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Biomedical subjects

M Peakman

Publications and source records attributed to M Peakman.

At least 55 records · Page 3Linked to original sources
PubMed1996

Peripheral blood and intrahepatic subsets of T lymphocyte activation and function in liver allograft rejection and drug-induced tolerance in rats.

T lymphocyte kinetics in liver allograft rejection were studied by measuring levels of activated (CD25+ and class II MHC+) T lymphocytes (CD5+) and T cell subsets (CD4 and CD8) in peripheral blood and the livers of allogeneic DA (RT1b) to LEW (RT1') and syngeneic LEW to LEW orthotopic rat liver transplants. Median survival was 10 days in untreated allogeneic rats (n = 17). Mean (+/- SEM) T lymphocyte class II MHC expression increased from 3.4 +/- 0.44% (day 2/3) to 4.9 +/- 1.1% (day 7) (p = 0.01). Complete sequential data were available for nine animals over the period of rejection confirming the increase in class II MHC expression (p = 0.05) and showing a decrease in CD25 expression (p = 0.05). There was a significant fall in CD4:CD8 ratio from day 2/3 to day 7 (p = 0.002). CD25 and class II MHC molecule expression and the CD4:CD8 ratio remained unchanged over the comparable period in the syngeneic LEW to LEW control model (n = 5, p > 0.3 for all comparisons). Cyclosporin A (5 mg/kg/day) was given orally for 17 days and then withdrawn to induce allograft tolerance in a further nine DA to LEW rats (median survival > 100 days). Samples taken at 2/3, 7, 17, 30, 40 and 100 days showed that T cell activation marker expression remained low during cyclosporin treatment (e.g. class II MHC expression 2.32 +/- 0.35%; CD25 expression 3.53 +/- 0.44% on day 7) but increased thereafter (e.g. class II MHC expression 8.19 +/- 0.65%. CD25 13.25 +/- 0.95% on day 100). There was a fall in CD4:CD8 ratio throughout (p < 0.001). Intrahepatic mononuclear cells were harvested from six normal livers, four allogeneic livers (at 10 days), five syngeneic livers (at 10 days) and five tolerant allografts (at 100 days). Rejecting grafts showed the highest proportion of T lymphocytes (66.8 +/- 4.0% vs 18.5 +/- 3.6% in controls, p = 0.01). T cell activation was higher in both rejecting and tolerant grafts versus normal control livers (p = 0.05 for CD25 and p < 0.01 for class II MHC expression). CD8+ lymphocytes predominated in the hepatic infiltrate in all models, although the majority of these cells were both CD5 and alpha beta T cell receptor negative. There was a higher proportion of T cells in tolerant allografts (44.5 +/- 5.2%, p < 0.01) compared with control animals. Serial changes in peripheral T lymphocyte subsets may be useful in monitoring experimental acute rejection. In peripheral blood, the increase in T cell activation and loss of CD4+ lymphocytes, along with evidence of increased intragraft infiltration by this subset implies that it has a primary role in the development of tolerance in this nodel.

Animals↗
PubMed1996

The influence of capsulation and lipooligosaccharide structure on neutrophil adhesion molecule expression and endothelial injury by Neisseria meningitidis.

Host inflammatory response to meningococcal infection is believed to be a major determinant of disease severity. Isogenic mutants of Neisseria meningitidis serogroup B1940, which differ in expression of capsular polysaccharide and lipooligosaccharide (LOS), were used to examine host responses in a whole blood model of bacteremia and a model of endothelial injury. The parent organism caused significantly less neutrophil shedding of the adhesion molecule, L-selectin, than the three mutant organisms (P < .01) and was most resistant to the bactericidal activity of whole blood. Despite marked differences in bacterial adhesion to endothelial cells (P < .05), no damage was induced by organisms alone. Endothelial injury was observed when neutrophils were incubated with adherent, capsule-deficient organisms (P < .05). The degree of endothelial damage was related to the number of neutrophils adherent to the endothelium. Thus, bacterial capsulation and LOS structure can influence neutrophil activation and endothelial injury and, as such, may be important in the pathogenesis of meningococcal sepsis.

