Emergence of community-associated methicillin-resistant Staphylococcus aureus strains in the neonatal intensive care unit: an infection prevention and patient safety challenge

Methicillin-resistant Staphylococcus aureus (MRSA) infections cause significant morbidity and mortality in neonatal intensive care units (NICUs). We characterized the clinical and molecular epidemiology of MRSA strains colonizing NICU patients. Nasal MRSA isolates (n = 250, from 96 NICU patients) recovered through active surveillance from 2009 to 2014 were characterized with staphylococcal cassette chromosome mec (SCCmec) typing and detection of mupA (marker of high-level mupirocin resistance) and qacA/B (marker associated with chlorhexidine resistance). Factors associated with community-associated (CA-) or healthcare-associated (HA-) MRSA were evaluated. The overall prevalence of MRSA nasal colonization was 3.9%. Of 96 neonates in our retrospective cohort, 60 (63%) were colonized with CA-MRSA strains and 35 (36%) were colonized with HA-MRSA strains. Patients colonized with HA-MRSA were more likely to develop MRSA infections than patients colonized with CA-MRSA (13/35, 37% versus 8/60, 13%; p 0.007), although the interval from colonization to infection was shorter in CA-MRSA-colonized infants (median 0 days, range -1 to 4 versus HA-MRSA-colonized infants, 7 days, -1 to 43; p 0.005). Maternal peripartum antibiotics were associated with CA-MRSA colonization (adjusted odds ratio (aOR) 8.7; 95% CI 1.7-45.0); intubation and surgical procedures were associated with HA-MRSA colonization (aOR 7.8; 95% CI 1.3-47.6 and aOR 6.0; 95% CI 1.4-24.4, respectively). Mupirocin- and chlorhexidine-resistant MRSA was isolated from four and eight patients, respectively; carriage of a mupirocin-resistant strain precluded decolonization. CA-MRSA strains are prominent in the NICU and associated with distinct risk factors. Given community reservoirs for MRSA acquisition and transmission, novel infection prevention strategies are needed.

Hypercalcaemia and elevated 1,25(OH)(2)D(3) levels associated with disseminated Mycobacterium avium infection in AIDS

Hypercalcaemia may complicate granulomatous diseases, such as tuberculosis and sarcoidosis, and various AIDS-related opportunistic infections and malignancies. We report here two patients with AIDS and disseminated Mycobacterium avium infection who developed symptomatic hypercalcaemia several weeks after commencing antimycobacterial chemotherapy, and in whom inappropriately elevated 1,25(OH)(2)D(3)levels were documented. Although vitamin D supplementation may have contributed, no other cause for the hypercalcaemia was found. The biochemical and clinical similarities between these cases and other hypercalcaemic granulomatous diseases suggest a common mechanism related to macrophage activation and dysregulated vitamin D production.

Concerted dephosphorylation of the transcription factor NFAT1 induces a conformational switch that regulates transcriptional activity

NFAT transcription factors are highly phosphorylated proteins that are regulated by the calcium-dependent phosphatase calcineurin. We show by mass spectrometry that NFAT1 is phosphorylated on fourteen conserved phosphoserine residues in its regulatory domain, thirteen of which are dephosphorylated upon stimulation. Dephosphorylation of all thirteen residues is required to mask a nuclear export signal (NES), cause full exposure of a nuclear localization signal (NLS), and promote transcriptional activity. An inducible phosphorylation site in the transactivation domain contributes to transcriptional activity. Our data suggest that dephosphorylation promotes NFAT1 activation by increasing the probability of an active conformation, in a manner analogous to that by which depolarization increases the open probability of voltage-gated ion channels. This conformational switch paradigm may explain modification-induced functional changes in other heavily phosphorylated proteins.

Expression of cytokines and factors modulating apoptosis by human sinusoidal leucocytes

BACKGROUND/AIMS

Liver sinusoids contain a large population of spontaneously cytotoxic cells (NK cells), CD8+ T cells and macrophages. The physiological role of these leucocytes remains unclear. They may participate in immune surveillance and peripheral tolerance by deleting tumour cells, virus-infected cells and activated T cells as they traffic through the liver. In order to gain further information about the function of these leucocytes within the hepatic sinusoids, we examined their production of immunomodulatory cytokines and apoptosis-related molecules.

METHODS

Semi-quantitative polymerase chain reaction and immunohistochemistry were used to determine the spontaneous production of cytokines and apoptosis-related molecules by sinusoidal leucocytes isolated from donor liver preservation solution.

RESULTS

In comparison with matched peripheral blood mononuclear cells, sinusoidal leucocytes produced more mRNA for IL-10, IL-15, TNF-alpha, IL-18, IFN-gamma, FasL, perforin and granzyme. IL-4 and IL-12 were not detected and IL-2 was only faintly detected in the liver-derived CD4+ population. Less bcl-2 was expressed in liver-derived CD4+ and CD8+ cells in comparison with matched peripheral blood cell populations.

CONCLUSIONS

The cytokines produced spontaneously by sinusoidal leucocytes are consistent with their high level of activation and spontaneous cytotoxicity. Their strong expression of apoptosis-mediating molecules (FasL, perforin, granzyme and TNF-alpha) support a role for these cells in immune surveillance and peripheral tolerance induction.

Affinity-driven peptide selection of an NFAT inhibitor more selective than cyclosporin A

The flow of information from calcium-mobilizing receptors to nuclear factor of activated T cells (NFAT)-dependent genes is critically dependent on interaction between the phosphatase calcineurin and the transcription factor NFAT. A high-affinity calcineurin-binding peptide was selected from combinatorial peptide libraries based on the calcineurin docking motif of NFAT. This peptide potently inhibited NFAT activation and NFAT-dependent expression of endogenous cytokine genes in T cells, without affecting the expression of other cytokines that require calcineurin but not NFAT. Substitution of the optimized peptide sequence into the natural calcineurin docking site increased the calcineurin responsiveness of NFAT. Compounds that interfere selectively with the calcineurin-NFAT interaction without affecting calcineurin phosphatase activity may be useful as therapeutic agents that are less toxic than current drugs.

