Investigation of hospital discharge cases and SARS-CoV-2 introduction into Lothian care homes

BACKGROUND

The first epidemic wave of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Scotland resulted in high case numbers and mortality in care homes. In Lothian, over a third of care homes reported an outbreak while there was limited testing of hospital patients discharged to care homes.

AIM

Investigate hospital discharges as a source of SARS-CoV-2 introduction into care homes during the first epidemic wave.

METHODS

A clinical review was performed for all discharges from hospitals to care homes starting 1st March 2020 to 31st May 2020. Episodes were ruled out based on coronavirus disease (COVID-19) test history, clinical assessment at discharge, whole genome sequencing (WGS) data and an infectious period of 14 days. Clinical samples were processed for WGS, and consensus genomes generated were used for analysis by cluster investigation and virus epidemiological tool (CIVET). Patient timelines were obtained using electronic hospital records.

FINDINGS

In total 787 hospital discharges to care homes were identified. Out of these 776 (99%) were ruled out for hospital discharge introduction. However, for 10 episodes the results were inconclusive as there was low genomic diversity in consensus genomes or no sequencing data. Only one discharge episode had a genomic, time and location link to positive cases during hospital admission leading to 10 further positive cases in the care home.

CONCLUSION

Majority of hospital discharges were ruled out for introduction into Lothian care homes highlighting the importance of screening all new admissions when faced with a novel emerging virus and no vaccine available.

Tolerance to lipopolysaccharide involves mobilization of nuclear factor kappa B with predominance of p50 homodimers

Stimulation of the human monocytic cell line Mono Mac 6 with lipopolysaccharide (LPS) leads to rapid and transient expression of cytokines like tumor necrosis factor (TNF). When such cells are precultured for 2 days with a low dose of LPS (20 ng/ml) followed by stimulation with a high dose of LPS (1 microgram/ml), expression of the TNF gene is minimal, i.e. the cells are tolerant. In nuclear run-on analysis, such tolerant cells show only a low degree of transcription, indicating that tolerance operates at or upstream of the transcription level. The CD14 LPS receptor is, however, up-regulated (not down-regulated) in tolerant cells, and LPS can, in fact, still lead to activation of tolerant cells as evidenced by mobilization of the transcription factor nuclear factor kappa B (NF-kappa B). Resolution of the NF-kappa B complex in gel shift analysis shows that the binding protein, mobilized in naive Mono Mac 6 cells, consists mainly of p50-p65 heterodimers, while in tolerant cells, the p50 homodimer is predominant. This increase in p50 homodimers coincides with an increase in p105 mRNA, suggestive of a transcriptional up-regulation of p50. Reporter gene analysis reveals that the NF-kappa B complex mobilized in tolerant cells is functionally inactive in that NF-kappa B-dependent luciferase constructs containing the human immunodeficiency virus long terminal repeat or the TNF 5'-region show only minimal transactivation after LPS stimulation. Similar to Mono Mac 6 cells, primary blood monocytes, when precultured with a low dose of LPS, also become tolerant and produce little TNF after LPS stimulation. The tolerant blood monocytes also up-regulate CD14, and they mobilize NF-kappa B with a predominance of p50 homodimers. Taken together, these results demonstrate that tolerance to LPS is determined by post-receptor mechanisms that involve an altered composition of the NF-kappa B complex.

Distinct patterns of differentiation induced in the monocytic cell line Mono Mac 6

