Technetium-99m-MAG3 versus iodine-123-OIH: renal clearance and distribution volume as measured by a constant infusion technique.

The renal clearance and distribution volume of 99Tc-mercaptoacetyltriglycine (MAG3) and 123I-o-iodohippurate (OIH) were determined separately in six normal male volunteers using the constant infusion clearance technique in order to validate single injection clearance techniques and subsequently the normal values for these parameters. MAG3 renal clearance was 257 +/- 24 ml/min/1.73 m2, compared to the OIH clearance of 556 +/- 46 ml/min/1.73 m2 resulting in a MAG3/OIH clearance ratio of 0.47 +/- 0.06. The MAG3 and OIH apparent distribution volumes at steady-state were 14.8 +/- 3.7 and 19.4 +/- 5.3 liters, respectively, the latter value approximating the extra cellular fluid volume. Urinary excretion in the 0-30-min period after intravenous administration was 64.4 and 70.2% for MAG3 and OIH, respectively. This investigation revealed some significant differences in the normal values of the renal clearance and distribution volume of MAG3 compared with other studies.     

Alloreactivity against repeated HLA mismatches of sequential islet grafts transplanted in non-uremic type 1 diabetes patients

BACKGROUND: Islet transplantation can restore insulin production in type 1 diabetes patients. However, survival of the islet allografts will face rejection or recurrence of autoimmunity or a combination of both. In a study on islet-after-kidney transplants, we previously reported that islet cell recipients presented low T-cell alloresponses for HLA mismatches that were shared by the islet cell graft and the prior kidney graft, that is, repeated mismatch, while vigorous responses were measured against novel HLA mismatches. METHODS: We now investigated T-cell alloreactivity to repeated HLA-mismatches in three non-uremic type 1 diabetic patients each receiving three sequential islet cell implants. RESULTS: These islet-after-islet recipients patients exhibited low or absent responses to repeated mismatches to the first graft which was accompanied by sustained graft function, and reduced responsiveness towards subsequent grafts. In one patient, T-cell responses towards these mismatches were noticed following new mismatches in subsequent grafts, with loss of graft function. CONCLUSION: These case reports further support the view that subsequent islet implantations can reduce alloreactivity for repeated HLA mismatches. They demonstrate the usefulness of monitoring T-cell reactivity against islet allografts to correlate immune function with graft survival and to identify conditions for preservation of beta-cell function.     

Longitudinal Immune Responses and Gene Expression Profiles in Type 1 Leprosy Reactions

Purpose

Leprosy, a chronic disease initiated by Mycobacterium leprae, is often complicated by acute inflammatory reactions. Although such episodes occur in at least 50 % of all leprosy patients and may cause irreversible nerve damage, no laboratory tests are available for early diagnosis or prediction of reactions. Since immune- and genetic host factors are critical in leprosy reactions, we hypothesize that identification of host-derived biomarkers correlated to leprosy reactions can provide the basis for new tests to facilitate timely diagnosis and treatment thereby helping to prevent tissue damage.

Methods

The longitudinal host response of a leprosy patient, who was affected by a type 1 reaction (T1R) after MDT-treatment, was studied in unprecedented detail, measuring cellular and humoral immunity and gene expression profiles to identify biomarkers specific for T1R.

Results

Cytokine analysis in response to M. leprae revealed increased production of IFN-γ, IP-10, CXCL9, IL-17A and VEGF at diagnosis of T1R compared to before T1R, whereas a simultaneous decrease in IL-10 and G-CSF was observed at T1R. Cytokines shifts coincided with a reduction in known regulatory CD39⁺CCL4⁺ and CD25^high T-cell subsets. Moreover, RNA expression profiles revealed that IFN-induced genes, (V)EGF, and genes associated with cytotoxic T-cell responses (GNLY, GZMA/B, PRF1) were upregulated during T1R, whereas expression of T-cell regulation-associated genes were decreased.

Conclusions

These data show that increased inflammation, vasculoneogenesis and cytotoxicity, perturbed T-cell regulation as well as IFN-induced genes play an important role in T1R and provide potential T1R-specific host biomarkers.     

A user-friendly, highly sensitive assay to detect the IFN-gamma secretion by T cells

OBJECTIVES: Development of a user-friendly test alternative to ELISA-based assays to detect IFN-gamma by in vitro cultured peripheral blood mononuclear cells (PBMC) stimulated with pathogen-derived antigens. DESIGN AND METHODS: The molecular components of an operational IFN-gamma ELISA-based test were applied in a lateral flow (LF) immuno-sandwich assay using up-converting phosphor (UCP) reporter particles. The analytical sensitivity of the UCP-LF IFN-gamma assay (ULIGA) was determined and the assay was qualitatively validated with a selection of 60 supernatants derived from PBMC cultures stimulated with M. leprae derived antigens, mitogen or medium alone. RESULTS: ULIGA indicated an analytical sensitivity better than 2 pg/mL, and demonstrated four orders of magnitude dynamic range. The assay correlated well with the IFN-gamma ELISA. CONCLUSIONS: ULIGA allows detection well below the cutoff value (100 pg/mL) used to define positive responses in the IFN-gamma ELISA. The test procedure is less demanding in respect to equipment and labor, and is suited for testing single samples.     