Role of donor leukocyte chimerism in establishing the etiology of neutropenia after liver transplantation

BACKGROUND

The quantitation of donor leukocyte chimerism may aid in establishing the etiology of neutropenia after liver transplantation.

METHODS

The incidence and clinical and laboratory characteristics of severe neutropenia were studied in adults who have undergone liver transplantation at our institution over the last 4 years.

RESULTS

Severe neutropenia developed in 5 of 156 patients (3%). The clinical and pathological features were nonspecific. In two patients with a delayed diagnosis of graft-versus-host disease (GVHD), donor leukocytes comprised > or = 50% of the circulating peripheral blood mononuclear cells. In a third patient, an earlier diagnosis of GVHD was suspected on the basis of a donor leukocyte count of 3-10% in the peripheral blood. In contrast, donor leukocyte chimerism was < or = 0.01% in two patients with probable drug-induced neutropenia

CONCLUSIONS

The determination of donor leukocyte chimerism has an important role in the investigation of neutropenia after liver transplantation, allowing early diagnosis and treatment of GVHD.

Histologic and immunohistochemical responses after aortic valve allografts in the rat

BACKGROUND

Human aortic valve allografts elicit a cellular and humoral immune response. It is not clear whether this is important in promoting valve damage. We investigated the changes in morphology, cell populations, and major histocompatibility complex antigen distribution in the rat aortic valve allograft.

METHODS

Fresh heart valves from Lewis rats were transplanted into the abdominal aorta of DA rats. Valves from allografted, isografted, and presensitized recipient rats were examined serially with standard morphologic and immunohistochemical techniques.

RESULTS

In comparison with isografts, the allografts were infiltrated and thickened by increased numbers of CD4+ and CD8+ lymphocytes, macrophages, and fibroblasts. Thickening of the valve wall and leaflet and the density of the cellular infiltrate was particularly evident after presensitization. Endothelial cells were frequently absent in presensitized allografts whereas isografts had intact endothelium. Cellular major histocompatibility complex class I and II antigens in the allograft were substantially increased. A long-term allograft showed dense fibrosis and disruption of the media with scattered persisting donor cells.

CONCLUSIONS

The changes in these aortic valve allograft experiments are consistent with an allograft immune response and confirm that the response can damage aortic valve allograft tissue.

Advanced donor-origin melanoma in a renal transplant recipient: immunotherapy, cure, and retransplantation

BACKGROUND

A kidney transplant recipient inadvertently contracted donor-origin melanoma, which was found to be very advanced at presentation. Withdrawal of immunosuppression failed to induce rejection, and interferon-alpha was required. When florid allograft rejection was in progress, the allograft was removed, before it was recognized that the transplanted melanoma was not being simultaneously rejected.

METHODS

Subsequent immunotherapy was required, which largely recapitulated treatment of recognized value in autologous melanoma and included interferon-alpha, use of cultured melanoma cells as tumor vaccine, pooled allogeneic cell vaccination, and adoptive immunotherapy using lymphokine-activated killer cells.

RESULTS

Prolonged immunotherapy eradicated the widespread malignancy, and the patient went on to a successful second renal transplant, with follow-up of over 24 months.

CONCLUSIONS

This unique case demonstrates the successful cure of advanced transplanted melanoma through the use of immunotherapy, which did not require sophisticated tumor vaccine technology, and successful retransplantation.

Cerebral histoplasmosis in an Australian patient with systemic lupus erythematosus

A 39-year-old woman with systemic lupus erythematosus suffered a prolonged neurological illness associated with very low levels of glucose in her cerebrospinal fluid (CSF). Six months later, and after numerous CSF investigations, Histoplasma capsulatum was cultured. To our knowledge, this is the first report of cerebral histoplasmosis in Australia in a patient who is not HIV positive.

Serum levels of interleukins 8 and 10, interferon gamma, granulocyte-macrophage colony stimulating factor and soluble CD23 in patients with primary sclerosing cholangitis

The presence of auto-antibodies and hypergammaglobulinaemia in patients with primary sclerosing cholangitis (PSC) suggest an overactive humoral immune system. Serum cytokines, measured using in-house double monoclonal sandwich ELISA, were used to assess the state of cellular and humoral immunity in this condition by comparison with sex and age matched normal controls and patients with alcoholic cirrhosis (AC). Soluble CD23 (sCD23) as a marker of humoral immunity was significantly elevated in PSC (N = 31) relative to patients with AC (N = 12) and the control group (N = 20) (P < 0.0001 and P < 0.001 respectively). Serum interleukin (IL) 10, as an anti-inflammatory cytokine and IL8, as a marker of neutrophil activation were significantly elevated in patients with PSC relative to those with AC and the controls (P < 0.001 and P < 0.05 respectively). Interferon gamma, as a marker of cellular immunity, and granulocyte-macrophage colony stimulating factor, a marker of monocyte/macrophage function were similar in all the groups. Cytokines and sCD23 were no different between patients with AC and the control group. While more than two thirds of the patients with PSC were positive for ANCA, there was no correlation between the presence of ANCA or ANCA titre and serum levels of either IL8, IL10 and sCD23. These results suggest exaggerated humoral immunity in PSC. The raised levels of IL10 and IL8 in PSC are discussed in the context of inflammatory bowel disease and liver dysfunction.

Selective inhibition of NFAT activation by a peptide spanning the calcineurin targeting site of NFAT

NFAT transcription factors play a key role in the immune response. The activation of NFAT proteins is controlled by calcineurin, the calmodulin-dependent phosphatase that is inhibited by the immunosuppressive drugs cyclosporin A and FK506. Here we identify a short conserved sequence in NFAT proteins that targets calcineurin to NFAT. Mutation of a single residue in this sequence impairs the calcineurin-mediated dephosphorylation and nuclear translocation of NFAT1. Peptides spanning the region inhibit the ability of calcineurin to bind to and dephosphorylate NFAT proteins, without affecting the phosphatase activity of calcineurin against other substrates. When expressed intracellularly, a corresponding peptide inhibits NFAT dephosphorylation, nuclear translocation, and NFAT-mediated expression in response to stimulation. Thus, disruption of the enzyme-substrate docking interaction that directs calcineurin to NFAT can effectively block NFAT-dependent functions.