The human Mono Mac 6 cell line exhibits many characteristics of mature blood monocytes including expression of the CD14 molecule and production of cytokines, such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor. To determine whether these cells can be further differentiated, we treated the cells for up to 3 days with either prostaglandin E2 (PGE2; 10(-5) or 10(-6) M), lipopolysaccharide (LPS; 10-20 ng/ml), or tetradecanoylphorbol-13-acetate (TPA; 10-50 ng/ml). All three reagents reduced proliferation and expression of the early myelomonocytic antigen CD33, and all increased phagocytosis of staphylococci and constitutive expression of mRNA for the macrophage colony-stimulating factor (M-CSF) receptor. By contrast, with respect to CD23 (Fc epsilon RII) expression, CD14 expression, and production of O2-, the three reagents induced distinct responses. Expression of CD23 (Fc epsilon RII) on Mono Mac 6 cells (36%) was not increased by LPS and TPA but was increased by PGE2 treatment to 48%, with a 50% increase of fluorescence intensity. The CD14 antibody My4 stained more than 75% of untreated Mono Mac 6 cells with a specific mean fluorescence intensity of 87.5 channels. This staining was increased more than twofold by both PGE2 and LPS. Staining with the CD14 antibody UCHM1 (6%) was increased to 43% by PGE2 and to 43% by LPS. This increase in CD14 cell surface expression was accompanied by a rise in soluble CD14 and enhancement of CD14 mRNA. By contrast, TPA treatment resulted in a twofold decrease of CD14 cell surface staining with no significant change in sCD14, while CD14 mRNA was transiently down-regulated. Secretion of O2- (stimulated by TPA) was already detectable in untreated Mono Mac 6 cells (6.1 mmol/10(6) cells/30 min), and this response was enhanced 10-fold by pretreatment with LPS but not with PGE2 or TPA. The kinetics of M-CSF receptor mRNA, CD14 expression, and O2- production revealed that these monocytic features started to increase at 6-24 h and were maximal at 2 days. These data suggest that the three reagents induce maturation of the Mono Mac 6 cells to different levels or into different branches of the monocyte system with the notable differences that PGE2 enhances CD23 expression, LPS enhances O2- secretion, and TPA down-regulates CD14.

Constitutive monocyte-restricted activity of NF-M, a nuclear factor that binds to a C/EBP motif

In a search for monocyte-specific nuclear factors, we analyzed in human cells the promoter of the chicken myelomonocytic growth factor, a gene that, in the chicken, is expressed in myeloid and myelomonocytic cells. Reporter gene constructs were active in monocytic Mono Mac 6 cells and in monoblastic THP-1 cells but not in the hematopoietic stem cell line K562. When a region with homology to the sequence recognized by CAAT enhancer-binding proteins (C/EBP) was inactivated by site-directed mutagenesis, the reporter activity was reduced by a factor of 10. Multimers of this region, termed F, in front of a heterologous promoter were active in Mono Mac 6 and THP-1 cells but not in K562 cells, WIL2 B cells, BT20 mammary carcinoma cells, MelJuso melanoma cells, or SK-Hep-1 hepatoma cells. Gel shift analysis with the F oligonucleotide identified DNA-binding activity in monocytic Mono Mac 6, monoblastic THP-1, and myelomonocytic HL60 cells. No binding was detected in myelomonocytic RC2A cells, in myeloid KG-1 cells, or in the hematopoietic stem cell line K562. Furthermore, a panel of solid tumor cell lines, representing various tissues, were also negative. Stimulation by PMA could not induce this binding factor in any of the negative cell lines. Analysis of primary cells (granulocytes, T cells, monocytes, and alveolar macrophages) revealed binding activity only in monocytes and macrophages. This DNA-binding factor, termed NF-M, was found to consist of two molecules, of 50 and 72 kDa, as determined by affinity cross-linking. Binding of NF-M was competed by the region F oligonucleotide and by the C/EBP motif from the albumin enhancer but not by an AP-2 motif. These data suggest that NF-M is a member of the C/EBP family of nuclear factors. The monocyte-restricted activity of NF-M suggests that this nuclear factor may be involved in regulation of monocyte-specific genes.

Constitutive monocyte-restricted activity of NF-M, a nuclear factor that binds to a C/EBP motif

