In vivo labelling of granulocytes using 123I-tagged anti-granulocyte antibodies.

On the basis of previous work with various monoclonal antibodies (Mab) raised against carcino-embryonic antigen (CEA), the anti-CEA Mab 47 was identified which selectively reacted with a surface glycoprotein (95 kDa; NCA 95) of normal human granulocytes. This new tracer was quality tested and radioiodinated with 123I (123I Mab 47) for clinical use according to established procedures. Extended in vitro studies revealed a high selectivity for granulocytes without inhibiting their vital functions. In vivo cell binding to the granulocyte pool was completed very rapidly and remained unchanged over 24 h. For clinical use one dose consisting of 120 mcg of Mab was labelled with 4-5 mCi of 123I. Clinical interest was mainly concentrated on cases of osteomyelitis, infected allografts and abdominal and brain abscesses. After injection of 123I Mab 47, infectious lesions were usually seen after 3-5 h or could be excluded after 24 h. Because of high counting rates the image quality was excellent and single photon emission computerized tomography (SPECT) could be performed for an exact topographical localization of the lesions. No adverse reactions have been seen. It is concluded that there are distinct advantages of the new method compared with scanning of 111In-labelled leucocytes. However, despite this and the low dose of antibodies administered, we recommend restriction of immunoscintigraphy of infectious lesions before a clinically relevant immunization can be excluded.