Gernot P. Tilz

Soluble receptors for tumour necrosis factor in clinical laboratory diagnosis

Abstract:  Soluble tumour necrosis factor receptors (sTNF‐Rs) play a role as modulators of the biological function of tumour necrosis factor‐α (TNF‐α) in an agonist/antagonist pattern. In various pathologic states the production and release of sTNF‐Rs may mediate host response and determine the course and outcome of disease by interacting with TNF‐α and competing with cell surface receptors. The determination of sTNF‐Rs in body fluids such as plasma or serum is a new tool to gain information about immune processes and provides valuable insight into a variety of pathological conditions. Regarding its immediate clinical use, sTNF‐Rs levels show high accuracy in the follow‐up and prognosis of various diseases. In HIV infection and sepsis, sTNF‐Rs concentrations strongly correlate with the clinical stage and the progression of disease and can be of predictive value. Determination of sTNF‐Rs also gives useful information for monitoring cancer and autoimmune diseases. The information provided is often even superior to that obtained with classical disease markers, probably due to the direct involvement of the “TNF system” in the pathogenetic mechanisms in these patients. The available data imply that the measurement of sTNF‐Rs, especially of the sTNF‐R 75kD type, is a useful adjunct for quantification of the Th1‐type immune response, similar to other immune activation markers such as neopterin and β2‐microglobulin. Endogenous sTNF‐Rs concentrations appear to reflect the activation state of the TNF‐α/TNF receptor system.

Tryptophan degradation and immune activation in Alzheimer's disease.

Summary. Alzheimers disease (AD) is likely associated with systemic immune activation. During immune response, interferon-gamma stimu-lates indoleamine 2,3-dioxygenase (IDO) converting tryptophan to N-formylkynurenine followed by kynurenine in an ensuing step. Thus, IDO activity is estimated by the kynurenine per tryptophan quotient (Kyn/Trp). In 21 patients suffering from AD, in 20 controls of similar age, and in 49 blood donors we measured serum tryptophan and kynurenine concentrations by HPLC. Lower tryptophan concentrations were found in elderly control subjects compared to blood donors (62.1 vs. 73.0 μM, p < 0.005). Tryptophan concentrations tended to be still lower in AD patients (54.4 μM, p = 0.07) compared to elderly controls. Enhanced tryptophan degradation in patients was reflected by significantly increased Kyn/Trp (46.1 vs. 34.1 in elderly controls, p < 0.05). Correlations were found in patients between Kyn/Trp and concentrations of soluble immune markers in serum, i.e., neopterin, interleukin-2 receptor and tumor necrosis factor receptor (all p < 0.001). Increased Kyn/Trp was associated with reduced cognitive performance. Tryptophan degradation due to immune activation may exert impact on the pathogenesis of AD.

Increased concentrations of neopterin in carotid atherosclerosis

Activation of T-cells and macrophages may play a role in the pathogenesis of atherosclerosis. Therefore, serum concentrations of the immune activation markers neopterin and soluble interleukin-2 receptor were compared with routine laboratory parameters, candidate risk variables and degree of carotid atherosclerosis. Study subjects were 561 individuals (293 men and 268 women) aged between 50 and 79 years who were enrolled in a cross-sectional community based study (Ischemic Heart Disease and Stroke Prevention Study, Bruneck, Italy). Extent of carotid atherosclerosis was quantitated by an ultrasound B-mode procedure based scoring system. Detailed physical examination and quantification of laboratory and candidate risk variables were performed. By univariate as well as multivariate statistical analyses, serum concentrations of neopterin but not soluble interleukin-2 receptor were significantly higher in subjects with carotid atherosclerosis (men, 8.5 +/- 2.7 nmol/l neopterin; women, 9.6 +/- 3.3) than in those without (men, 6.7 +/- 2.3, P < 0.0001; women, 7.5 +/- 2.3, P < 0.0001). The data show that the macrophage-derived immune activation marker neopterin is closely correlated with the extent of carotid atherosclerosis. Chronic activation of immune cells, preferentially of macrophages, may play a key role in atherogenesis and/or progression of atherosclerosis.

Association between immune activation, changes of iron metabolism and anaemia in patients with HIV infection

Abstract:  The pathogenesis of anaemia associated with human immunodeficiency virus infection is still far from being understood. It cannot be explained by direct effects of the virus on the haematopoietic system. Recent data suggest a role for immune activation. In a cross‐sectional study we compared blood cell counts, haemoglobin and erythropoietin levels of 63 HIV‐seropositive individuals with immune activation markers (interferon‐γ, serum and urine neopterin, and β2‐microglobulin) and with parameters or iron metabolism (serum iron, transferrin, free iron binding capacity, ferritin). We found significant correlations between the concentrations of haemoglobin and the immune activation markers and erythropoietin concentrations. Additional significant correlations existed between the parameters of iron metabolism and haemoglobin levels, and ferritin correlated inversely with transferrin. In sum, low haemoglobin levels in patients were associated with enhanced cellular immune activation, as seen by increased interferon‐γ, neopterin and β2‐microglobulin, and with changes of iron metabolism: low haemoglobin was associated with low transferrin and free iron binding capacity and high ferritin levels. Endogenous release of cytokines such as interferon‐γ‐inhibiting crythropoiesis may be one underlying cause of anaemia in these patients.