In a search for monocyte-specific nuclear factors, we analyzed in human cells the promoter of the chicken myelomonocytic growth factor, a gene that, in the chicken, is expressed in myeloid and myelomonocytic cells. Reporter gene constructs were active in monocytic Mono Mac 6 cells and in monoblastic THP-1 cells but not in the hematopoietic stem cell line K562. When a region with homology to the sequence recognized by CAAT enhancer-binding proteins (C/EBP) was inactivated by site-directed mutagenesis, the reporter activity was reduced by a factor of 10. Multimers of this region, termed F, in front of a heterologous promoter were active in Mono Mac 6 and THP-1 cells but not in K562 cells, WIL2 B cells, BT20 mammary carcinoma cells, MelJuso melanoma cells, or SK-Hep-1 hepatoma cells. Gel shift analysis with the F oligonucleotide identified DNA-binding activity in monocytic Mono Mac 6, monoblastic THP-1, and myelomonocytic HL60 cells. No binding was detected in myelomonocytic RC2A cells, in myeloid KG-1 cells, or in the hematopoietic stem cell line K562. Furthermore, a panel of solid tumor cell lines, representing various tissues, were also negative. Stimulation by PMA could not induce this binding factor in any of the negative cell lines. Analysis of primary cells (granulocytes, T cells, monocytes, and alveolar macrophages) revealed binding activity only in monocytes and macrophages. This DNA-binding factor, termed NF-M, was found to consist of two molecules, of 50 and 72 kDa, as determined by affinity cross-linking. Binding of NF-M was competed by the region F oligonucleotide and by the C/EBP motif from the albumin enhancer but not by an AP-2 motif. These data suggest that NF-M is a member of the C/EBP family of nuclear factors. The monocyte-restricted activity of NF-M suggests that this nuclear factor may be involved in regulation of monocyte-specific genes.

Gangliosides suppress tumor necrosis factor production in human monocytes

Both normal and malignant cells contain gangliosides as important cell membrane constituents that, after being shed, may influence cells of the immune system. We have studied the impact of gangliosides on the expression of TNF in blood monocytes and in the monocytic cell line Mono Mac 6. Although under standard culture conditions, bovine brain gangliosides (100 micrograms/ml) suppressed LPS-stimulated TNF production 5-fold in PBMC and 10-fold in Mono Mac 6 cells, suppression was more efficient under serum-free conditions. Looking at highly purified gangliosides, GD3, GD1a, GM3, GM2, and GM1 were all effective in reducing TNF production in PBMC, and in Mono Mac 6 by factor 10 to 50. The suppressive activity was lost in molecules, lacking the sugar moiety or the lipid moiety. Gangliosides appear to act at an early step of activation in that TNF transcripts were reduced and the mobilization of the nuclear factor kappa B was blocked. Furthermore, in time kinetics, gangliosides were effective for up to 30 min after addition of LPS, but not thereafter. However, the expression of the CD14 Ag, a receptor molecule for LPS-LPS binding protein complexes, was unaffected by gangliosides. Finally, when using Staphylococcus aureus or platelet activating factor as a stimulus, gangliosides were able to suppress TNF production in Mono Mac 6 cells by factor 5 to 10, as well. On the other hand, phorbol ester-induced production of O2- was similar in cells treated with and without gangliosides. Taken together, our data demonstrate that TNF gene expression in monocytes induced by different types of stimuli can be blocked by gangliosides at an early step of signal transduction.

Gangliosides suppress tumor necrosis factor production in human monocytes

Both normal and malignant cells contain gangliosides as important cell membrane constituents that, after being shed, may influence cells of the immune system. We have studied the impact of gangliosides on the expression of TNF in blood monocytes and in the monocytic cell line Mono Mac 6. Although under standard culture conditions, bovine brain gangliosides (100 micrograms/ml) suppressed LPS-stimulated TNF production 5-fold in PBMC and 10-fold in Mono Mac 6 cells, suppression was more efficient under serum-free conditions. Looking at highly purified gangliosides, GD3, GD1a, GM3, GM2, and GM1 were all effective in reducing TNF production in PBMC, and in Mono Mac 6 by factor 10 to 50. The suppressive activity was lost in molecules, lacking the sugar moiety or the lipid moiety. Gangliosides appear to act at an early step of activation in that TNF transcripts were reduced and the mobilization of the nuclear factor kappa B was blocked. Furthermore, in time kinetics, gangliosides were effective for up to 30 min after addition of LPS, but not thereafter. However, the expression of the CD14 Ag, a receptor molecule for LPS-LPS binding protein complexes, was unaffected by gangliosides. Finally, when using Staphylococcus aureus or platelet activating factor as a stimulus, gangliosides were able to suppress TNF production in Mono Mac 6 cells by factor 5 to 10, as well. On the other hand, phorbol ester-induced production of O2- was similar in cells treated with and without gangliosides. Taken together, our data demonstrate that TNF gene expression in monocytes induced by different types of stimuli can be blocked by gangliosides at an early step of signal transduction.