Antigens, Bacterial↗
PubMed1996

Identification of 3 beta-hydroxysteroid dehydrogenase as a novel target of steroid cell autoantibodies: association of autoantibodies with endocrine autoimmune disease.

Autoantibodies directed against steroid hormone-producing cells (SCA) detectable by immunofluorescence are typically found in a small proportion of patients with premature ovarian failure (POF) as well as in other endocrine autoimmune diseases. The SCA pattern stains cells in the outer zones of the adrenal cortex, ovary, and testis. To identify the molecular target of SCA, an adrenal complementary DNA expression library was screened using SCA-positive serum, and the steroid enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) was identified. Only 1 of 48 (2%) patients with idiopathic POF, not pre-selected for the presence of other autoimmune diseases, had SCA by immunofluorescence, whereas 10 of 48 (21%) had anti-3 beta HSD autoantibodies detectable by immunoblot using recombinant human enzyme compared with 6 of 115 (5%) control subjects (P = 0.002). Absorption of SCA-positive serum with recombinant human 3 beta HSD abolished the immunofluorescence pattern. We also examined the prevalence of anti-3 beta HSD autoantibodies in other endocrine autoimmune diseases. Two of 112 (2%) diabetic patients, but none of the thyroid or Addisonian patients, had SCA by immunofluorescence. Twenty-six (23%) diabetic subjects (P < 0.001 vs. controls), 3 of 18 thyroid patients (P > 0.05 vs. controls), and none of 4 Addisonian patients had anti-3 beta HSD autoantibodies. 3 beta HSD is the first steroid cell autoantigen defined at the molecular level to be associated with idiopathic POF occurring in the absence of other polyglandular diseases. Autoantibodies to 3 beta HSD in patients with other organ-specific autoimmune diseases indicate that the enzyme behaves as a typical target of polyendocrine autoimmunity. Anti-3 beta HSD autoantibodies in patients with POF may provide a marker of those subjects whose ovarian failure is autoimmune in origin and, as recent studies suggest, may be salvageable with glucocorticoid treatment.

3-Hydroxysteroid Dehydrogenases↗
PubMed1996

Persistent activation of CD8+ T-cells characterizes prediabetic twins.

OBJECTIVE: Elevated circulating levels of activated CD3+ T-cells are characteristic of type I diabetes at diagnosis, and activated CD8+ (cytotoxic/suppressor) T-cells predominate in the islet infiltrate. The aim of this study was to examine the peripheral blood of prediabetic and nondiabetic identical twins of patients with type I diabetes for the presence of activated CD8+ T-cells and by comparing these groups, analyze the relationship of such cells to the development of the disease. RESEARCH DESIGN AND METHODS: In a 10-year prospective study, blood T-cell subsets (CD3+ total T-cells, CD4+ helper/inducer, and CD8+ cytotoxic/suppressor) were analyzed for evidence of activation (cell surface expression of HLA-DR, CD25) in 18 identical twins of patients with type I diabetes, 8 of whom became diabetic (prediabetic twins), while 10 remained nondiabetic after at least 8 years of follow-up and are now at low risk for type I diabetes. Fifteen healthy individuals were studied as control subjects. RESULTS: At the beginning and during the study, percentage levels of activated CD3+ HLA-DR+ T-cells were significantly elevated in prediabetic and low-risk twins compared with control subjects (P < 0.005) but remained high only in prediabetic twins (P < 0.005). Both prediabetic and low-risk twins had elevated levels of HLA-DR+ CD4+ T helper cells compared with control subjects throughout the study (P < 0.001), and these remained high in both (P < 0.001 and P < 0.05, respectively). Only prediabetic twins had elevated levels of HLA-DR+ CD8+ T-cells during the study. These were significantly higher than in control subjects (P < 0.005) and low-risk twins (P < 0.05) and remained persistently elevated to diagnosis (P < 0.001). Abnormally elevated levels of HLA-DR+ CD8+ T-cells in twins indicate a 50% risk of progression to type I diabetes by life-table analysis (P = 0.01), with a positive predictive value of 100%, sensitivity of 50%, and specificity of 100%. Elevated CD25+ T-cell levels in prediabetic and low-risk twins were less marked and less able to discriminate between the twin groups. CONCLUSIONS: These results demonstrate that prediabetes is characterized by persistent elevation of HLA-DR+ CD8+ T-cells with the same cytotoxic phenotype as cells predominating in the islet at diagnosis, suggesting that the circulating cells may have a role in the pathogenesis of islet damage.

