BIMODAL GRANULOCYTE TRANSIT-TIME THROUGH THE HUMAN LUNG DEMONSTRATED BY DECONVOLUTION ANALYSIS

The lungs are an important site of granulocyte pooling. The aim of the study is to quantify pulmonary vascular granulocyte transit time usin g deconvolution analysis: as has previously been performed to measure pulmonary red cell transit time. Granulocyte and red cell studies were performed in separate groups of patients. Both cell types were labell ed with Tc-99m, which for granulocyte labelling was complexed with hex amethylpropyleneamine oxime (HMPAO). The red cell impulse response fun ction (IRF) was monoexponential with a median transit time of 4.3 s. T he granulocyte IRF was biexponential in 19 of 22 subjects, 18 of whom had systemic inflammation (inflammatory bowel disease, systemic vascul itis or graft-vs-host disease) and four were controls without inflamma tory disease. The median transit time of the fast component ranged fro m 20 to 25 s and of the slow component 120-138 s in the four patient g roups. The fraction of cells undergoing slow transit correlated signif icantly with (a) mean granulocyte transit time and (b) the fraction sh owing shape change in vitro. We conclude that granulocyte transit time through the pulmonary circulation is bimodal and that shape-changed ( activated) cells transit more slowly that non-activated cells. The siz e of the fraction undergoing slow transit is closely related to mean g ranulocyte transit time and is an important determinant of the size of the pulmonary vascular granulocyte pool.