Structure of the DNA-binding domains from NFAT, Fos and Jun bound specifically to DNA

The nuclear factor of activated T cells (NFAT) and the AP-1 heterodimer, Fos-Jun, cooperatively bind a composite DNA site and synergistically activate the expression of many immune-response genes. A 2.7-A-resolution crystal structure of the DNA-binding domains of NFAT, Fos and Jun, in a quaternary complex with a DNA fragment containing the distal antigen-receptor response element from the interleukin-2 gene promoter, shows an extended interface between NFAT and AP-1, facilitated by the bending of Fos and DNA. The tight association of the three proteins on DNA creates a continuous groove for the recognition of 15 base pairs.

Human liver transplant perfusate: an abundant source of donor liver-associated leukocytes

In vitro studies designed to examine the mechanisms of immune tolerance after liver transplantation in humans have been hampered by the difficulty in obtaining sufficient numbers of donor liver-associated leukocytes (LALs). We have investigated whether the ex vivo perfusion of donor livers releases a population of LALs that can be readily retrieved from the waste fluid. The mean number of cells recovered after Ficoll-Hypaque density-gradient separation was 2.6 +/- 0.5 x 10(8) cells, with a viability of 94% +/- 2%. The perfusate lymphocytes comprised mainly T cells (39% +/- 2%) with a very low CD4/CD8 ratio and natural killer (NK) cells (56% +/- 6%) with an increase in the proportion of the CD3-CD56+CD16- subset. The activation marker CD69 was present on the majority of the perfusate lymphocytes. These are the phenotypic characteristics that have been previously reported for lymphocytes isolated from hepatic sinusoids. In mixed lymphocyte reactions, the perfusate cells showed a marked increase in the ability to stimulate allogeneic responder cells, resulting in 353% +/- 78% (P = .003) greater incorporation of [3H]thymidine in responder cells when compared with stimulation by donor peripheral blood mononuclear cells. The results show that large numbers of viable donor lymphocytes can be readily isolated from the liver perfusate solution. These cells have the characteristics of liver-associated lymphocytes with a predominance of activated NK and CD8+ T cells. This population can now be used in in vitro assays to elucidate the influence of donor leukocytes on the development of graft acceptance.

An assessment of peripheral immunity in patients with sarcoidosis using measurements of serum vitamin D3, cytokines and soluble CD23

The aetiology of the peripheral anergy in sarcoidosis is unclear. To investigate this further we measured the serum levels of several factors important in different aspects of immune regulation to obtain a profile of those factors which promote and inhibit immune activation in sarcoidosis. Thirty-seven patients with sarcoidosis and 20 healthy controls of similar sex and age comprised the study group. Serum IL-10, interferon-gamma (IFN-gamma), soluble CD23 (sCD23), IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-1beta and tumour necrosis factor-alpha (TNF-alpha) were measured using in-house ELISAs. Vitamin D3 was measured using a radioreceptor assay. Serum levels of sCD23 and IL-10 were significantly elevated in patients with sarcoidosis relative to controls (median 13.9 versus 9.5 arbitrary units/ml, P<0.01 for sCD23, and 9.6 versus 5.0 pg/ml, P<0.04 for IL-10). Regardless of steroid therapy or disease activity, serum levels of IFN-gamma, TNF-alpha, IL-1beta, GM-CSF and IL-8 were no different in patients with sarcoidosis and controls. Vitamin D3 levels were significantly higher in patients with sarcoidosis versus normal controls (medians 78.0 versus 56.0, P<0.001), active sarcoidosis (n = 20) versus inactive disease (n = 17) (medians 81.5 versus 66.0, P<0.03) and active sarcoidosis versus controls (medians 81.5 versus 56.0, P<0.0002). The levels were no different between patients with inactive sarcoidosis and controls. We suggest that IL-10 and vitamin D3 may contribute to the peripheral anergy in sarcoidosis. The elevated serum sCD23 suggests an increase in peripheral humoral immunity. Consistent with a quiescent peripheral immune system, factors capable of monocyte/macrophage activation (TNF-alpha, IFN-gamma, GM-CSF and IL-8) were not elevated in the peripheral circulation.

Serum soluble CD23 but not IL8, IL10, GM-CSF, or IFN-gamma is elevated in patients with hepatitis C infection

The increased frequency of autoantibodies and B cell non-Hodgkins lymphoma (B-NHL) in hepatitis C virus (HCV) infection suggests dysregulated humoral immunity. Soluble CD23 (sCD23) is involved in B cell activation and proliferation and the serum levels are raised in autoimmune diseases and B cell lymphoproliferative disease. We compared the serum levels of sCD23 in patients with HCV infection with those in patients with alcoholic cirrhosis (AC) and in healthy controls. Serum levels of interleukin (IL) 8, IL10, granulocyte macrophage-colony stimulating factor, and interferon-gamma were assessed simultaneously to check for generalized nonspecific immune stimulation. In contrast to the essentially normal serum levels of these latter cytokines, the levels of sCD23 were raised in the patients with HCV compared to those with AC and the normal controls (medians 34.0, 10.1, and 11.1 arbitrary units, respectively; HCV vs AC P < 0.0004, HCV vs controls P < 0.0001, AC vs controls P > 0.8). These results confirm HCV-induced humoral immune dysregulation and invite comparison with primary Sjögrens syndrome and Epstein-Barr virus infection, both of which are also associated with raised levels of serum sCD23, autoantibodies, and B-NHL.

