Quantification of the distribution of the marginating granulocyte pool in man

The kinetics of autologous granulocytes, separated from whole blood and labelled with 111In-tropolonate with continuous maintenance in plasma, have been studied in man, using a gamma camera and computer, with the aim of quantifying the distribution of the marginating granulocyte pool (MGP). We have used 3 approaches: dynamic gamma camera imaging immediately following i.v. injection of labelled cells, comparison of the activity signal from 111In-granulocytes with that from previously injected 111In-labelled red cells and absolute quantification of 111In present in liver, spleen and blood. Deconvolution analysis of the hepatic and peripheral blood time activity curves indicated that hepatic granulocyte transit time was 2.5 +/- SE 0.14 min. By comparison with 111In red cells, hepatic transit time was calculated to be 7.4 +/- SE 0.82 that of red cells, which, assuming an hepatic red cell content of 6% that of the total red cell mass, is equivalent to a transit time of 1.8 min. By comparison with 111In red cells, lung granulocyte transit time as a factor of red cel transit time was 5.4 +/- SE 0.7 at 5 min and 2.5 +/- SE 0.13 at 40 min after granulocyte injection. Using these kinetic data, in combination with previously published values for splenic granulocyte transit time, it was calculated that, 5 min after injection, the MGP accounted for 54% of the total blood granulocyte pool (TBGP), was 90% filled, and was distributed between spleen (19%), liver (26%), lung (33%) and the remainder of the body (22%). At 40 min, the MGP accounted for 60% of the TBGP, had equilibrated with the circulating granulocyte pool (CGP), and was distributed between the spleen, liver, lung and remainder of the body according to the following respective percentages: 35, 25, 10 and 30. The total granulocyte contents of the spleen and liver calculated on the basis of the kinetic data were 21% and 22% respectively and in broad agreement with the values, 34 and 23% respectively, calculated from quantitative scanning. It was concluded that about 70% of the body's MGP was present in the spleen, liver and lung. If the MGP is itself 60% of the TBGP then only about 18% of the TBGP marginates in extra-hepatosplenopulmonary sites.