Adolescent↗
PubMed1995

FK506 in liver transplantation for chronic hepatitis B: in vitro studies on lymphocyte activation and virus replication.

Recurrence of hepatitis B virus (HBV) in the graft is the major problem for patients with chronic HBV infection undergoing liver transplantation, which could be potentiated by the immunosuppression. In the present study, we used lymphocytes and hepatocytes isolated from patients with chronic HBV infection to investigate in vitro the effects of FK506 with and without methylprednisolone (25 ng/mL) on mitogen-induced lymphocyte proliferation, T-cell activation marker expression, and HBV replication in human hepatocytes. Increasing concentrations of FK506 (0.1, 0.5, and 5 ng/mL) resulted in a dose-dependent inhibition of lymphocyte proliferation with a reduction of the stimulation index by 9.2%, 39.0%, and 55.1%, respectively, with no difference between 25 chronic HBV carriers and normal controls. Methylprednisolone alone had no effect but potentiated the inhibitory effect of all three FK506 concentrations, such that the stimulation index was decreased by 20%, 56.2%, and 65.7%, respectively. FK506 (0.5 ng/ mL) reduced both the percentage of interleukin-2 receptor expressing T cells and the cell surface density of this receptor by 7.1% and 8.7% (P < .01), whereas it only reduced the proportion of HLA-DR expressing T cells by 6.8%. FK506 did not change significantly the intracellular HBV DNA or the hepatic expression of hepatitis B surface antigen (HBsAg) in short-term culture of human hepatocytes, whereas methylprednisolone increased the percentage of HBsAg-positive hepatocytes in all 5 patients with active viral replication. These results indicate that the effects of FK506 on T-cell activation in chronic HBV carriers are identical to normal subjects, resulting in marked suppression of T-lymphocyte function but only modest reduction in the expression of cell surface activation markers. The drug showed no direct stimulatory effect on viral replication, suggesting that FK506 can be a useful, steroid-sparing immunosuppressive agent for liver graft recipients with chronic HBV infection.

Adult↗
PubMed1995

Markers of immune cell activation and disease progression. Cell activation in HIV disease.

Immune cell activation is a feature of infection with the human immunodeficiency virus (HIV). Here we report our studies on a cohort of over 400 patients with HIV infection studied cross-sectionally and longitudinally to examine the relationship between markers of immune cell activation and disease progression. To examine disease progression, 340 patients with HIV infection but without AIDS were followed for a total of 574 patient years, during which 56 developed AIDS. In our first study, 157 patients in CDC groups II-IV were examined cross-sectionally for in vivo expression of the activation markers HLA-DR and CD25 on CD3, CD4 and CD8 T cells. Levels of CD3+ HLA-DR+ T cells are high in HIV infection and show a significant negative correlation with CD4 counts (r = 0.52; p < 0.001). The appearance of HLA-DR+ CD3+ T cells is an early feature of asymptomatic HIV+ patients, with a greater proportion (82%) showing abnormally high levels of these than abnormally low levels of CD4 (52%; p < 0.001). Examining activation of the CD4 subset specifically is likely to be of greater interest, given that this cell is the viral target. Indeed, we found that in the cross-sectional study, levels of HLA-DR+ and CD25+ CD4 lymphocytes show a step-wise linear increase with increasing disease severity (significant test for linear trend; p < 0.001). In our previous studies, only declining CD4 count has shown such a significant linear trend. These data suggest that measuring activated CD4+ T cells in the periphery may be a powerful predictive tool. In our second study, we examined the expression of other markers acquired (CD45R0) and lost (CD45RA) following activation of naïve T cells. Examining expression of these on CD4 and CD8 cells cross-sectionally in 71 HIV+ patients, we found abnormalities in percentage levels of CD45RA+ and CD45R0+ populations, none of which showed any relationship to disease severity. Intriguingly, however, we noted that the surface density of both CD45RA and CD45R0 molecules on CD4 and CD8 cells was markedly and significantly reduced at all stages of HIV infection (eg relative specific fluorescence reduced by up to 50%; p < 0.001). This abnormality was confirmed in studies using antibodies to a common epitope on all CD45 isoforms (pan-CD45) and to the CD45RB isoform. Finally, returning to the question of immune cell markers of activation and disease progression, we have examined some of the best documented markers in our longitudinal study.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1995