Peripheral blood chimerism following human liver transplantation

The aim of this study was to prospectively investigate the peak levels and kinetics of donor leucocyte chimerism in human recipients following liver transplantation. The peak levels of chimerism were observed within the first 48 hours following transplantation and ranged from 0.15% to 20% of total peripheral blood mononuclear cells. In all but one patient, who developed graft versus host disease, there was an early peak level of chimerism that declined over time such that donor leukocytes were only intermittently detectable after 3 to 4 weeks. In 8 patients who had no episodes of graft rejection, the peak level of donor leukocyte chimerism ranged from 1.3% to 20% (mean +/- SEM; 5.5% +/- 2.1%). In 3 patients who were treated for episodes of acute graft rejection during the first four postoperative weeks, the peak level of donor leukocyte chimerism ranged from 0.15% to 0.2% (0.18 +/- 0.02, P = .012). The results demonstrate a marked variation in the total number of donor leukocytes detectable in the peripheral blood early after liver transplantation and also, that lower levels of chimerism may be associated with lower rates of initial graft acceptance and a higher incidence of acute rejection.

Transcription factors of the NFAT family: regulation and function

As targets for the immunosuppressive drugs cyclosporin A and FK506, transcription factors of the NFAT (nuclear factor of activated T cells) family have been the focus of much attention. NFAT proteins, which are expressed in most immune-system cells, play a pivotal role in the transcription of cytokine genes and other genes critical for the immune response. The activity of NFAT proteins is tightly regulated by the calcium/calmodulin-dependent phosphatase calcineurin, a primary target for inhibition by cyclosporin A and FK506. Calcineurin controls the translocation of NFAT proteins from the cytoplasm to the nucleus of activated cells by interacting with an N-terminal regulatory domain conserved in the NFAT family. The DNA-binding domains of NFAT proteins resemble those of Rel-family proteins, and Rel and NFAT proteins show some overlap in their ability to bind to certain regulatory elements in cytokine genes. NFAT is also notable for its ability to bind cooperatively with transcription factors of the AP-1 (Fos/Jun) family to composite NFAT:AP-1 sites, found in the regulatory regions of many genes that are inducibly transcribed by immune-system cells. This review discusses recent data on the diversity of the NFAT family of transcription factors, the regulation of NFAT proteins within cells, and the cooperation of NFAT proteins with other transcription factors to regulate the expression of inducible genes.

Normal function of the transcription factor NFAT1 in wasted mice. Chromosome localization of NFAT1 gene

NFAT1 (NFATp), a cytosolic component of the nuclear factor of activated T cells (NFAT), is encoded by a single gene which was mapped to mouse chromosome 2 in the vicinity of the wasted (wst) locus. Although wasted mice display a severe immune disorder, they express normal levels of NFAT1 protein. The NFAT1 protein in wasted mice is properly regulated and possesses comparable DNA binding activity as that in their littermate controls. Therefore, the wasted phenotype is not due to a defect in the expression or early regulation of the NFAT1 protein.

Interaction of calcineurin with a domain of the transcription factor NFAT1 that controls nuclear import

The nuclear import of the nuclear factor of activated T cells (NFAT)-family transcription factors is initiated by the protein phosphatase calcineurin. Here we identify a regulatory region of NFAT1, N terminal to the DNA-binding domain, that controls nuclear import of NFAT1. The regulatory region of NFAT1 binds directly to calcineurin, is a substrate for calcineurin in vitro, and shows regulated subcellular localization identical to that of full-length NFAT1. The corresponding region of NFATc likewise binds calcineurin, suggesting that the efficient activation of NFAT1 and NFATc by calcineurin reflects a specific targeting of the phosphatase to these proteins. The presence in other NFAT-family transcription factors of several sequence motifs from the regulatory region of NFAT1, including its probable nuclear localization sequence, indicates that a conserved protein domain may control nuclear import of all NFAT proteins.

T-cell receptor stimulation elicits an early phase of activation and a later phase of deactivation of the transcription factor NFAT1

We show here that NFAT1 is rapidly activated, then slowly deactivated, by stimulation of T cells through their antigen receptor. Within minutes of T-cell receptor stimulation, NFAT1 is dephosphorylated, translocates from the cytoplasm into the nucleus, and shows an increase in its ability to bind to DNA. These changes are dependent on calcium mobilization and calcineurin activation, since they are also elicited by ionomycin and are blocked by the immunosuppressive drug cyclosporin A. After several hours of T-cell receptor stimulation, the majority of the NFAT1 in the cell reverts to its original phosphorylated form, reappears in the cytoplasm, and again displays a low affinity for DNA. Deactivation of NFAT1 is facilitated by phorbol 12-myristate 13-acetate and inhibitors of capacitative calcium entry and most likely reflects the slow return of intracellular free calcium concentrations towards resting levels. Our results suggest that calcineurin-dependent signalling pathways mediate the early activation of NFAT1, while phorbol 12-myristate 13-acetate-dependent feedback pathways contribute to the late deactivation. Persistent NFAT-dependent cytokine gene transcription in activated T cells may be mediated by other NFAT family proteins in addition to NFAT1 during the immune response.

Recombinant NFAT1 (NFATp) is regulated by calcineurin in T cells and mediates transcription of several cytokine genes

Transcription factors of the NFAT family play a key role in the transcription of cytokine genes and other genes during the immune response. We have identified two new isoforms of the transcription factor NFAT1 (previously termed NFATp) that are the predominant isoforms expressed in murine and human T cells. When expressed in Jurkat T cells, recombinant NFAT1 is regulated, as expected, by the calmodulin-dependent phosphatase calcineurin, and its function is inhibited by the immunosuppressive agent cyclosporin A (CsA). Transactivation by recombinant NFAT1 in Jurkat T cells requires dual stimulation with ionomycin and phorbol 12-myristate 13-acetate; this activity is potentiated by coexpression of constitutively active calcineurin and is inhibited by CsA. Immunocytochemical analysis indicates that recombinant NFAT1 localizes in the cytoplasm of transiently transfected T cells and translocates into the nucleus in a CsA-sensitive manner following ionomycin stimulation. When expressed in COS cells, however, NFAT1 is capable of transactivation, but it is not regulated correctly: its subcellular localization and transcriptional function are not affected by stimulation of the COS cells with ionomycin and phorbol 12-myristate 13-acetate. Recombinant NFAT1 can mediate transcription of the interleukin-2, interleukin-4, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor promoters in T cells, suggesting that NFAT1 contributes to the CsA-sensitive transcription of these genes during the immune response.

