An established immune response against ovalbumin is suppressed by a transferable serum factor produced after ovalbumin feeding: a role of CD25+ regulatory cells

We have previously demonstrated that rats fed ovalbumin (OVA) develop a tolerogenic activity in serum, which upon transfer induces tolerance to OVA and suppression of the immune response to a bystander antigen. Here, we have extended these studies and analysed if the tolerogenic activity in serum could suppress an established immune response in the recipients. Rats were immunized with OVA, 4 and 1 week prior to the transfer of serum from either OVA-fed or control animals. Rats that received serum from OVA-fed donors had significantly lower delayed-type hypersensitivity (DTH) reaction against OVA 1 week after the serum transfer compared with the controls, and the levels of immunoglobulin (IgG) anti-OVA antibodies were significantly lower 2 and 4 weeks after serum transfer. Monomeric OVA in amounts corresponding to the OVA transferred with serum did not induce the reduction of DTH response or IgG anti-OVA antibody levels. In vitro, the proliferation of OVA-stimulated spleen cells, taken from recipients of tolerogenic serum, was significantly lower compared with spleen cells from the controls. The in vitro suppression seemed to be mediated by a population of CD25+ cells, because the removal of such cells from OVA-stimulated spleen cell suspensions resulted in increased proliferation in cultures from rats receiving tolerogenic serum. Our results showed that the tolerogenic serum factor can suppress an established immune response in recipient animals, possibly through induction of regulatory CD25+ cells. Whether this capacity might be used to influence chronic inflammatory conditions needs to be investigated.     

Prediction of AVM obliteration after stereotactic radiotherapy using radiobiological modelling

This study was carried out in order to derive the radiobiological parameters of the dose-response relation for the obliteration of arteriovenous malformation (AVM) following single fraction stereotactic radiotherapy. Furthermore, the accuracy by which the linear Poisson model predicts the probability of obliteration and how the haemorrhage history, location and volume of the AVM influence its radiosensitivity are investigated. The study patient material consists of 85 patients who received radiation for AVM therapy. Radiation-induced AVM obliterations were assessed on the basis of post-irradiation angiographies and other radiological findings. For each patient the dose delivered to the clinical target volume and the clinical treatment outcome were available. These data were used in a maximum likelihood analysis to calculate the best estimates of the parameters of the linear Poisson model. The uncertainties of these parameters were also calculated and their individual influence on the dose-response curve was studied. AVM radiosensitivity was assumed to be the same for all the patients. The radiobiological model used was proved suitable for predicting the treatment outcome pattern of the studied patient material. The radiobiological parameters of the model were calculated for different AVM locations, bleeding histories and AVM sizes. The range of parameter variability had considerable effect on the dose-response curve of AVM. The correlation between the dosimetric data and their corresponding clinical effect could be accurately modelled using the linear Poisson model. The derived response parameters can be introduced into the clinical routine with the calculated accuracy assuming the same methodology in target definition and delineation. The known volume dependence of AVM radiosensitivity was confirmed. Moreover, a trend relating AVM location with its radiosensitivity was observed.     

A nonlinear model of the arterial vessels within a limb segment

The relationship between the arterial blood pressure and the volume of the arteries within a segment of an extremity is nonlinear. The present paper shows how the flow and volume pulsations of the arteries within a limb segment can be simulated taking this property into account. An electrical model was constructed comprising one resistor and two voltage dependent ‘capacitors’, the latter corresponding to the pressure dependent elasticity, or compliance, of the arteries. Adequate simulations were obtained over a wide pressure range, which is impossible with linear models. The nonlinear, i.e. pressure dependent, relationship between the volume and pressure of arteries, observed under static conditions, must also be taken into consideration when studying pulsatile events with models whether mathematical or physical.     

GABAB receptors in various in vitro and in vivo models of epilepsy: a study with the GABAB receptor blocker CGP 35348.

The effect of the GABAB receptor blocker CGP 35348 on epileptic processes in vitro and in vivo was studied. In hippocampal slices of the rat maintained in vitro, CGP 35348 (100 microM) induced a moderate increase in the frequency of extracellularly recorded spontaneous epileptiform burst discharges induced in CA3 by penicillin (1.2 mM), bicuculline (5 microM) and low Mg(2+) (0.1 mM). This effect was observed in 50-75% of the slices. A similar but less consistent increase was also observed in CA1 in bicuculline and low Mg2+. Data obtained by intracellular recordings from CA1 pyramidal cells in the presence of bicuculline (10 microM) demonstrated that CGP 35348 (100 microM) increased the duration of the paroxysmal depolarization underlying an evoked epileptiform burst and reduced the early component of the after hyperpolarization which followed the burst. In mice pretreated with isoniazid, CGP 35348 (300 mg/kg, i.p.) significantly increased the number of convulsing mice. However, convulsions induced by submaximal doses of pentylenetetrazol, picrotoxin or strychnine were not facilitated by CGP 35348. We conclude that GABAB receptors appear to exert a suppressant effect on various kinds of epileptiform discharges of hippocampal neurons in vitro. In vivo, however, the role of GABAB receptors in regulating convulsions is less prominent since only isoniazid-induced convulsions were facilitated by GABAB receptor blockade.     

