immediate post-implantation period (days 5-9), the development of implantation sites and decidualization required considerably higher progesterone support. In mid-pregnancy (days 11-14), progesterone alone could not maintain pregnancy unless present in very high amounts; however, the presence of oestradiol during this period lowered the progesterone requirements to well within the physiological range. This effect of oestradiol started on day 11 but required the level of oestradiol support to be kept within strictly defined limits, with high concentrations inducing abortion. Progesterone alone was able to maintain pregnancy from day 15. These results indicate that the minimal progesterone support required for pregnancy in mice varies considerably at different stages of pregnancy and is at least partly modulated by oestradiol.      

Outcome of patients with ventricular assist devices and acute renal failure requiring renal replacement therapy

The significance of acute renal failure (ARF) for patients treated with a ventricular assist device (VAD) is uncertain. There is little information on the outcome of patients who require renal replacement therapy during treatment with a VAD. A retrospective review was undertaken to evaluate the impact of renal failure requiring renal replacement therapy on such patients. Studied were 227 patients who were supplied with a VAD at the German Heart Institute Berlin. Fifty-five patients required renal replacement therapy during treatment with a VAD. These were compared with patients not needing renal replacement therapy (ARF and non-ARF groups). Significant differences for the end points of survival, heart transplantation, and discharge from hospital were observed in patients with ARF (p < 0.01). Survival was then analyzed according to indications for treatment with a VAD (bridge to transplantation or cardiac recovery after cardiotomy, transplantation, myocardial infarction, myocarditis, and endocarditis). Survival for bridge-to-transplantation patients was clearly influenced in a negative way by ARF (p < 0.01). For cardiac recovery patients, only a small difference in survival was observed (p = 0.05). We conclude that ARF is a negative predictor for bridge-to-transplantation patients. For cardiac recovery patients the impact of ARF on survival is marginally significant.     

Phenotypic characterization of CD8(+)NKT cells

We describe a novel CD8(+)NKT cell population expressing TCRalpha /beta or TCRgamma /delta. These CD8(+)NKT cells were prominent in the liver, and except for the thymus, virtually absent in other lymphoid organs. CD8(+)NKT cells expressed activation markers and comprised a high proportion of Ly49(+) cells. The development of the majority of CD8(+)NKT cells expressing TCRalpha /beta, but not TCRgamma /delta, depended on classical MHC class I. No CD8(+)NKT cells were detectable in young athymic mice, whereas the cells expressing TCRgamma /delta, but not TCRalpha /beta, appeared randomly in aged athymic mice. CD8(+)NK1(+) TCRalpha /beta cells showed polyclonal TCRVbeta usage and were virtually devoid of TCRValpha14. CD8(+)NK1(+) TCRgamma /delta cells predominantly expressed TCRVgamma1, 2 and 4, and Vdelta4, 5, 6 and 7. CD8(+)NKT cells, in particular those expressing TCRgamma /delta, were a major population in early life. IFN-gamma, but not IL-4, was induced in CD8(+)NKT cells by in vitro stimulation, independent of the TCRalpha /beta or TCRgamma /delta lineage. Hence, these cells represent a unique, though heterogeneous T cell population that shares markers with, but is distinct from, both conventional NKT cells and conventional CD8(+) T cells, and that may play a role in immune regulation.     

Protection against murine listeriosis by an attenuated recombinant Salmonella typhimurium vaccine strain that secretes the naturally somatic antigen superoxide dismutase.

A recombinant (r)-Salmonella typhimurium aroA vaccine strain was constructed which secretes the naturally somatic protein of Listeria monocytogenes, superoxide dismutase (SOD), by the HlyB/HlyD/TolC export machinery. Vaccine efficacy of the SOD-bearing carrier strain was compared with that of the p60-secreting construct, S. typhimurium p60s (J. Hess, I. Gentschev, D. Miko, M. Welzel, C. Ladel, W. Goebel, and S. H. E. Kaufmann, Proc. Natl. Acad. Sci. USA 93:1458-1463, 1996). Vaccination of mice with both constructs induced protection against a lethal challenge with the intracellular pathogen, L. monocytogenes. While the somatic listerial antigen, SOD, is immunologically uncharacterized, the naturally secreted protein of L. monocytogenes, p60, is known to be highly immunogenic. Our data emphasize the high vaccine potential of r-Salmonella constructs secreting antigens of somatic or secreted origin. Moreover, they suggest that the HlyB/HlyD/TolC-based antigen delivery system with attenuated Salmonella spp. as the carrier is capable of potentiating the immune response against foreign proteins independent from their immunogenicity in and display by the natural host.     

Application of mycobacterial proteomics to vaccine design: improved protection by Mycobacterium bovis BCG prime-Rv3407 DNA boost vaccination against tuberculosis

Information from comparative proteome analysis of Mycobacterium tuberculosis and Mycobacterium bovis bacillus Calmette-Guerin (BCG) principally allows prediction of potential vaccine candidates. Thirty-six M. tuberculosis DNA vaccine candidates identified by comparative proteome analysis were evaluated in the mouse model for protection against low-dose aerosol M. tuberculosis infection. We identified the DNA vaccine candidate Rv3407 as a protective antigen and analyzed putative major histocompatibility complex class I epitopes by computational predictions and gamma interferon Elispot assays. Importantly, we discovered that the DNA vaccine Rv3407 improved the efficacy of BCG vaccination in a heterologous prime-boost vaccination protocol. Our data demonstrate the rationale of a combination of proteomics, epitope prediction, and broad screening of putative antigens for identification of novel DNA vaccine candidates. Furthermore, our experiments show that heterologous prime-boost vaccination with a defined antigen boost "on top" of a BCG primer provides superior protection against tuberculosis over vaccination with BCG alone.     

