Unusual interferon gamma measurements with QuantiFERON-TB Gold and QuantiFERON-TB Gold In-Tube tests

Introduction

Interferon gamma (IFN-γ) release assays, such as QuantiFERON®-TB Gold test (QFT-G) and QuantiFERON®-TB Gold In-Tube test (QFT-GIT) are designed to detect M. tuberculosis (Mtb) infection. Recognition of unusual IFN-γ measurements may help indicate inaccurate results.

Methods

We examined QFT-G and QFT-GIT results from subjects who had two or more tests completed. We classified unusual IFN-γ measurements as: 1) High Nil Concentration (HNC) when IFN-γ concentration in plasma from unstimulated blood exceeded 0.7 IU/mL; 2) Low Mitogen Response (LMR) when Mitogen Response was <0.5 IU/mL; 3) Very Low Mitogen Response (VLMR) when Mitogen Response was ≤−0.5 IU/mL; and 4) Very Low Antigen Response (VLAR) when the response to a Mtb antigen was ≤−0.35 IU/mL and ≤−0.5 times the IFN-γ concentration in plasma from unstimulated blood.

Results

Among 5,309 results from 1,728 subjects, HNC occurred in 234 (4.4%) tests for 162 subjects, LMR in 108 (2.0%) tests for 85 subjects, VLMR in 22 (0.4%) tests for 21 subjects, and VLAR in 41 (0.8%) tests for 39 subjects. QFT-GIT had fewer HNC, VLMR, and VLAR (p = 0.042, 0.004, and 0.067 respectively); QFT-G had fewer LMR (p = 0.005). Twenty-four (51.6%) of 47 subjects with positive results and HNC were negative or indeterminate by all other tests. Thirteen (61.9%) of 21 subjects with positive results and LMR were negative or indeterminate by all other tests.

Conclusion

Unusual IFN-γ measurements including HNC, LMR, VLMR, and VLAR were encountered in small numbers, and in most instances were not seen on simultaneously or subsequently performed tests. To avoid erroneous diagnosis of Mtb infection, IGRAs with unusual IFN-γ measurements should be repeated with another blood sample and interpreted with caution if they recur.     

Divergent effects of mycobacterial cell wall glycolipids on maturation and function of human monocyte-derived dendritic cells

Background

Mycobacterium tuberculosis (Mtb) is able to evade the immune defenses and may persist for years, decades and even lifelong in the infected host. Mtb cell wall components may contribute to such persistence by modulating several pivotal types of immune cells. Dendritic cells (DCs) are the most potent antigen-presenting cells and hence play a crucial role in the initial immune response to infections by connecting the innate with the adaptive immune system.

Principal Findings

We investigated the effects of two of the major mycobacterial cell wall-associated types of glycolipids, mannose-capped lipoarabinomannan (ManLAM) and phosphatidylinositol mannosides (PIMs) purified from the Mtb strains H37Rv and Mycobacterium bovis, on the maturation and cytokine profiles of immature human monocyte-derived DCs. ManLAM from Mtb H37Rv stimulated the release of pro-inflammatory cytokines TNF, IL-12, and IL-6 and expression of co-stimulatory (CD80, CD86) and antigen-presenting molecules (MHC class II). ManLAM from M. bovis also induced TNF, IL-12 and IL-6 but at significantly lower levels. Importantly, while ManLAM was found to augment LPS-induced DC maturation and pro-inflammatory cytokine production, addition of PIMs from both Mtb H37Rv and M. bovis strongly reduced this stimulatory effect.

Conclusions

These results indicate that the mycobacterial cell wall contains macromolecules of glycolipid nature which are able to induce strong and divergent effects on human DCs; i.e while ManLAM is immune-stimulatory, PIMs act as powerful inhibitors of DC cytokine responses. Thus PIMs may be important Mtb-associated virulence factors contributing to the pathogenesis of tuberculosis disease. These findings may also aid in the understanding of some earlier conflicting reports on the immunomodulatory effects exerted by different ManLAM preparations.     

The Clinically-tested S1P Receptor Agonists,FTY720 and BAF312, Demonstrate Subtype-Specific Bradycardia (S1P1) and Hypertension (S1P3) in Rat

Sphingosine-1-phospate (S1P) and S1P receptor agonists elicit mechanism-based effects on cardiovascular function in vivo. Indeed, FTY720 (non-selective S1P_X receptor agonist) produces modest hypertension in patients (2–3 mmHg in 1-yr trial) as well as acute bradycardia independent of changes in blood pressure. However, the precise receptor subtypes responsible is controversial, likely dependent upon the cardiovascular response in question (e.g. bradycardia, hypertension), and perhaps even species-dependent since functional differences in rodent, rabbit, and human have been suggested. Thus, we characterized the S1P receptor subtype specificity for each compound in vitro and, in vivo, the cardiovascular effects of FTY720 and the more selective S1P_1,5 agonist, BAF312, were tested during acute i.v. infusion in anesthetized rats and after oral administration for 10 days in telemetry-instrumented conscious rats. Acute i.v. infusion of FTY720 (0.1, 0.3, 1.0 mg/kg/20 min) or BAF312 (0.5, 1.5, 5.0 mg/kg/20 min) elicited acute bradycardia in anesthetized rats demonstrating an S1P₁ mediated mechanism-of-action. However, while FTY720 (0.5, 1.5, 5.0 mg/kg/d) elicited dose-dependent hypertension after multiple days of oral administration in rat at clinically relevant plasma concentrations (24-hr mean blood pressure = 8.4, 12.8, 16.2 mmHg above baseline vs. 3 mmHg in vehicle controls), BAF312 (0.3, 3.0, 30.0 mg/kg/d) had no significant effect on blood pressure at any dose tested suggesting that hypertension produced by FTY720 is mediated S1P₃ receptors. In summary, in vitro selectivity results in combination with studies performed in anesthetized and conscious rats administered two clinically tested S1P agonists, FTY720 or BAF312, suggest that S1P₁ receptors mediate bradycardia while hypertension is mediated by S1P₃ receptor activation.     

