In vitro 51Cr and 32P-DFP labeling of granulocytes in man.

Several labels have been used for in vitro label ing of granulocytes. 32P-diisopropylfluorophosphate (32P-DFP) was originally used by Athens, et al in 1959 (1 ) . These authors found a disappearance half-time from circulating blood of 6.6 hr (4—10hr) for 32P-DFP-labeled granulocytes. In 1966 Dresch and Najean (2—4) labeled normal granulocytes with 51Cr, using the technique published by McCall (5) for leukemic cells, and found a disappearance half time of 19 ± 4 hr for normal granulocytes. In a previous paper (2) we proposed three hy potheses to explain the discrepancy between the re suits obtained with 51Crand 32P-DFP-iabeled gran ulocytes: I . Cells are uniformly labeled, regardlessof age, by 51Cr whereas 32P-DFP labels older cells more readily. This hypothesis could explain a shorter disappearance half-time with 32P-DFP labeling if granulocytes do not leave the cir culation in a strictly random way. 2. The longer disappearance half-time in the cir culation of 51Cr-labeled granulocytés is due to metabolic damage which hampers their migra tion into the tissues but does not alter their intravascular survival time. 3. 32P-DFP is eluted in vivo although there is no evidence for in vitro elution (1 ), or 32P-DFP alters the labeled cells and causes a shorter life span. In both cases, the disappearance half time of 32P-labeled cells would be less than normal. None of these hypotheses could be substantiated when we proposed them. However, in this paper we wish to present data on sequential and simultaneous in vitro labeling of granulocytes by 51Cr and 32P-DFP which explain the different results obtained with the two methods. We have found a very good correlation between the disappearance half-time of granulocytes labeled separately by these two radionuclides. Such a corre lation enabled us to use a double-labeling method to demonstrate a qualitative granulocyte anomaly in some cases of chronic leukopenia. Indeed, when one uses only one radionuclide, two separate labelings are needed, first of the patient's own granulocytes and, second, of homologous normal granulocytes (3,6). However, several consecutive tests are often difficult to complete, and their interpretation is always sub ject to controversy since in the interval between the tests a change in leukocyte kinetics may occur. Dou ble labeling by 51Cr of autologous granulocytes and by 32P-DFP of homologous granulocytes would allow us to compare the life span of normal and pathologi cal granulocytes under the same conditions if a con sistent correlation exists between the disappearance half-time of cells labeled by these two tracers.