In vitro desensitization to lipopolysaccharide suppresses tumour necrosis factor, interleukin-1 and interleukin-6 gene expression in a similar fashion

Like blood monocytes, the human monocytic cell line Mono Mac 6 can be stimulated by lipopolysaccharide (LPS) at 1 microgram/ml to produce high levels of cytokines. When Mono Mac 6 cells are stimulated for 4-6 hr at 1 x 10(6)/ml, supernatants contain tumour necrosis factor (TNF) at an average of 60 U/ml and interleukin-6 (IL-6) at an average of 1000 U/ml. IL-1 is not detected in the supernatant, but after three freeze-thaw cycles cell-associated IL-1 can be detected (100 U/ml) and with similar amounts of IL-alpha and -beta. Preculture of Mono Mac 6 cells with LPS at 10 ng/ml for 3 days results in cells refractory to subsequent stimulation by LPS at 1 microgram/ml. In the refractory desensitized cells, production of all three cytokines is down-regulated, with a more than 10-fold reduction in protein production. For all three cytokines, this desensitization appears to be regulated at the transcript level, with a strong reduction in specific mRNA as detected by Northern blot analysis. Furthermore, Mono Mac 6 cells can be stimulated by Staphylococcus aureus (LPS contamination less than 10 pg/ml) to produce cytokines. This type of stimulus is unable to overcome desensitization, in that the secretion of TNF in LPS-precultured Mono Mac 6 cells was 10- to 100-fold lower than in Mono Mac 6 cells without LPS preculture. These data show that desensitization in Mono Mac 6 cells affects all three cytokines tested and that it extends to other activating signals, such as staphylococci.

Differential expression of cytokines in human blood monocyte subpopulations

Cytokine expression was analyzed in CD14++ regular monocytes and in the novel subset of CD14+/CD16+ small monocytes. Biologic activity for tumor necrosis factor (TNF), interleukin-1 (IL-1), and IL-6 in the supernatant of elutriator-enriched, cell sorter-purified small monocytes was about 10-fold lower compared with regular monocytes when stimulated with lipopolysaccharide (LPS) for 12 hours. In CD14++ regular monocytes levels were 1,157 U x 10(-3)/mL, 158 U/mL, and 1,337 U/mL for TNF, IL-1, and IL-6, respectively. By contrast, CD14+/CD16+ small monocytes exhibited 137 U x 10(-3)/mL, 14 U/mL, and 60 U/mL for TNF, IL-1, and IL-6, respectively. Additional treatment with interferon-gamma enhanced production of TNF in both subsets, but CD14+/CD16+ small monocytes still exhibited lower levels. Stimulation of the monocyte subsets by platelet-activating factor gave the same pattern of results. Hybridization with 32P-labeled oligonucleotides specific for the respective cytokine messenger RNAs (mRNAs) showed a 10-fold lower prevalence of transcripts for TNF, IL-1, and IL-6, as well. By contrast, the constitutive expression of Glyceraldehyde-3-phosphate-dehydrogenase mRNA was 1.7-fold higher in the CD14+/CD16+ small monocytes. These data indicate that the novel subset of small monocytes is selectively suppressed in the expression of the cytokines TNF, IL-1, and IL-6, suggesting that these cells may comprise a deactivated type of cell. The expression of class II transcripts in the small monocytes is, however, similar to the regular monocytes, and the cell surface expression of class II protein about threefold increased. Thus, the novel subset of small monocytes appears to be a functionally distinct type of cell.

Small (CD14+/CD16+) monocytes and regular monocytes in human blood

Compared to the obvious phenotypic and functional heterogeneity of tissue macrophages, little information is available on subsets of blood monocytes. We have employed two-color immunofluorescence and flow cytometry for the definition of regular and small monocytes, the latter characterized by the low-density expression of CD14 and the strong expression of the CD16 (Fcy-RIII) antigen. These cells comprise 15% of the blood monocytes and they appear to be similar in phenotype to the alveolar macrophage. The CD14+/CD16+ small monocytes can perform phagocytosis and they produce reactive oxygen, while their capacity for cytokine production is strongly reduced when compared to regular monocytes. At this point it is still unclear as to whether the CD14+/CD16+ small monocytes comprise a specific level of activation or differentiation or a distinct sublineage of human blood monocytes.