Outbreak of carbapenem-resistant Pseudomonas aeruginosa producing VIM-8, a novel metallo-beta-lactamase, in a tertiary care center in Cali, Colombia

The prevalence of imipenem resistance among Pseudomonas aeruginosa isolates at a 195-bed tertiary care medical center in Cali, Colombia, rose from 2% in 1996 to 28% in 1997 and to over 40% in 2003. Many isolates showed high-level multiresistance, and phenotypic characterization suggested the spread of a predominant strain with minor variants. Sixty-six resistant isolates collected between February 1999 and July 2003 from hospitalized patients (n = 54) and environmental samples (n = 12) were subjected to a fuller analysis. Genetic fingerprints were compared by pulsed-field gel electrophoresis (PFGE) of SpeI-digested genomic DNA, and bla(IMP) and bla(VIM) genes were sought by PCR. PFGE and serotyping indicated that 52 of the 66 isolates belonged to a single strain, with 82% similarity; the PFGE pattern for this organism was designated pattern A. Two further pairs of isolates represented single strains; the remaining nine isolates were unique, and in the case of one isolate, no satisfactory PFGE profile could be obtained. The pattern A isolates were mostly of serotype O12 and were highly resistant to imipenem (MICs, 32 to >256 microg/ml), with this resistance decreased eightfold or more in the presence of EDTA. They yielded amplicons with bla(VIM)-specific primers, and sequencing of DNA from a representative isolate revealed bla(VIM-8), a novel allele with three polymorphisms compared with the sequence of bla(VIM-2). Two of these nucleotide changes were silent, but the third determined a Thr139Ala substitution. Only 4 of 13 resistant isolates (2 clinical isolates and 2 environmental isolates) assigned to other PFGE types carried bla(VIM) alleles, whereas the others were less multiresistant and mostly had lower levels of imipenem resistance (MICs, < or =32 microg/ml) which was not significantly reduced by EDTA. No bla(IMP) alleles were detected. During 2003, when the environmental study was undertaken, serotype O12 isolates with bla(VIM) were recovered from sinks and stethoscopes in the most-affected units, although not from the hands of staff; the problem declined once these reservoirs were disinfected and hygienic precautions were reinforced.     

Development of CD8 alpha/beta + TCR alpha beta intestinal intraepithelial lymphocytes in athymic nu/nu mice and participation in regional immune responses.

On the basis of the CD8 coreceptor expression, T-cell receptor (TCR)alpha beta-bearing intestinal intraepithelial lymphocytes (i-IEL) segregate into two populations. The CD8 alpha alpha + TCR alpha beta i-IEL develop thymus independently, whereas the CD8 alpha beta + TCR alpha beta i-IEL are generally considered to be thymus dependent. Flow cytometry analysis revealed a distinct population of CD8 alpha beta + TCR alpha beta i-IEL in individual athymic nu/nu mice. The i-IEL encompassing CD8 alpha beta + TCR alpha beta cells expressed potent cytolytic and interferon-gamma-producing activities. These findings demonstrate that CD8 alpha beta + TCR alpha beta i-IEL can develop in nu/nu mice independently from a functional thymus and suggest that these cells, directly or indirectly, perform biological functions in the gut.     

Gestörte alpha2-Adrenozeptorfunktion bei Hämodialysepatienten mit renaler Anämie — eine mögliche Ursache der Blutdrucksteigerung unter rekombinantem humanem Erythropoietin?

Summary Nine patients on maintenance hemodialysis and transfusion-demanding renal anemia (group A) were treated with rHuEPO 120 IU/kg i.v. three times per week. Hemoglobin-content was raised from 7.2±0.9 to 10.4±0.8 g/dl. In all patients blood pressure rose, three patients developed arterial hypertension. Mean diastoloic blood pressure was 66±12 and 78±16 mmHg (p<0.001) before and after rHuEPO. Rise in blood pressure was accompanied by a significant fall in plasma-noradrenaline-levels (from 498±100 to 383±75 pg/ml;p<0.05) and alpha₂-adrenoceptor-density (from 574±76 to 384±49;p<0.05). Compared to nine patients on maintenance hemodialysis and hematocrit over 30% (group B), patients with severe renal anemia (group A before treatment) had higher densities of alpha₂-adrenoceptors (574±76 vs. 218±32;p<0.001) despite higher plasma-noradrenaline-levels (498±100 vs. 399±63; n.s.). We suppose a anemia-related disturbance of alpha₂-receptor-function with the result of abolished receptor down-regulation and impaired vascular reagibility to vasoconstricting stimuli. With the correction of anemia receptor-function improves, receptor down-regulation as well as vascular reagibility is re-established resulting in augmented vascular resistance and higher blood pressure.

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Abkürzungen rHuEPO rekombinantes humanes Erythropoietin - teMAP mittlerer arterieller Blutdruck - RR Blutdrucknach RIVA-ROCCI - RBF regionaler Blutfluß - RPR regionaler peripherer Widerstand