The effects of islet cell surface antibodies on the metabolic function of mouse islet B cells in vitro.

Immunoglobulin (Ig) fractions from the plasma of a group of newly diagnosed insulin-dependent diabetes mellitus (type 1) patients and set of control subjects were assessed for their effects on isolated mouse islet function. It was found that Igs from type 1 patients caused a significant inhibitory effect on insulin secretion when incubated with mouse islets as compared with controls (25.6 +/- 2.9 pg islet-1 h-1 vs 44.7 +/- 7.7 pg islet-1 h-1, P < 0.05). The plasma samples from which the Igs were obtained were then tested for the presence of antibodies to the mouse islet cell surface (ICSA). Four of the nine patients were positive for ICSA, and plasma samples from eight control subjects were all negative. ICSA-positive samples appeared to have the greatest inhibitory effect on insulin secretion when compared with their respective controls (53.3 +/- 7.0 pg insulin islet -1 min-1 vs 30.9 +/- 3.7 pg insulin islet -1 min-1, (P < 0.05). In contrast, it was also found that ICSA-positive Ig fractions had no significant effect on glucose oxidation when co-incubated with mouse islets as compared with the controls (11.3 +/- 2.3 pmol islet-1 h-1 vs 11.2 +/- 2.9 pmol islet-1 h-1). These studies suggest that Igs from newly diagnosed type 1 patients containing ICSA may impair insulin secretion from isolated mouse islets by mechanisms which do not involve the inhibition of B-cell glucose metabolism.

Adolescent↗
PubMed1995

Circulating levels of mannose binding protein in human immunodeficiency virus infection.

Mannose binding protein (MBP) is a serum lectin which, upon binding to a carbohydrate extremity, acquires the ability to activate the classical complement pathway. MBP binds human immunodeficiency virus (HIV) in vitro via glycans on gp120 and thus, it may play a defensive role in HIV infection and contribute to virus clearance through the activation of complement associated with this condition. We measured serum MBP and activation indices of the classical complement pathway (plasma C4d and C3d) in HIV-seropositive patients at different stages of disease severity, and in normal subjects. MBP was higher in HIV patients as a whole and in each Centers for Disease Control (CDC) group than controls (P<0.01). MBP was not significantly different between CDC groups and and did not significantly correlate either with CD4-positive lymphocytes, neopterin or beta2-microglobulin or with C4d and C3d. The possibility that MBP plays a defensive role in HIV infection cannot be excluded, but, it it is, it does not appear to act by recruiting complement for vital elimination.

Adult↗
PubMed1995

Whole blood model of meningococcal bacteraemia--a method for exploring host-bacterial interactions.

An ex vivo whole blood model of meningococcal bacteraemia was developed to examine the total bactericidal activity of blood. Using a single defined donor and strains belonging to serogroups A, B and C and an unencapsulated strain, we demonstrated that the bactericidal mechanisms operating in whole blood varied with anticoagulant, serogroup and bacterial growth conditions. The choice of anticoagulant had a major effect on the survival of the serogroup A strain with 94% (SEM 7.6) survival in citrated blood compared to 19.7% (SEM 19.6) survival in heparinised blood after 60 min incubation. The serogroup C strain showed enhanced survival when grown in liquid medium compared to growth on solid medium (73.5%, SEM 7.5, and 8.2%, SEM 3.1, respectively, in citrated blood after 60 min). The pattern of survival of serogroup B and the unencapsulated strain were largely unaffected by these variables. Comparison with cell free conditions allowed the contribution of cellular components in meningococcal killing to be determined. Secreted levels of tumour necrosis factor and neutrophil elastase secreted during whole blood assays did not correlate with bacterial growth or viability indicating a lack of relationship between killing and activation of phagocytes.