Molecular mechanisms in down-regulation of tumor necrosis factor expression

Excessive production of tumor necrosis factor (TNF) after stimulation by lipopolysaccharide (LPS) may result in fever, intravascular coagulation, and lethal shock. An efficient way of preventing the excessive TNF production is desensitization of monocytes/macrophages to LPS. We have analyzed the molecular mechanisms involved in the induction of desensitization and the mechanisms operative in the desensitized, LPS-refractory cells by employing the human monocytic cell line Mono-Mac-6. Similar to human blood monocytes, treatment of Mono-Mac-6 cells with LPS (1 microgram/ml) results in a rapid and transient expression of TNF. When Mono-Mac-6 cells are precultured in medium containing low levels of LPS, they become refractory to subsequent LPS stimulation and show no or little secretion of TNF protein. Desensitization can be blocked by the inhibition of cyclooxygenase and protein kinase C; both prostaglandin E2 (together with a second signal) and phorbol 12-myristate 13-acetate can mimic desensitization. By employing prostaglandin E2 and low concentrations of phorbol 12-myristate 13-acetate, a synergism in the induction of desensitization can be demonstrated. Hence, our studies show that two distinct pathways are involved in the induction of hyporesponsiveness. In both LPS-responsive and LPS-desensitized Mono-Mac-6 cells, LPS was able to induce the transcription factor NF-kappa B in the nucleus. Still, the prevalence of TNF-specific mRNA was dramatically reduced in the desensitized cells. These data indicate that LPS-desensitized Mono-Mac-6 cells are able to activate initial steps of signal transduction up to the level of the NF-kappa B transcription factor. The absence of TNF transcripts, however, indicates that additional nuclear factors may be missing or that silencers may be active such that transcription of the TNF gene is prevented.

Infection of the human monocytic cell line Mono Mac6 with human immunodeficiency virus types 1 and 2 results in long-term production of virus variants with increased cytopathogenicity for CD4+ T cells

The recently established human monocytic cell line Mono Mac6 expressing distinct characteristics of mature monocytes/macrophages was tested for its susceptibility to infection with human immunodeficiency virus. Inoculation of the cells with the T-cell-tropic human immunodeficiency virus strains human T-lymphotropic virus type IIIB and lymphadenopathy-associated virus type 2 led to a noncytopathic productive infection becoming apparent only after a latency period of up to 56 days. The infectibility of the Mono Mac6 cells was dependent on low levels of CD4 expression, as demonstrated by blocking experiments with various CD4-specific antibodies. Increasing with time after infection (greater than 200 days), the cultured Mono Mac6 cells released virus variants which showed shortened latency periods when passaged onto uninfected Mono Mac6 cells. Also, cytopathogenicity for several CD4+ T cells of the Mono Mac6-derived virus was drastically increased; thus, the infection of the H9 cell line with low doses of virus (less than 0.1 50% tissue culture infective dose per cell) led to giant syncytium formation within 1 day and subsequent death of all fused cells. We propose Mono Mac6 cells as a new model for the study of human immunodeficiency virus infecting the monocyte/macrophage lineage, particularly with regard to virus-host cell interaction and the influence of cell differentiation and activation on latency and development of virulence. The human immunodeficiency virus-infected Mono Mac6 cell may also serve as a valuable tool for in vitro testing of antiviral therapies.

Conservative treatment of ectopic pregnancy with local injection of hyperosmolar glucose solution or prostaglandin-F2 alpha: a prospective randomised study

In a prospective randomised study, 31 patients with an unruptured tubal pregnancy were treated either with local and systemic prostaglandins or with local instillation of a hyperosmolar glucose solution. Prostaglandin therapy was successful in 13 of 15 patients and glucose therapy in 16 of 16. 9 women treated with prostaglandins had cramping abdominal pains postoperatively. No side-effects were noted in those treated with glucose. At subsequent hysterosalpingography 5 of 6 patients treated with prostaglandins and 7 of 8 treated with glucose had normal tubal configuration and patency. 3 patients treated with glucose later had a normal intrauterine pregnancy, demonstrably through the affected tube in 1 case. These results suggest that local instillation of hyperosmolar glucose solution is an option in the laparoscopic management of unruptured tubal pregnancies.

