Effects of temperature on radiochemical purity and immunoreactivity of radiolabeled monoclonal antibody 1H10.

OBJECTIVE: This study was undertaken to investigate the effects of temperature on preserving the radiochemical purity and immunoreactivity of 125I- and 131I-labeled monoclonal antibody (MAb) 1H10--an antibody against human cervical carcinoma cell-surface antigen. METHODS: An antibody-irrelevant human melanoma cell line, H2269, served as the control group. Iodine-125 and 131I radiolabeling of MAbs 1H10 and H2669 was performed by the chloramine-T method. All the prepared MAbs were divided into aliquots and stored at 4, -20, and -70 degrees C for 2-14 d. The radiochemical purity and immunoreactivity of the labeled antibodies in set conditions were measured by thin-layer chromatography and a modified index, respectively, after a single freeze-and-thaw cycle. RESULTS: Reduced release of free radioiodide and better preservation of immunoreactivity were observed in the radiolabeled MAbs stored at -70 degrees C than in those stored at -20 degrees C or 4 degrees C. The extent of free iodide dissociation and immunologic binding degradation of 125I-labeled MAb 1H10 appeared milder than that of 131I-labeled MAb under the same conditions. However, both 125I- and 131I-labeled MAb stored at -70 degrees C or -20 degrees C retained more than 90% radiochemical purity for at least 3d. CONCLUSION: Freezing provides an appropriate alternative for reducing radiolysis and preserving immunoreactivity of radioiodinated MAbs. MAb 1H10, labeled with either 125I or 131I and stored at temperatures of -20 degrees C or below for 3 d after labeling, appeared stable in both radiolabeling and binding studies in vitro and was still acceptable for in vivo use.

Perfusion scan in pulmonary tumor microembolism: report of a case.

A 76-year-old male patient was admitted to our hospital with the chief complaint of dyspnea. A chest CT scan showed pericardial effusion, mediastinal lymphadenopathy and a tumor in the right ventricle with invasion to the main trunk of the pulmonary artery. A 99mTc MAA perfusion lung scan revealed multiple small subsegmental peripheral defects and a "fissure sign", while the 133Xe ventilation scan was normal. After the chest CT scan and scans of both lungs, tumor microembolism was highly suspected. Open chest surgery was performed. A huge tumor in the right ventricle involving the main trunk of the pulmonary artery was found. In addition, multiple tumor thrombi in the pulmonary arteries and veins were also noted. The pathology was metastatic squamous cell carcinoma. Thereafter, the primary lesion was found by bronchoscopy. The final diagnosis was squamous cell carcinoma of the right lower lobe bronchus with metastases to the right ventricle and pulmonary vessels, and in association with pulmonary tumor microembolism. We present this uncommon case and describe the pulmonary perfusion pattern of the tumor microembolism.