Immunosuppressive drugs prevent a rapid dephosphorylation of transcription factor NFAT1 in stimulated immune cells

The immunosuppressive drugs cyclosporin A and FK506 interfere with the inducible transcription of cytokine genes in T cells and in other immune cells, in part by preventing the activation of NF-AT (nuclear factor of activated T cells). We show that transcription factor NFAT1 in T cells is rapidly dephosphorylated on stimulation, that dephosphorylation occurs before translocation of NFAT1 into the cell nucleus, and that dephosphorylation increases the affinity of NFAT1 for its specific sites in DNA. Cyclosporin A prevents the dephosphorylation and the nuclear translocation of NFAT1 in T cells, B cells, macrophages, and mast cells, delineating at least one mechanism that contributes to the profound immunosuppressive effects of this compound.

Phosphorylation of the transcription factor NFATp inhibits its DNA binding activity in cyclosporin A-treated human B and T cells

Cyclosporin A (CsA) exerts its immunosuppressive effect by inhibiting the activity of nuclear factor of activated T cells (NFAT), thus preventing transcriptional induction of several cytokine genes. This effect is thought to be largely mediated through inactivation of the phosphatase calcineurin, which in turn inhibits translocation of an NFAT component to the nucleus. Here we report that CsA treatment of Raji B and Jurkat T cell lines yields a phosphorylated form of NFATp that is inhibited in DNA-binding and in its ability to form an NFAT complex with Fos and Jun. Immunoblot analyses and metabolic labeling with [32P]orthophosphate show that CsA alters NFATp migration on SDS-polyacrylamide gel electrophoresis by increasing its phosphorylation level without affecting subcellular distribution. Dephosphorylation by in vitro treatment with calcineurin or alkaline phosphatase restores NFATp DNA binding activity and its ability to reconstitute an NFAT complex with Fos and Jun proteins. These data point to a new mechanism for CsA-sensitive regulation of NFATp in which dephosphorylation is critical for DNA binding.

Only one of the two DNA-bound orientations of AP-1 found in solution cooperates with NFATp

BACKGROUND

The transcription factor AP-1 activates the expression of numerous genes in response to mitogenic stimuli. AP-1 regulates gene expression both through solitary binding to independent recognition sites and, in cooperation with various heterologous transcription factors, through targeting to composite response elements. The two subunits that make up the AP-1 heterodimer, Fos and Jun, possess identical residues at positions that make sequence-specific contacts to DNA. This degeneracy leaves the protein with no apparent way of orienting itself uniquely on DNA by differentially recognizing its two non-identical half-sites. Here, we have analyzed the orientation of the AP-1 basic-leucine-zipper (bZip) domain on a cognate site, both alone and in the cooperative complex formed together with the 'nuclear factor of activated T cells' (NFATp).

RESULTS

The results of affinity cleaving experiments demonstrate that, in solution, the AP-1 bZip binds DNA as a mixture of two orientational isomers. However, in the cooperative complex formed with NFATp on a composite response element, the AP-1 bZip adopts a single orientation, with Jun and Fos bound to the NFATp-proximal and NFATp-distal half-sites, respectively. Protein cross-linking experiments demonstrate that protein-protein contacts are responsible for this 'orientational locking'.

CONCLUSIONS

Our results demonstrate that, through protein-protein interactions, one protein can force another to adopt a single DNA-bound orientation. Thus, cooperative interactions between adjacent regulatory proteins can influence not only the energetics of their interactions with DNA, but also their precise geometric and stereochemical arrangement. Because orientational isomers present markedly different structures to the transcriptional apparatus, it seems likely that orientation will exert an effect on the ability to activate transcription.

A similar DNA-binding motif in NFAT family proteins and the Rel homology region

The cyclosporin-sensitive factor NFATp cooperates with Fos and Jun family proteins to regulate transcription of the interleukin 2 gene in activated T cells. We have defined a 187-amino-acid fragment of NFATp, located centrally within the protein sequence, as the minimal region required for DNA binding and for complex formation with Fos and Jun. The sequence of this region of NFATp shows a low degree of similarity to the Rel homology region. One specific short sequence in NFATp (RAHYETEG), located near the NH2 terminus of the DNA-binding domain, resembles a highly conserved sequence (RFRYxCEG) that is located near the NH2 terminus of the Rel homology region and that has been implicated in DNA binding by Rel family proteins. Mutational analysis demonstrates that the residues in this sequence that are identical in NFATp and Rel family proteins contribute to DNA binding by NFATp. Further, mutation of the threonine residue in this sequence to cysteine, as in Rel proteins, confers on NFATp a sensitivity to sulfhydryl modification similar to that of Rel family proteins. The results suggest that NFATp and Rel family proteins bind to DNA using similar structural motifs.

Expression of the transcription factor NFATp in a neuronal cell line and in the murine nervous system

The transcription factor NFATp, which has a central role in cytokine gene induction in T cells, was previously thought to be expressed only in T cells and other immune cells. Here we report that NFATp is also expressed in the rat PC12 pheochromocytoma cell line and in the murine nervous system. Antisera against T cell NFATp recognize proteins of similar apparent molecular weight in T cells, PC12 cells, and murine olfactory bulb. The immunoreactive proteins from PC12 cells and from olfactory bulb bind to an NFAT site of the murine interleukin-2 promoter with the same specificity as T cell NFATp. Immunohistochemical staining localizes NFATp to neurons, specifically to olfactory receptor neurons and to their terminals in the olfactory bulb. The presence of NFATp in the nervous system suggests that it has a role in the transcription of specific neuronal genes in response to increases in cytosolic calcium.