Inhibition of lipopolysaccharide-induced in vitro desensitization by interferon-gamma

Exposure of Mono-Mac-6 cells to lipopolysaccharide (LPS) can induce rapid and transient expression of cytokines like tumor necrosis factor (TNF), interleukin 1 and interleukin 6. Preculture of Mono-Mac-6 cells in culture medium containing small amounts (1-50 ng/ml) of LPS for 3 days leads to an unresponsiveness to a subsequent stimulation with a high amount of LPS. This in vitro desensitization of a monocytic cell line may serve as a model for desensitization to LPS seen in vivo, for example in mice or man repetitively treated with LPS. Addition of interferon-gamma (IFN-gamma) to the Mono-Mac-6 cells during the LPS preculture period leads to an inhibition of desensitization, whereas addition of IFN-alpha or IFN-beta is not able to inhibit the LPS-induced desensitization. The inhibition of desensitization by IFN-gamma was dose dependent and time dependent. Preculture of Mono-Mac-6 cells with LPS leads to a strong reduction of TNF mRNA. This reduction of specific mRNA is also overcome by addition of IFN-gamma, but not by IFN-alpha and IFN-beta, indicating that pretranslational mechanisms are responsible for the regulation of TNF in desensitization.

Downregulation of tumor necrosis factor expression in the human Mono-Mac-6 cell line by lipopolysaccharide

Mono-Mac-6 cells, but not U937 cells, can be induced to rapidly express tumor necrosis factor (TNF) mRNA and protein when triggered with lipopolysaccharide (LPS) at 1 microgram/ml. Preincubation of the cells for 3 d with low amounts of LPS (10 ng/ml) results in nearly complete suppression of TNF secretion. This downregulation appears to occur at the pretranslational level since specific mRNA is virtually undetectable under these conditions. By contrast, the same preincubation with 10 ng/ml LPS results in enhanced phagocytosis (28.6-67.2% for Staphylococcus aureus), demonstrating that not all monocyte functions are suppressed. While these results show that only stringent exclusion of LPS from culture media allows for induction of TNF in the Mono-Mac-6 cell line, the pronounced effect of LPS preincubation may also provide a suitable model with which to study the mechanisms of LPS-induced desensitization.

Fetal outcome in gestational diabetes with elevated amniotic fluid insulin levels. Dietary versus insulin treatment

Of 228 women with gestational diabetes between 28 and 32 gestational weeks, 195 had a normal amniotic fluid insulin level (4.8 +/- 3.6 microU/ml) while 33 (14.5%) had an elevated level (23.1 +/- 10 microU/ml). Women with a normal amniotic fluid insulin level were treated by diet alone. Fourteen of the women with an elevated level were treated by diet alone; 19 received insulin treatment additionally. The fetal outcome of patients with a normal amniotic fluid insulin level and dietary therapy and of those with an elevated level and insulin treatment was similar to that of metabolically healthy women. The newborns of gestational diabetics with elevated amniotic fluid insulin treated by diet alone showed a significantly higher incidence of neonatal hyperinsulinism, hypoglycemia, hyperbilirubinemia, high birth weight, respiratory distress syndrome and hypocalcemia. While 2/14 (14%) of the neonates in the dietary group had fatal respiratory distress syndrome, there were no deaths in the group with elevated amniotic fluid insulin and insulin treatment. The data demonstrate that in gestational diabetics with normal amniotic fluid insulin (low-risk group), dietary therapy is sufficient while insulin therapy is required to ensure healthy offspring in patients with elevated amniotic insulin (high-risk group).

Monocyte phenotype and function in patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related disorders

The CD4 molecule, which is known to play an important role in the susceptibility of T lymphocytes to infection by the human immunodeficiency virus (HIV), is also expressed in small amounts on the surface of monocytes. Since monocytes can also be infected by the virus, we investigated peripheral blood monocytes of patients with the acquired immunodeficiency syndrome (AIDS), AIDS-related complex (ARC), and HIV seropositive and seronegative haemophiliacs without symptoms for the expression of the CD4 molecule and for other functionally important surface molecules such as CD11 (C3bi receptor), transferrin receptor, Fc receptor, and the three major histocompatibility complex (MHC) class II antigens HLA-DP, HLA-DR, and HLA-DQ. With immunofluorescence staining and flow cytometry no difference was found between patients and controls for the expression of the CD4 molecule and for the other antigens as assessed by the percentage of positive staining and the specific fluorescence intensity in a double marker analysis. The percentage of CD4+ monocytes was found to be 59.2 +/- 14.4% for 16 patients with AIDS and 52.9 +/- 12.8% for 12 healthy controls. Similar to our results on phenotype, we found no significant difference with respect to the production of tumour necrosis factor (TNF), in that monocytes of AIDS and ARC patients showed an increase in TNF secretion after stimulation with LPS comparable to controls.

