Labelling lymphocytes with technetium99m-hexamethyl propyleneamine oxime for scintigraphy: an improved labelling procedure

99mTc-HMPAO labelling inhibits cell motility and cell proliferation and induces apoptosis of NC-NC cells

(99m)Tc-hexamethyl-propylenamine-oxime ((99m)Tc-HMPAO)-labelled leukocytes have been used in standard diagnostic procedures for the detection of infection and inflammation. Although some investigators have already pointed out that labelling of leukocytes with (99m)Tc-HMPAO has detrimental effects on the cells, still very little is known regarding the effects of ionizing radiation on lymphocyte function. The effects of (99m)Tc-HMPAO-labelling on lymphocyte adhesion, proliferation, mitotic index, migration and apoptosis were evaluated. The lymphoblastoid cell line NC-NC was used as the lymphocyte population. (99m)Tc-HMPAO-labelling decreased cell adhesion, proliferation, mitotic index and motility, whereas it induced apoptosis and cell-cycle arrest. The rate of decrease in cell proliferation was up to 70% (P<0.001) by day 4 after labelling. (99m)Tc-HMPAO-labelling led a 35% decrease (P<0.001) in adhesion ability of the cells on fibronectin at 16h. Using the Boyden chamber motility assay, it was shown that both spontaneous and monocyte chemotactic protein (MCP-1)-induced lymphocyte motility were strongly reduced by (99m)Tc-HMPAO-labelling. The decrease in motility was approximately five-fold (P<0.05). In addition, a 12-fold increase (P<0.05) was observed in apoptosis of the (99m)Tc-HMPAO-treated cells compared with control cells. Besides, it was shown that cell-cycle arrest was induced starting from the 3rd day after treatment with (99m)Tc-HMPAO. Our observations indicate that (99m)Tc-HMPAO-labelling has damaging effects on lymphocyte function including cell adhesion, proliferation, mitotic index, motility and cell cycle under in vitro conditions.

Synthesis of 99mTc-HYNIC-interleukin-12, a new specific radiopharmaceutical for imaging T lymphocytes

PURPOSE

Few radiopharmaceuticals have been described for the study of lymphocyte trafficking despite its high clinical relevance. The main difficulty resides in the identification of a suitable highly specific probe to target these cells. Interleukin-12 (IL12) is a heterodimeric cytokine which plays a key role in the development of Th(1) lymphocytes. The aims of the present study were to label IL12 with (99m)Tc, to evaluate its ability to bind to activated T lymphocytes in vitro and to study its biodistribution in normal mice and mice affected by autoimmune colitis.

METHODS

IL12 was derivatised with HYNIC-NHS and labelled with( 99m)Tc. An in vitro binding assay was performed on KIT225 cells, an IL12 receptor-positive cell line. (99m)Tc-IL12 biodistribution in normal mice was studied. Targeting experiments were performed in Balb/c mice injected with KIT225 cells and in mice with chemically induced chronic colitis.

RESULTS

(99m)Tc-IL12 labelling efficiency ranged between 75% and 85%. Saturation binding analysis revealed a K (d) of 2.09 nM. Results of biodistribution studies showed a predominant hepatic route of excretion. A significant degree of uptake in the spleen and thymus was also observed. In mice injected with KIT225 cells, (99m)Tc-IL12-specific uptake in these cells increased over time. (99m)Tc-IL12 also accumulated significantly in bowel of mice affected by TNBS-induced colitis showing T lymphocyte infiltration at histology, while accumulation in colon from control animals was negligible.

CONCLUSION

We conclude that this radiolabelled cytokine is a suitable candidate for specific in vivo imaging of T lymphocytes: a step forward in molecular imaging of immune-mediated processes.

Imaging of intestinal lymphocyte homing by means of pinhole SPECT in a TNBS colitis mouse model

BACKGROUND AND AIMS

The increasing knowledge of the molecular basis of leukocyte trafficking results in the development of novel anti-inflammatory strategies for inflammatory bowel disease (IBD). For optimal evaluation of therapy efficacy, information about inflammatory activity in bowel segments or lymphocyte recirculation and kinetics in the follow-up of experimental treatment for IBD is needed. The aim of this study was to evaluate a non-invasive scintigraphic technique, able to assess lymphocyte trafficking in a trinitrobenzene sulfonic acid (TNBS) induced mouse colitis model of IBD.