Delineation of a region in the B2 bradykinin receptor that is essential for high-affinity agonist binding

We have made mutations in the predicted sixth transmembrane segment of a rat B2 bradykinin receptor and analyzed the variant proteins by expressing them in COS-1 cells. Two amino acid substitutions reduced the affinity of the receptor for bradykinin (Phe261-->Val by 1600-fold; Thr265-->Ala by 700-fold) with comparatively little effect on the affinity for the bradykinin antagonists NPC17731 and D-Arg-[Hyp3,D-Phe7]bradykinin (where Hyp is hydroxyproline). Three other substitutions (Gln262-->Ala, Asp268-->Ala, and Thr269-->Ala) modestly reduced the affinity for bradykinin and for the antagonist D-Arg-[Hyp3,D-Phe7]bradykinin. Even the most dramatically affected mutated receptors were still able to couple, after bradykinin binding, to phosphatidylinositol turnover. The data suggest that bradykinin directly contacts the face of the sixth transmembrane helix formed by the residues Phe261, Gln262, Thr265, Asp268, and Thr269 or that this face of the helix is the site of intraprotein contacts that serve to stabilize the agonist-binding conformation of the receptor.

Identification of a B2 bradykinin receptor expressed by PC12 pheochromocytoma cells

We have used rat PC12 pheochromocytoma cells, a clonal cell line closely related to sympathetic neurons, to investigate reports that the bradykinin receptor expressed in the peripheral nervous system is distinct from the well-characterized B2 bradykinin receptor of smooth muscle. Although there have been reports that [Thi5,8,D-Phe7]bradykinin [where Thi is beta-(2-thienyl)alanine] is a full agonist at some sites in the peripheral nervous system, we find that in PC12 cells [Thi5,8,D-Phe7]bradykinin behaves as a competitive antagonist of bradykinin-stimulated phosphatidylinositol turnover. In particular, sufficient concentrations of [Thi5,8,D-Phe7]bradykinin completely block the increase in inositol bisphosphate and trisphosphate in response to 100 nM bradykinin; [Thi5,8,D-Phe7]bradykinin alone, at up to 10 microM, does not appreciably increase inositol bisphosphate and trisphosphate. In contrast to the absence of evidence for a distinctive neuronal receptor, we have found convincing evidence that the bradykinin receptor previously identified in smooth muscle is present in PC12 cells. Using the polymerase chain reaction, we have isolated a full-length cDNA encoding a bradykinin receptor that is expressed in PC12 cells and verified that its nucleotide sequence is identical except at a single position to that of the rat uterine B2 bradykinin receptor. When expressed in COS cells this uterine bradykinin receptor exhibits the same high affinity for [3H]bradykinin (Kd 4.4 nM), the same relative affinities for a series of kinin antagonists, and the same efficient coupling to phosphatidylinositol turnover (EC50 2.5 nM) as the receptor in PC12 cells. We interpret our data, and the findings of a number of pharmacological studies, as strengthening the view that the B2 receptor expressed in PC12 cells and in certain cells of the peripheral nervous system is identical to the receptor in rat uterine smooth muscle.

Molecular cloning of a complementary deoxyribonucleic acid encoding the thyrotropin-releasing hormone receptor and regulation of its messenger ribonucleic acid in rat GH cells

Rat pituitary GH cells have been used extensively to study the biochemical actions of TRH on lactotropic cells. To investigate the structure and regulation of the rat TRH receptor (rTRHR), we have cloned its cDNA from GH4C1 cells. Using the polymerase chain reaction with degenerate primers and pools of cloned cDNAs from a GH4C1 cDNA library, a fragment sharing high similarity to the mouse thyrotrope TRHR (mTRHR) was identified. Conventional library screening with this fragment was used to isolate a single cDNA. mRNA synthesized in vitro from this cDNA was injected into Xenopus oocytes, and a characteristic conductance response to TRH was detected by voltage clamp recording. DNA sequence analysis revealed a molecule of 412 amino acid residues, with 96% similarity to the mTRHR. However, in contrast to the mTRHR, the rTRHR had an additional 19 amino acid residues at its carboxy-terminus. A mRNA of about 4 kilobases was identified in GH3 cells. Regulation of the rTRHR mRNA concentration was studied in GH3 cells. Steady state rTRHR mRNA levels were decreased to 30% of the control level by incubation with TRH for 48 h and increased 4-fold by incubation with dexamethasone for 12 h. Southern blot analysis of genomic DNA from GH3 cells gave a simple banding pattern consistent with a single copy gene. We conclude that the rTRHR shares high primary sequence similarity to the mTRHR, but the rTRHR has an extension of 19 amino acids at its carboxy-terminus, which is lacking in the mTRHR.

Intestinal lymphokine-activated killer cells in inflammatory bowel disease

The role of non-specific cytotoxicity in the pathogenesis of inflammatory bowel disease (IBD) was investigated by assaying the natural killer (NK) and lymphokine-activated killer (LAK) cell activity of lamina propria mononuclear cells (LPMC) from 22 specimens of intestinal mucosa affected by IBD. Only minimal levels of NK activity were detected against K562 cells, as well as colon carcinoma cells, adenoma cells and fibroblasts freshly isolated from the intestinal mucosa. Culture of LPMC from IBD in the presence of interleukin-2 (IL-2) generated LAK cells that mediated high levels of activity against K562 cells and against neoplastic epithelial cells and fibroblasts derived from the intestinal mucosa. A group of 20 histologically normal specimens of intestinal mucosa showed similar levels of LAK activity against the K562 and intestinal cell targets. The minimal mucosal NK activity in IBD suggests that the cytotoxic properties of NK cells are not important in the pathogenesis of IBD. The presence of LAK precursor cells in the inflamed mucosa of IBD and their ability to lyse biologically relevant targets in vitro suggests that LAK cells have the potential to contribute to intestinal mucosal injury in IBD.

Allergic fungal sinusitis presenting as a paranasal sinus tumour

Allergic fungal rhinosinusitis is a rare complication of atopic upper airways disease which may present initially as an expansive tumour of the paranasal sinuses. This reported case was caused by the rare fungal pathogen Bipolaris hawiiensis and illustrates typical clinical and laboratory features of this disorder. Although the optimum management of allergic fungal sinusitis is controversial, combined therapy with surgical clearance, antifungal agents and corticosteroids produced a favourable outcome.