Tumor necrosis factor as effector molecule in monocyte mediated cytotoxicity

A newly developed assay system which uses actinomycin D (Act D) pretreated Wehi 164 target cells allows for the measurement of human monocyte cytotoxicity in a 7-h 51Cr release assay. Using the monocyte specific monoclonal antibody M42 in a direct rosetting procedure we confirm herein that among human peripheral blood mononuclear cells cytotoxicity is restricted to monocytes. When applying stringent conditions that exclude exogenous lipopolysaccharide (LPS) we could demonstrate that as little as 0.1 ng of LPS per ml triggers this cytotoxicity. Further, a factor can be detected in supernatants of mononuclear cells which is also cytotoxic against Act D treated Wehi 164 cells. This cytotoxic factor can be triggered by LPS within 4 h, but at as low a LPS concentration as 0.001 ng/ml. Since one of the LPS triggered monocyte products is tumor necrosis factor (TNF), we tested the effect of recombinant TNF cloned from the U937 cell line and we could show potent lytic activity against Act D pretreated but not, or only minimally, against untreated Wehi 164 target cells. Recombinant TNF rapidly lysed the target with significant specific release occurring as early as after 3 h in the assay. By contrast, recombinant interleukin 1 gave no lysis while lymphotoxin derived from the RPMI 1788 cell line was effective. An affinity purified antiserum directed against TNF neutralized the lytic activity of recombinant TNF and also the cytotoxic factor produced by LPS triggered mononuclear cells, while the antiserum was ineffective against lymphotoxin. Further, the antiserum when added to the assay of effector cells and Act D treated Wehi 164 cells also completely ablated cytotoxic activity. Size fractionation of cytotoxic factor and recombinant TNF by high pressure liquid chromatography led to a superimposable peak of cytotoxicity in the molecular weight range of 9,500-17,000. Further, immunoblotting with the anti-TNF antibody revealed the same Mr 15,500-16,500 band for the recombinant TNF and LPS triggered cytotoxic factor. Taken together, our data demonstrate that the cytotoxic activity of human monocytes against Act D treated Wehi 164 is mediated entirely by a LPS triggered molecule that is very similar or identical to the human tumor necrosis factor. The assay system thus provides a powerful tool to analyze the biology of TNF in humans.

Continuous insulin delivery systems for the pregnant diabetic patient

In highly unstable diabetes (brittle diabetes) the degree of metabolic control called for today in managing the pregnant diabetic patient is not achievable by intensified conventional insulin therapy. These cases have been markedly improved by continuous insulin delivery systems. In the course of 2 years, 6 diabetic pregnant patients (8%) were treated with insulin pumps for a total of 910 days, using the intravenous route once, the intraperitoneal route twice and the subcutaneous route three times. The group consisted of one White C, one White D and four White R diabetic patients. Metabolic control was achieved by 5,916 blood sugar measurements, 42 determinations of glycosylated hemoglobin (HbA1) and 19 determinations of amniotic fluid insulin. The intravenous and the subcutaneous route showed about the same rate of hypoglycemia as intensified conventional insulin therapy. Hypoglycemia did not appear, however, under intraperitoneal insulin administration. Mean blood glucose in patients on the pump dropped from 121.0 to 97.4 mg/dl. The standard deviation of the blood glucose values during one week dropped from 64.5 to 35.2 mg/dl, the mean amplitude of glycemic excursions (MAGE) from 100 to 43 mg/dl and the mean of daily differences (MODD) from 72 to 29 mg/dl. The concentration of glycosylated hemoglobin sank from 10.5 to 6.8%. The metabolic condition improved significantly. On average, the patients were hospitalized for 7.5 (1.7-12.8) weeks. Fetal hyperinsulinism developed in 2 patients on the pump and was reversible by closer metabolic management. Neonatal weight was in the normal range and there were no signs of diabetogenic fetopathy.