Anticoagulants↗
PubMed1995

Cell cycling in HIV infection: analysis of in vivo activated lymphocytes.

Infection with HIV results in increased circulating levels of T lymphocytes expressing phenotypic markers of immune activation. In the present study, using three-colour immunofluorescence, we examined the cell cycle status of these activated cells. Activated (HLA-DR+, CD25+ and CD38+) CD4+ and CD8+ T lymphocytes in peripheral blood were analysed for DNA content in 15 HIV+ patients and 10 healthy age- and sex-matched control subjects. As expected, all HIV+ patients had elevated percentage levels of activated CD4+ HLA-DR+, CD4+ CD25+, CD8+ HLA-DR+, CD8+ CD25+ and CD8+ CD38+ T lymphocytes compared with control subjects (P < 0.001 for all). Percentage levels of CD4+ HLA-DR+ and CD8+ HLA-DR+T lymphocytes in the 'proliferative' (S-G2M) phase of the cell cycle were also higher in the HIV+ patients compared with controls (P < 0.001 for both). The percentage levels of proliferative CD4+ CD25+, CD8+ CD25+ and CD8+ CD38+ lymphocytes were, however, similar in HIV+ patients and controls, indicating that the proliferative fraction of cells in vivo was confined to the HLA-DR+ subset and absent from the CD25+ and CD38+ populations. Four HIV+ patients had grossly elevated levels of CD8+ lymphocytes which were CD38+ (> 95%) and confined to the pre-G0-G1 phase of the cell cycle, suggesting these may be cells committed to apoptosis. These observations indicate an increase in the proliferative capacity of HLA-DR+ T lymphocytes in HIV infection in vivo. The reduced DNA content in other populations (e.g. CD38+ CD8+ lymphocytes) of some patients with advanced HIV disease suggests that these cells are apoptotic. Thus our results define both proliferative and apoptotic processes as a spectrum of activation-related events in HIV infection.

ADP-ribosyl Cyclase↗
PubMed1995

Ovarian tumour antigens as potential targets for immune gene therapy.

Major new developments in the understanding of the molecular mechanisms involved in immune recognition of self, and immune mediated rejection of foreign antigens, have resulted in the development of a variety of novel therapeutic strategies for the treatment of cancer. Cornerstones of the advances in this area have been the identification of tumour antigens and demonstration of immune recognition of neoplastic cells, most notably in malignant melanoma. There are now a number of clinical immune gene therapy trials in progress for the treatment of cancer by stimulating immune mediated rejection of malignant cells. Here we examine the evidence for immune recognition of ovarian tumour cells and the presence of putative ovarian tumour antigens as potential targets for immune gene therapy of ovarian carcinoma.

Antigen-Presenting Cells↗
PubMed1994

Importance of persistent cellular and humoral immune changes before diabetes develops: prospective study of identical twins.

OBJECTIVES: To determine the pattern of cellular and humoral immune changes associated with insulin dependent diabetes before diabetes develops. DESIGN: Prospective study over 10 years of 25 non-diabetic identical twins of patients with insulin dependent diabetes. The non-diabetic twins were followed up either till they developed diabetes or to the end of the study. SETTING: Teaching hospital. SUBJECTS: 25 non-diabetic identical cotwins of patients with diabetes; 46 controls of the same sex and similar age tested over the same period. Of the 25 twins (total follow up 144 patient years), 10 developed diabetes (prediabetic twins); the remainder were followed up for a mean of 7.7 years. MAIN OUTCOME MEASURES: Results of glucose tolerance tests or fasting blood glucose concentrations at each sample point. Measurements of activated T lymphocytes, expressing the HLA-DR antigen, islet cell antibodies, and insulin autoantibodies in samples. RESULTS: All 10 prediabetic twins had both cellular and humoral changes initially and in most samples before diabetes was diagnosed (activated T lymphocytes in 39/40, islet cell antibodies in 45/47, and insulin autoantibodies to islet cells and insulin were detected infrequently (in 8/54, 6/69, and 0/69 samples, respectively). The combination of cellular and humoral (islet cell antibodies or insulin autoantibodies) immune changes were detected in all 10 of the prediabetic twins but in only one of the 15 non-diabetic twins (P < 0.001). The positive predictive value in this cohort of increased percentages of activated T cells and the presence of antibodies to islet cells or insulin on two consecutive occasions was 100%. CONCLUSION: Most of the twins had cellular or humoral immune changes at some stage. A combination of cellular and humoral immune changes and their tendency to persist is highly predictive of insulin dependent diabetes and distinguishes twins who develop diabetes from those who do not.