Serum soluble markers of immune activation and disease activity in systemic lupus erythematosus

We investigated a possible association between markers of immune activation and disease activity in 52 patients with systemic lupus erythematosus (SLE). Serum concentrations of neopterin, beta- 2-microglobulin, 55 kD-type soluble tumor necrosis factor receptor, soluble interleukin-2 receptor and soluble CD8 were compared to the Index of European Consensus Lupus Activity Measurement (ECLAM). All markers of immune activation, except sCD8, significantly correlated with ECLAM. Stepwise multiple linear regression analysis revealed erythrocyte sedimentation rate and neopterin to correlate best with ECLAM (multiple correlation coefficient = 0.74, P < 0.001). The study shows that serum neopterin concentrations are a useful independent index for disease activity in SLE. The finding of enhanced concentrations of various parameters of immune activation in patients confirm a role of the T cell and macrophage activation in the pathogenesis of SLE.

Activated immune system in patients with Huntington's disease

Abstract Abnormalities of immune system compartments were determined in 12 patients with Huntingtons disease (eight males, four females; age 42.4 ± 11.7 years) and 11 controls (7 males, 4 females; age 47.0 ± 12.0). All patients were free from infectious diseases. Serum concentrations of a panel of serum soluble markers of immune activation were investigated, namely neopterin, 55-kDa-type soluble tumor necrosis factor receptor (sTNF-R), interleukin-2-receptor (sIL-2R), kynurenine, tryptophan, immunoglobulins (Ig) A, M and G as well as routine laboratory tests. Compared to controls, we found significantly higher serum levels of IgA (p < 0.01), sTNF-R, sIL-2R, neopterin, and complement component C3 (all p < 0.05), and serum tryptophan was decreased (p < 0.001). Higher concentrations of circulating immune complexes, cardiolipin antibodies, IgM, neopterin and lower tryptophan were associated with loss of cognitive function as assessed by the minimental-test. Five patients died within 1 year after measurements were performed. In these patients IgM, circulating immune complexes and neopterin concentrations were higher compared to survivors and serum tryptophan was lower. The data indicate an activation of various immune system compartments in Huntingtons disease and that systemic immunological alterations might be important in the course of the disease.

Detection and Quantification of Small Numbers of Circulating Tumour Cells in Peripheral Blood Using Laser Scanning Cytometer (LSC

Abstract The detection of circulating tumour cells disseminated from solid tumours requires extremely sensitive methods. Molecular genetic methods, which are most sensitive, are not applicable to solid tumours because no tumour-specific genetic markers are available. Detection of disseminated tumour cells by immunocytochemistry is time-consuming, whereas fluorimetry is fast and quantitative. The laser scanning cytometer (LSC®) provides an automated microscopic procedure for screening up to 5×104 cells in suitable time. Using this system together with an enrichment procedure which allows up to ten thousand-fold enrichment, we have quantified minimal numbers of tumour cells. In a model system, breast cancer cell line cells diluted into peripheral blood mimicked seeding of tumour cells into the periphery. After staining with fluorochrome-conjugated anti-epithelial antibody, slides were screened for positive events directly or after enrichment with antibody-coated magnetic beads. One positive cell was unequivocally detectable in 104 cells and 50 out of 60 tumour cells were reliably recovered from a 20 ml blood volume, equal to 1–2 cells per 107, after magnetic bead enrichment. This method allows quantitation of tumour cells in peripheral blood and bone marrow in reasonable time and will, for the first time, enable extensive investigation of the seeding behaviour of tumours.

Influence of Lamotrigine and Topiramate on MDR1 Expression in Difficult‐to‐Treat Temporal Lobe Epilepsy

Summary:  Purpose: Overexpression of the multiple drug resistance gene 1 (MDR1) was quantified in brain tissue from Coriaria lactone (CL)‐kindled Sprague–Dawley (SD) rats after treatment with lamotrigine (LTG) or topiramate (TPM) and compared with that found in rats treated with carbamazepine (CBZ) and valproate (VPA).

Degradation of Tryptophan in Neurodegenerative Disorders

In patients with neurodegenerative disorders, namely Alzheimers disease and Huntingtons disease, we compared serum concentrations of tryptophan, kynurenine and the kynurenine per tryptophan ratio with concentrations of soluble immune activation markers. Significantly lower tryptophan concentrations were observed in the patients, and lower tryptophan levels as well as higher kynurenine levels and higher kynurenine per tryptophan ratios correlated with higher concentrations of neopterin, and soluble receptors for TNF and interleukin-2. In both groups of patients tryptophan concentrations correlated inversely with the degree of mental retardation. No such association existed for the duration of the disease. The data show that systemic chronic immune activation in patients with Alzheimers disease and Huntingtons disease is associated with significant degradation of tryptophan, which is most likely due to activation of indoleamine (2,3)-dioxygenase by immunologic stimuli. Further studies will be necessary to investigate a potential role of tryptophan degradation in the pathogenesis of neurodegenerative disorders.

Increased immune activation during and after physical Eexercise

The present study has been performed to examine the pattern of immune response during and following a long-duration of physical exercise. We have measured plasma concentrations of serum soluble immune activation markers namely soluble interleukin-2 receptor (sIL-2R), soluble CD8 (sCD8), soluble intercellular adhesion molecule 1 (sICAM-1), soluble CD23 (sCD23), soluble tumor necrosis factor receptor (sTNF-R) and neopterin in 18 individuals before, during (ascent: 3 h, descent: 2 h) and after an alpine tour. Compared to baseline levels, all the parameters were significantly increased on top of the mountain and/or after descent. Within 36 hours after the tour sIL-2R, sCD8 and sICAM-1 decreased. In contrast, sTNF-R and neopterin levels remained higher than baseline throughout the study, only partially decreasing 24 and 36 hours from start. These data show immune system activation induced by physical exercise. The increase of parameters sTNF-R and neopterin, reflecting activation of macrophages, was sustained. The data suggest that immune activation phenomena may be involved in the pathogenesis of impaired immune function after exercise and the exercise-induced asthma.