Magnetic resonance imaging of the delivery of a paramagnetic contrast agent by an osmotic pump

The successful application of Magnetic Resonance Imaging (MRI) in verifying the in vitro delivery action of an osmotically-driven pump (Alzet 2ML1) is described. MRI detection of drugs commonly used with such pumps is not yet possible because of the low signal intensity of present MR techniques. So we employed a paramagnetic contrast agent (gadolinium diethylene triamine penta acetic acid) of molecular weight comparable to commonly used drugs, and solutions of comparable concentration and viscosity. The study highlights the potential of this approach in the evaluation of in vivo drug delivery systems.

NMR measurement of the degree of oil/water partition of paramagnetic contrast media

Magnetic resonance imaging techniques have been used to evaluate the oil/water partition of a series of stable nitroxide free radicals. The degree of partition, K, closely parallels the order of chemical polarity and lipophilicity of these compounds. This method also provides insight into both their nuclear magnetic resonance relaxation characteristics and pharmacokinetics.

What are killer cells and what do they do?

Cytotoxic effector function of the immune system is mediated predominantly by killer cells and with the exception of complement-mediated lysis all forms of immune-directed cell death are attributable to these cells. The heterogeneous collection of cells with cytotoxic properties ranges from the phylogenetically primitive granulocyte and natural killer (NK) cell lineages to the more complex and versatile macrophage and antigen-specific cytotoxic T lymphocyte. Most killer cells are capable of the dual functions of cytotoxicity and immunoregulation. Granulocytes, macrophages and NK cells constitute an effective 'first line' cellular defence against invasive microbial pathogens and emerging malignancies. Through direct cytotoxicity or by the secretion of cytokines, NK cells also prevent overproliferation of precursor cell populations, thereby exerting a more discriminating control over antigen-specific T and B cell responses. The ultimate refinement of the killer cell is the cytotoxic T cell which is directed by an antigen receptor comparable in specificity and diversity to the immunoglobulin molecule. The mechanisms underlying the initial interaction between killer cell and target and the subsequent lytic event are imperfectly understood. Although many cytokines with lytic properties have been identified and in some cases cloned, their relative importance and intricate interactions with other components of the immune system are still largely unknown. In addition to the prevention of infection and malignancy, killer cells of all lineages are important in the pathogenesis of human disease. Of particular interest is the role of macrophages, NK cells and cytotoxic T cells in autoimmunity.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical characterisation of macrophages in human liver and gastrointestinal tract: expression of CD4, HLA-DR, OKM1, and the mature macrophage marker 25F9 in normal and diseased tissue

This report describes the immunocytochemical characterisation of macrophages in sections of human liver, gastrointestinal tract, and associated lymphoid tissue and the inflammatory lesions of Crohn's disease. 25F9 is an antigen reported to be induced during the maturation of blood monocytes in vitro. The antigen was concentrated in cytoplasmic vesicular structures of isolated gastrointestinal macrophages. Similar labelled cells were observed in the apical regions of lamina propria in both small and large intestine in vivo. Their numbers and size were greatly increased in specimens of colon from patients with melanosis coli. Mucosal inflammatory lesions in specimens from patients with Crohn's disease did not contain 25F9-positive cells. The antigen was absent from giant cells and epithelioid cells in granulomata but was expressed on histiocytes in submucosal microgranulomata. In lymphoid organs, 25F9-positive cells were found in germinal centres, in the dome region of Peyer's patch, and in the medulla, but were largely excluded from T cell areas. In reactive nodes from Crohn's disease patients, the number of labelled cells in germinal centres and T cell areas was greatly increased. 25F9 was absent from the majority of typical liver Kupffer cells, but was expressed on cytoplasmic granules in a minor subpopulation of larger, more rounded cells in the liver. The results suggest that 25F9 is a marker for endocytosis rather than maturation. In parallel sections, resident macrophages of both liver and gastrointestinal tract labelled with Leu 3a/OKT4 (CD4) and with OKIa (HLA-DR antigen) but did not express OKM1 (type III complement receptor). By contrast, OKM1 was present on inflammatory cells, epithelioid cells, and giant cells in mucosal lesions of Crohn's disease.

Lymphokine-activated and natural killer cell activity in human intestinal mucosa

The activity of natural effector (NE) cells was studied in lamina propria lymphocytes (LPL) obtained from 61 histologically normal specimens of human intestine, which included 45 resected for colon carcinoma and 16 resected for nonmalignant conditions. The mean spontaneous natural killer (NK) cell activity in LPL (1.7 X 10(2) cytotoxic units (C.U.)/10(5) cells) was very low in contrast to that found in peripheral blood mononuclear cells (PBMC) (38.5 X 10(2) C.U./10(5) cells). Significant NK activity was detected in only 16 (47%) of the tissues resected for carcinoma, and in five (38%) of those removed for nonmalignant conditions. Exposure to human leucocyte interferon resulted in only minimal increases in cytotoxicity for K562 target cells. Consistent with these findings, large granular lymphocytes represented less than 0.5% of freshly isolated LPL. Cultures of LPL from both carcinoma and nonmalignant conditions in MLA144-conditioned medium (CM), a source of interleukin 2 (IL 2), generated marked increases in cytotoxicity to levels comparable with or exceeding those found in PBMC. (Mean cytotoxicities were 90.4 X 10(2) and 49 X 10(2) C.U./10(5) cells, respectively.) Cytotoxicity induced by culture in MLA144-CM could be blocked by pretreatment of LPL with the monoclonal antibody anti-Tac directed against the IL 2 receptor. In addition, LPL cultured in recombinant human IL 2 were induced to levels of cytotoxicity that were similar to those induced by MLA144-CM. These data indicate that IL 2 is the factor in MLA144-CM responsible for generating lymphokine-activated killer (LAK) cells in LPL. The IL 2-activated LPL killer cells were OKT11+, OKT3-, Leu-7-, Leu-11b-, as determined by antibody and complement-mediated lysis, and the precursor cells in the lamina propria necessary for generation of killer cells by IL 2 were also OKT11+, OKT3-, Leu-7-, Leu-11b-. These studies indicate that LAK cells may be an important potential source of nonspecific cytotoxicity in the intestinal mucosa.