The electrical response of Phaseolus vulgaris roots to abrupt exposure to hydroquinone

Previous reports have suggested the primary mode of action of the allelochemical hydroquinone involves disruption of root cell membrane transport. Here we report the effects of hydroquinone on common bean (Phaseolus vulgaris) plants. Growth of leaves, roots and stems were all inhibited by 14 day exposure to 0.01 mM or 0.25 mM hydroquinone. Chlorophyll fluorescence (Fv/Fm) was inhibited by 0.25 mM hydroquinone. The membrane potential of P. vulgaris root cortex cells briefly hyperpolarized and subsequently slowly transiently depolarized upon abrupt exposure to a range of hydroquinone concentrations. Both the hyperpolarization and depolarization were concentration dependent but appeared saturable. Root cells exposed to 0.03 mM hydroquinone hyperpolarized 3.4 mV (+/− 0.6 s.e.) 3 minutes after the start of exposure then depolarized 36.7 mV (+/− 3.9) with no effect evident after 24 hours. Individual recordings showed a response to as little as 0.001 mM hydroquinone. Exposure of P. vulgaris root cells to arbutin, a nontoxic monoglucoside of hydroquinone, produced a similar but much smaller (approximately 25%) electrical response. Exposure of root cells of Antennaria microphylla, a known allelopathic source (donor plant) of hydroquinone, also produced a much smaller hyperpolarization and depolarization response. It is concluded that the electrical response to hydroquinone by P. vulgaris root cells and the changes in membrane transport they represent are not sufficiently large or long lasting enough to disrupt mineral and water uptake leading to plant injury. The possibility, however, that these events are related to initiation of signal transduction events leading to cell death is discussed.Key words: allelopathy, hydroquinone, membrane potential, depolarization, hyperpolarization, Phaseolus vulgaris, Antennaria microphylla     

Concentration profile of mRNA of kinine B1 and B2 receptors in the evaluation of colon pathologies

Colon pathologies involve the activation of a number of inflammation mediators: cytokines, prostanoids and kinines. The expression patterns of the genes associated with their activation may provide a very sensitive marker of the physiological condition of the cells. This paper demonstrates certain statistically significant differences (p = 0.008) between the expression patterns of kinine B1 and B2 receptor encoding genes for colitis ulcerosa and a control group. The ratio of kinine B1/B2 concentrations changes significantly, on the average from 1.3 for a tissue assessed as healthy to 6.6 for colitis ulcerosa.     

Expression of the histone H3 gene in the evaluation of cellular proliferation in colitis ulcerosa

A comparison of the number of mRNA molecules of histone H3 in 1 microg total RNA extracted from colon sections sampled during colonoscopy was used to evaluate cellular proliferation activity in the rectum and sigmoid, in normal tissue and in colitis ulcerosa. Samples with similar intensity of the disease were selected for the study. Statistically significant differences between both groups of rectal sections were found in the expression of histone H3 encoding genes. The statistically significant result (p = 0.0485) indicates a more active division of cells in the healthy rectum, with no statistically significant differences in the sigmoid (p=0.9575).     

Synergistic activation of protein kinase Calpha, -betaI, and -gamma isoforms induced by diacylglycerol and phorbol ester: roles of membrane association and activating conformational changes

Protein kinase Calpha (PKCalpha) has been shown to contain two discrete activator sites with differing binding affinities for phorbol esters and diacylglycerols. The interaction of diacylglycerol with a low-affinity phorbol ester binding site leads to enhanced high-affinity phorbol ester binding and to a potentiated level of activity [Slater, S. J., Ho, C., Kelly, M. B., Larkin, J. D. , Taddeo, F. J., Yeager, M. D., and Stubbs, C. D. (1996) J. Biol. Chem. 271, 4627-4631]. In this study, the mechanism of this enhancement of activity was examined with respect to the Ca2+ dependences of membrane association and accompanying conformational changes that lead to activation. The association of PKCalpha with membranes containing 12-O-tetradecanoylphorbol 13-acetate (TPA) or 1, 2-dioleoylglycerol (DAG), determined from tryptophan to dansyl-PE resonance energy transfer (RET) measurements, was found to occur at relatively low Ca2+ levels (相似文献   

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