Comparison of flagellum and sonicate antigens for serological diagnosis of Lyme borreliosis

A sonicate antigen and two concentrations of a purified flagellum antigen ofBorrelia burgdorferi were compared for serological diagnosis of Lyme borreliosis by an enzyme immunoassay (EIA). Generally, the higher concentration of flagellum antigen was found to be superior to the lower concentration, which was diluted eight times compared to the higher concentration. The diagnostic sensitivity for IgG antibody detection increased from 13 % in the sonicate EIA to 31 % in the best flagellum EIA assay (p=0.01) in sera from patients with erythema migrans (n=70), and from 34 % to 55 % (p=0.01) in sera from patients with neuroborreliosis (n=77). However, the sensitivity for IgG in sera from patients with acrodermatitis chronica atrophicans (n=20) was high in both assays: 90 % in the sonicate EIA compared to 95 % in the flagellum EIA. Regarding IgM, there was no significant difference between the sensitivity of the assays in sera from any of the patient groups. The sensitivity values for IgM and IgG in cerebrospinal fluid (CSF) from patients with neuroborreliosis were also without significant differences. Sera and CSF from patients with meningitis/encephalitis of non-Borrelia etiology (n=35), multiple sclerosis (n=9) or syphilis (n=24), served as controls. The flagellum EIA showed a significantly improved specificity for IgG in CSF from controls with syphilis (p<0.01). It is concluded that purifiedBorrelia burgdorferi flagellum antigen is superior to a sonicate antigen, especially for serodiagnosis of the early stages of Lyme borreliosis.     

Episodic variations of prolactin, thyroid-stimulating hormone, luteinizing hormone, melatonin and cortisol in infertile women with subclinical hypothyroidism

Preliminary data have suggested that female infertility due to corpus luteum insufficiency may be caused by subclinical hypothyroidism [exaggerated thyroid-stimulating hormone (TSH) response to thyrotrophin- releasing hormone (TRH) stimulation]. L-Thyroxine supplementation has been recommended to achieve pregnancies in subclinical hypothyroid women. This controlled study was carried out in order to investigate the biochemical diagnosis of subclinical hypothyroidism as a possible infertility factor. Five infertile patients (aged 25-36 years) with subclinical hypothyroidism (n = 4, stimulated TSH >20 microU/ml) or primary hypothyroidism (n = 1) and five healthy controls (aged 22-39 years) with normal thyroid function (stimulated TSH <15 microU/ml), regular cycles and no history of infertility were studied in the early follicular phase. In the pre-study evaluation, eight of 23 volunteers (34.8%) had to be excluded because of subclinical hypothyroidism with stimulated TSH values (TSHs) >15 microU/ml. Cycle function of patients and controls was compared by the method of LH pulse pattern analysis. Therefore blood samples were drawn every 10 min during a 24 h period. Sleep was recorded from midnight to 7 a.m. Repetition of the TRH tests at the end of the 24 h blood sampling period confirmed the difference in stimulated TSH values of the two study groups. Pulse analysis for luteinizing hormone (LH), TSH and prolactin showed no differences between patients and controls for pulse frequency, amplitude, height, length, area under curve (AUC) and the 24 h mean. Even the hypothyroid patient had a normal LH pulse pattern. Additional measurement of melatonin in pooled sera every 30 min gave the well-documented diurnal profiles during day and night for both groups. Patients had significantly higher melatonin values at seven time points during the night. Peaks for LH, TSH, prolactin and cortisol were correlated with the sleep stages wake, rapid eye movement, 1 + 2 and 3 + 4. We concluded that corpus luteum insufficiency in female infertility cannot be explained by subclinical hypothyroidism and thus should not be treated with L-thyroxine for fertility reasons.      

Nicotinamide reduces high secretion of IFN-gamma in high-risk relatives even though it does not prevent type 1 diabetes.

Type 1 diabetes (T1D) is an autoimmune disease suggested to be of a T helper (Th)1-like origin. This study aimed to investigate the Th1-like and Th2-like profile in high-risk individuals during the prediabetic phase and the immunologic effect of treatment with nicotinamide. High-risk first-degree relatives of T1D patients participating in the European Nicotinamide Diabetes Intervention Trial (ENDIT) were treated with either nicotinamide or placebo. Peripheral blood mononuclear cells (PBMC) were obtained during the prediabetic phase and close to the onset of manifest T1D and from nondiabetic high-risk individuals. Using the sensitive enzyme-linked immunospot (ELISPOT) technique to distinguish Th1-like from Th2-like lymphocytes, secretion of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) was analyzed from PBMCs spontaneously and after in vitro stimulation with the diabetes-associated autoantigens, glutamic acid decarboxylase 65 (GAD65, protein and peptide, aa 247-279), recombinant tyrosine phosphatase (IA-2), and heat shock protein (HSP, aa 437-460). High-risk individuals showed high spontaneous as well as autoantigen-induced IFN-gamma secretion. Secretion of IFN-gamma and the IFN-gamma/IL-4 ratio, induced by autoantigens, decreased in individuals developing T1D (p < 0.05), whereas nondiabetic individuals showed an increased IL-4 response (p < 0.05). Thus, a Th1-dominated cytokine profile observed in high-risk individuals inclined toward a diagnosis of diabetes. Nicotinamide caused decreased spontaneous (p = 0.05) and in vitro autoantigen-induced IFN-gamma secretion (p < 0.05) and may play a role in immune regulation, even though it has not been shown to prevent T1D.