Technetium-labelled leucocytes using diethyldithiocarbamate: preliminary report on in vitro studies.

Diethyldithiocarbamate (DDC) forms a lipid soluble complex with 99Tcm-pertechnetate which is rapidly incorporated into leucocytes in vitro. In seven healthy volunteers, a 'crude' leucocyte suspension was obtained by sedimnetaion and centrifugation and incubated with 99Tcm-DDC complex. Labelling efficiency was found to be 73 +/- 14% (SD). The mean activity remaining on the cells after hourly incubations with plasma was 77 +/- 5%. Percoll-saline differential cell analysis showed that 69 +/- 3% of the activity was associated with the granulocytes, 12 +/- 4% with the lymphocytes/monocytes, 11 +/- 4% with the platelets and 8 +/- 1% with contaminating erythrocytes (n = 3). The mean labelling efficiency decreased by 14% when the leucocyte count was reduced from 42 X 10(6) to 21 X 10(6) cells. Over the range 21 X 10(6) to 5.2 X 10(6) cells there was no decrease in labelling efficiency.