METHODS

TNBS sensitized and non-sensitized murine total splenocytes were labeled in vitro with 111In-oxine and injected into either control or TNBS colitis BALB/c mice. Biodistribution and specific radioactive uptake, representing transferred cells, were determined by serial dedicated animal planar scintigraphy and pinhole SPECT of the abdomen 4, 24 and 48h post injection of labeled cells. In addition, the severity of inflammation was determined by histological scoring.

RESULTS

Migration of 111In labeled splenocytes to the colon increased in time and was maximal at 48h after administration. The highest specific radioactive uptake ratio in the colon after 48h was observed in mice with TNBS colitis that received TNBS sensitized lymphocytes. Histological scoring confirmed the presence of colitis in the TNBS treated groups.

CONCLUSION

Homing of TNBS-sensitized lymphocytes can be assessed in vivo by means of dedicated animal pinhole SPECT. Generally, this technique enables serial measurement of specific cell trafficking with potential of in vivo evaluation of novel anti-inflammatory strategies in inflammatory bowel disease.

Active inflammatory bowel disease: evaluation with 99mTc (V) DMSA scintigraphy

PURPOSE

To evaluate the use of pentavalent (V) technetium 99m (99mTc) dimercaptosuccinic acid (DMSA) scintigraphy for the assessment of disease activity in patients with inflammatory bowel disease (IBD).

MATERIALS AND METHODS

99mTc (V) DMSA scintigraphy was performed in 76 patients. There were 36 patients with active IBD (11 with ulcerative colitis, 25 with Crohn disease), 28 patients with inactive disease (eight with ulcerative colitis, 20 with Crohn disease), and 12 patients with miscellaneous bowel disease. Sensitivity and specificity of 99mTc (V) DMSA scintigraphy in the diagnosis of IBD were calculated. In the group with active IBD, the disease activity and laboratory indices, as well as the endoscopic and histologic activity, were compared with the scanning activity index. Correlation coefficients between them were calculated with the Spearman rank test.

RESULTS

99mTc (V) DMSA scintigraphy had a 92% (33 of 36) sensitivity and an 86% (24 of 28) specificity in the detection of active IBD. A significant correlation between disease activity indices and scintigraphy score was demonstrated. Endoscopic and histologic activity was significantly correlated (P =.005 and.02, respectively, overall disease activity) with the scanning activity score. Of the group of patients with miscellaneous bowel disease, three with ischemic colitis had negative findings at scintigraphy.

CONCLUSION

99mTc (V) DMSA scintigraphy provides a noninvasive, practical, and accurate assessment of IBD activity.

Technetium-99m scintigraphy to visualize T-cell homing in vivo: a preclinical study

The knowledge of lymphocyte distribution is very usefulness in monitoring therapeutic treatments. We present here a method employed in clinical practice, the scintigraphy, to study in the rat the physiologic lymphocyte traffic. Rat T cells labeled with 99mTc were injected in syngeneic animals, and their fate was studied by serial scintigraphic scanning. Sorted naïve CD4+ CD45RC(bright) T cells homed to lymphoid organs and accumulated in spleen. CD4+ CD45RC(dim) memory lymphocytes first reached the liver and the lungs and recirculated. The results obtained by using the scintigraphic method to in vivo study the lymphocyte homing in rats are comparable to those obtained with previously used experimental methods. We consider the scintigraphic method a useful tool to in vivo track lymphocytes and to address therapeutic treatment in men.

Biological imaging for the diagnosis of inflammatory conditions

Radiopharmaceuticals used for in vivo imaging of inflammatory conditions can be conveniently classified into six categories according to the different phases in which the inflammatory process develops. The trigger of an inflammatory process is a pathogenic insult (phase I) that causes activation of endothelial cells (phase II); there is then an increase of vascular permeability followed by tissue oedema (phase III). Phase IV is characterised by infiltration of polymorphonuclear cells, and a self-limiting regulatory process called apoptosis is observed (phase V). If the inflammatory process persists, late chronic inflammation takes place (phase VI). In some pathological conditions, such as organ-specific autoimmune diseases, chronic inflammation is present early in the disease. The aim of nuclear medicine in the field of inflammation/infection is to develop noninvasive tools for the in vivo detection of specific cells and tissues. This would allow early diagnosis of initial pathophysiological changes that are undetectable by clinical examination or by other diagnostic tools, and could also be used to evaluate the state of activity of the disease during therapy. These potential applications are of great interest in clinical practice. In this review, we describe the various approaches that have been developed in the last 25 years of experience. Recent advances in the diagnosis of inflammatory processes have led to the development of specific radiopharmaceuticals that are intended to allow specific stage-related diagnosis.