Adolescent↗
PubMed1994

Lymphocyte subset abnormalities, autoantibodies and their relationship with HLA DR types in children with type 1 (insulin-dependent) diabetes and their first degree relatives.

Type 1 (insulin-dependent) diabetes mellitus is associated with abnormalities of circulating lymphocyte subsets and autoantibodies. To investigate the prevalence of these in non-diabetic siblings and non-diabetic patients of children with Type 1 diabetes, we analysed T-cell subsets of function and activation in 31 families with an index case of Type 1 diabetes and related these to autoantibodies and HLA DR type. Using two and three colour cytofluorimetry, we studied total and activated (HLA-DR+) CD3+, CD4+, CD8+, lymphocytes and on CD4+ lymphocytes the CD45RA/RO "naive" and "memory" cell phenotypes. Diabetic children (mean duration of disease 3.1 years) had a reduced total lymphocyte count (p < 0.05), their non-diabetic siblings a reduced CD4+ T-helper cell count (p < 0.05), and their parents a reduced percentage and number of CD3+ T cells (p < 0.01 and p < 0.05) compared with age-matched control subjects. Diabetic children, their siblings and parents all had significantly increased levels of activated CD4+ T-helper cells (p < 0.01, p < 0.05 and p < 0.01). In diabetic children and their siblings there was a significant over-expression of the CD45RO "memory" cell marker and significant under-expression of the CD45RA "naive" cell marker, whilst these were normal in the parents. Islet cell antibody positive diabetic children had significantly higher levels of CD45RO-expressing CD4+ lymphocytes than those who were islet cell antibody negative (p < 0.05). Amongst the siblings and parents, possession of HLA-DR4 was associated with lower percentages of CD4+ and higher percentages of CD8+ T cells. These findings extend current knowledge about the role of immunoregulatory CD45RA/RO cells in Type 1 diabetes. In addition, they demonstrate lymphocyte subset abnormalities in unaffected family members, some of which may be influenced by HLA DR alleles.

Adult↗
PubMed1994

Primary and secondary liver/kidney microsomal autoantibody response following infection with hepatitis C virus.

Liver/kidney microsomal autoantibody type 1 (LKM-1), which characterizes a subtype of autoimmune hepatitis, is also found in some patients with chronic hepatitis C virus (HCV) infection. Whether HCV and LKM-1 are accidentally or causally related is unknown. This case report describes a child who became infected by HCV after liver transplantation for end-stage liver disease caused by alpha 1-antitrypsin deficiency. LKM-1 was detected by immunofluorescence, anti-microsomal reactivity by Western blotting, anti-HCV and anti-GOR by immunoenzymatic assays, and HCV RNA by polymerase chain reaction. Two weeks after HCV infection, immunoglobulin (Ig) M LKM-1 appeared, followed by IgG1 LKM-1, with titers increasing to 1/2560; antibodies to a 50-kilodalton liver microsomal protein appeared 2 months later. Sera from day 1 posttransplant became positive for HCV RNA. HCV RNA was also detected in a liver biopsy specimen obtained 3 months after surgery. The patient did not produce anti-HCV and anti-GOR antibodies throughout the study and had no histological evidence of hepatitis. The temporal relationship between HCV infection and LKM-1 production suggests that HCV may trigger a primary autoimmune response. The lack of liver damage attributable to autoimmunity or viral infection may be caused by immunosuppression.

Antibody Formation↗