Holmium-166 poly lactic acid microspheres applicable for intra-arterial radionuclide therapy of hepatic malignancies: effects of preparation and neutron activation techniques

Since one of the most frequent sites of human metastatic cancer is the liver, particularly in colon and rectum carcinoma, there is a special need for the development of an effective therapy. This study describes the parameters for reproducible production of poly lactic acid (PLA) microspheres with an average diameter of 37 μm and labelled with neutron-activated holmium-166 (E _max=1.84 MeV, t _1/2=26.8 h), suitable for use in internal radionuclide therapy of liver metastases. It is demonstrated that holmium-loaded PLA microspheres can be prepared by a relatively simple method, with incorporation of 17.0%±0.6% holmium (n=5), and that 20 GBq can be obtained from 400 mg neutron activatable microspheres. In order to produce this high amount of activity, the microspheres must be free of water and irradiation must be performed in a polyethylene vial, with a relatively low neutron flux (5×10¹³ cm^–2 s^–1) within 1 h. Under these well-defined conditions minor surface changes were seen which barely affected total volume and consequently total radioactivity of the microspheres with a diameter of 20–50 μm. Overall structural integrity was maintained in terms of form and size. In vitro analyses showed that >99.3% of ¹⁶⁶Ho activity was retained in the microspheres after 192 h incubation in PBS, plasma and leucocytes, while in liver homogenate retention was still 98.4%. Received 23 January and in revised form 8 March 1999     

MRI-based biodistribution assessment of holmium-166 poly(L-lactic acid) microspheres after radioembolisation

Objectives

To demonstrate the feasibility of MRI-based assessment of the intrahepatic Ho-PLLA-MS biodistribution after radioembolisation in order to estimate the absorbed radiation dose.

Methods

Fifteen patients were treated with holmium-166 (¹⁶⁶Ho) poly(L-lactic acid)-loaded microspheres (Ho-PLLA-MS, mean 484 mg; range 408–593 mg) in a phase I study. Multi-echo gradient-echo MR images were acquired from which R ₂ ^* maps were constructed. The amount of Ho-PLLA-MS in the liver was determined by using the relaxivity r ₂ ^* of the Ho-PLLA-MS and compared with the administered amount. Quantitative single photon emission computed tomography (SPECT) was used for comparison with MRI regarding the whole liver absorbed radiation dose.

Results

R ₂ ^* maps visualised the deposition of Ho-PLLA-MS with great detail. The mean total amount of Ho-PLLA-MS detected in the liver based on MRI was 431 mg (range 236–666 mg) or 89?±?19 % of the delivered amount (correlation coefficient r?=?0.7; P?<?0.01). A good correlation was found between the whole liver mean absorbed radiation dose as assessed by MRI and SPECT (correlation coefficient r?=?0.927; P?<?0.001).

Conclusion

MRI-based dosimetry for holmium-166 radioembolisation is feasible. Biodistribution is visualised with great detail and quantitative measurements are possible.

Key Points

? Radioembolisation is increasingly used for treating unresectable primary or metastatic liver tumours. ? MRI-based intrahepatic microsphere biodistribution assessment is feasible after holmium-166 radioembolisation. ? MRI enables quantification of holmium-166 microspheres in liver in a short imaging time. ? MRI can estimate the whole liver absorbed radiation dose following holmium-166 radioembolisation.     

Neutron activation of holmium poly(L-lactic acid) microspheres for hepatic arterial radioembolization: a validation study

Poly(L-lactic acid) microspheres loaded with holmium-166 acetylacetonate (¹⁶⁶Ho-PLLA-MS) are a novel microdevice for intra-arterial radioembolization in patients with unresectable liver malignancies. The neutron activation in a nuclear reactor, in particular the gamma heating, damages the ¹⁶⁶Ho-PLLA-MS. The degree of damage is dependent on the irradiation characteristics and irradiation time in a particular reactor facility. The aim of this study was to standardize and objectively validate the activation procedure in a particular reactor. The methods included light- and scanning electron microscopy (SEM), particle size analysis, differential scanning calorimetry, viscometry, thermal neutron flux measurements and energy deposition calculations. Seven hours-neutron irradiation results in sufficient specific activity of the ¹⁶⁶Ho-PLLA-MS while structural integrity is preserved. Neutron flux measurements and energy deposition calculations are required in the screening of other nuclear reactors. For the evaluation of microsphere quality, light microscopy, SEM and particle size analysis are appropriate techniques.     

Radioactive Holmium Acetylacetonate Microspheres for Interstitial Microbrachytherapy: An <Emphasis Type="Italic">In Vitro</Emphasis> and <Emphasis Type="Italic">In Vivo</Emphasis> Stability Study

Purpose  

The clinical application of holmium acetylacetonate microspheres (HoAcAcMS) for the intratumoral radionuclide treatment of solid malignancies requires a thorough understanding of their stability. Therefore, an in vitro and an in vivo stability study with HoAcAcMS was conducted.     

In vitro binding characteristics for cesium of two qualities of prussian blue, activated charcoal and Resonium-A.

The in vitro binding characteristics of radioactive 137Cs to two forms of Prussian blue [colloidally (soluble) K3Fe[Fe(CN)6] and insoluble Fe4[Fe(CN)6]3] and to activated charcoal and sodium polystyrene sulfonate (Resonium-A) were investigated by constructing Langmuir isotherms at pH = 1.0, 6.5 and 7.5 at 37 degrees C. At the three pHs investigated, 137Cs binding to activated charcoal and sodium polystyrene sulfonate was negligible. Binding of 137Cs to insoluble Prussian blue exceeded that for the soluble form and was pH dependent for both formulations. Maximum binding capacities were 87 mg/g (pH = 1.0), 194 mg/g (pH = 6.5) and 238 mg/g (pH = 7.5) for the insoluble form and 48 (pH = 1.0), 73 (pH = 6.5) and 78 (pH = 7.5) for the soluble form. As activated charcoal did not bind 137Cs, charcoal hemoperfusion is of no value. This has been confirmed by an in vitro experiment, using a Gambro Adsorbs 300 C cartridge.