Lymphokine-activated and natural killer cell activity in human intestinal mucosa

The activity of natural effector (NE) cells was studied in lamina propria lymphocytes (LPL) obtained from 61 histologically normal specimens of human intestine, which included 45 resected for colon carcinoma and 16 resected for nonmalignant conditions. The mean spontaneous natural killer (NK) cell activity in LPL (1.7 X 10(2) cytotoxic units (C.U.)/10(5) cells) was very low in contrast to that found in peripheral blood mononuclear cells (PBMC) (38.5 X 10(2) C.U./10(5) cells). Significant NK activity was detected in only 16 (47%) of the tissues resected for carcinoma, and in five (38%) of those removed for nonmalignant conditions. Exposure to human leucocyte interferon resulted in only minimal increases in cytotoxicity for K562 target cells. Consistent with these findings, large granular lymphocytes represented less than 0.5% of freshly isolated LPL. Cultures of LPL from both carcinoma and nonmalignant conditions in MLA144-conditioned medium (CM), a source of interleukin 2 (IL 2), generated marked increases in cytotoxicity to levels comparable with or exceeding those found in PBMC. (Mean cytotoxicities were 90.4 X 10(2) and 49 X 10(2) C.U./10(5) cells, respectively.) Cytotoxicity induced by culture in MLA144-CM could be blocked by pretreatment of LPL with the monoclonal antibody anti-Tac directed against the IL 2 receptor. In addition, LPL cultured in recombinant human IL 2 were induced to levels of cytotoxicity that were similar to those induced by MLA144-CM. These data indicate that IL 2 is the factor in MLA144-CM responsible for generating lymphokine-activated killer (LAK) cells in LPL. The IL 2-activated LPL killer cells were OKT11+, OKT3-, Leu-7-, Leu-11b-, as determined by antibody and complement-mediated lysis, and the precursor cells in the lamina propria necessary for generation of killer cells by IL 2 were also OKT11+, OKT3-, Leu-7-, Leu-11b-. These studies indicate that LAK cells may be an important potential source of nonspecific cytotoxicity in the intestinal mucosa.

Alloreactive T-cell clones. Ly phenotypes predict both function and specificity for major histocompatibility complex products

We have studied the association of Ly phenotype with function and specificity for major histocompatibility complex (MHC) products by examining the properties of 21 T-cell clones derived from B10 anti-B10.D2 and B10.A anti-B10.D2 mixed lymphocyte cultures (MLC). T cells were selected after MLC solely on the basis of Ly phenotype, cloned by limiting dilution, and tested for stability of Ly phenotype, function and specificity for class I or class II MHC products. Sixteen Ly-1+2- and five Ly-1-2+ T-cell clones were tested. The clones selected for the Ly-1+2- phenotype maintained this phenotype, expressed helper but not lytic function, and recognized class II MHC products (I-Ad or I-Ed). All Ly-1-2+ clones maintained this phenotype, possessed cytolytic but not helper activity, and recognized class I MHC products (Dd and Ld). Our data therefore confirm at the clonal level the original observations of a remarkably consistent correlation between Ly markers, MHC specificity, and function. They suggest that the expression of Ly antigens on T-cell clones forms part of a genetic program for each of these specialized cells that also determines their function and MHC specificity.

Some rat sensory neurons in culture express characteristics of differentiated pain sensory cells

Sensory neurons were dissociated from trigeminal ganglia or from dorsal root ganglia of rats, grown in culture, and examined for expression of properties of pain sensory cells. Many sensory neurons in culture are excited by low concentrations of capsaicin, reportedly a selective stimulus for pain sensory neurons. Many are excited by bradykinin, sensitized by prostaglandin E2, or specifically stained by an antiserum against substance P. These experiments provide a basis for the study of pain mechanisms in cell culture.

Immunofluorescence studies of lung biopsy tissue

Thirty specimens of lung obtained by Abram's needle biopsy were examined using direct immunofluorescence. In 2 cases of Goodpasture's syndrome, linear deposits of IgG were demonstrated in alveolar walls. Diffuse deposits of IgG were found in the alveolar spaces of one patient with pigeon fancier's lung. Two subjects with cryptogenic fibrosing alveolitis had dense granular deposits of IgG in alveolar walls. Amorphous deposits of IgG were found in the pulmonary interstitium of a patient with desquamative interstitial pneumonitis. The small proportion of positive results obtained may reflect either the lack of a humoral immune background in the pathogeneses or only a fleeting involvement of humoral immunologic processes in each of the diseases studied. However, a small percentage of patients with diffuse interstitial disease do have antibody deposits demonstrable on small needle biopsy specimens. These require further investigation and may serve to define special groups. Various artifacts that were encountered led to difficulties in interpretation and these should be considered in reporting immunofluorescence studies of lung tissue. These included autofluorescence and nonspecific staining of connective tissue and cells. Nonspecific staining of eosinophils occurred frequently. The possible misinterpretation of artifacts as positive results is illustrated.

Burns in childhood: an epidemiological survey

The epidemiology of 382 burns admitted to the Royal Children's Hospital, Brisbane, is reviewed. Accidents due to burn trauma are disproportionately common among children when compared with adults, and during childhood years make up a sizable proportion of all injuries. In addition to the immediate physical trauma, there can be severe psychological consequences as well as severe disturbances to family life. Seventy per cent of the children in this series were normal active children less than four years of age, who were too young to learn that certain things are dangerous, and for this group preventative measures must be directed towards the parents. Possible methods of prevention of burns in children are discussed, and it is tragic that the very traits that make young children so engaging also lead them to accidental burn injuries. Their only hope of prevention lies in increased parental concern.