111Indium-labelled leukocytes for measurement of inflammatory activity in arthritis.

Mononuclear leukocytes and granulocytes have been separated and labelled with 111In-oxine (111In). We show that granulocytes as well as monocytes can be labelled with 111In without serious adverse effects on the viability of the cells. The separated and 111In-labelled cells from patients with rheumatoid arthritis and psoriatic arthritis were reinfused into the patients and detection was made with a gamma camera over the inflamed joints. The study shows that images and semi-quantitative indices of leukocyte accumulation in the joints could be obtained in these patients. We suggest that the method may be a sensitive indicator of non exsudative synovitis and allow assessment of inflammation in joints not amenable to physical examination. This method also opens new possibilities to measure the migration of different leukocytes over the synovial membrane.