Currently, no reliable data are available on the volume or on the cellular content of pleural fluid in normal humans. In analogy with bronchoalveolar lavage (a technique enabling retrieval of small volumes of epithelial lining fluid from the lung), we developed a pleural lavage (PL) technique consisting of injection and retrieval of 150 ml of saline into the right pleural space, performed during a thoracoscopic sympathicolysis procedure in otherwise healthy subjects suffering from essential hyperhidrosis. With urea used as an endogenous marker of dilution, measured mean right-sided pleural fluid volume was 8.4 +/- 4.3 ml. In a subgroup of subjects, we confirmed that right- and left-sided pleural fluid volumes were similar. Expressed per kilogram of body mass, total pleural fluid volume in normal, nonsmoking humans is 0.26 +/- 0.1 ml/kg. Total cell count in the PL fluid of nonsmoking normal subjects yielded a median of 91 x 10(3) white blood cells (WBC) per milliliter of lavage fluid (interquartile range [IR] = 124 x 10(3) cells/ml). Taking into account a measured dilution factor of 18.86, the total WBC count in the original pleural fluid was 1,716 x 10(3) cells/ml. Differential cell counts yielded a predominance of macrophages (median: 75%; IR: 16%) and lymphocytes (median: 23%; IR: 18%). Mesothelial cells (median: 1%; IR: 2%), neutrophils (median: 0%; IR: 1%), and eosinophils (median: 0%; IR: 0%) were only marginally present. There were no significant differences between males and females or between right- and left-sided pleural fluid in total and differential cell counts. In contrast, in smokers a small but statistically significant increase in pleural fluid neutrophils (median: 1%; IR: 2%; p < 0.015) was observed. In conclusion, PL performed during thoracoscopy for sympathicolysis allowed for the first time determination of the volume and of the total and differential cell contents of the pleural fluid present in normal human pleura.

Leukaemic cells show a low clonogenic activity and a heterogeneous proliferative response to growth factors. We investigated whether this could be due to an altered expression of growth factor receptors on the leukaemic precursors. Receptors for G-CSF, stem cell factor (SCF), IL-3, IL-6 and IL-7 were detected on CD34+ cells in AML and B-lineage ALL with monoclonal antibodies and flow cytometry. The expression was compared with that on myeloid and B-lymphoid CD34+ cells in normal bone marrow. Leukaemic CD34+ cells expressed the same receptors as their normal counterparts. AML and B-lineage ALL could be distinguished by the growth factor receptor profile of their CD34+ cells. SCFR, G-CSFR and IL-6Ralpha were found in AML, IL-7R in B-lineage ALL and IL-3Ralpha in both. IL-3Ralpha was upregulated in AML and B-lineage ALL CD34+ cells, while samples with low or high expression were present for the other receptors. This variable expression could correlate with the heterogeneous response of leukaemic cells to growth factors. Functional studies on isolated CD34+ cells are needed to investigate this further.

The expression of adhesion molecules on CD34+ cells in acute myeloid leukemia (AML) and B‐lineage acute lymphoblastic leukemia (B‐lineage ALL) was compared with that on the myeloid and B‐lymphoid CD34+ cells in normal bone marrow. Bone marrow aspirates of 10 patients with AML, 8 patients with B‐lineage ALL and of 6 healthy volunteers were examined. The phenotype of the CD34+ cells was determined with a double immunofluorescence method and flow cytometry. CD34+ cells in AML and B‐lineage ALL showed a lower expression of VLA‐2 and VLA‐3 and a higher expression of ICAM‐1 and LFA‐3 than their normal bone marrow counterparts. AML CD34+ cells had less L‐selectin but more VLA‐5 on their surface membrane than normal myeloid CD34+ cells. B‐lineage ALL CD34+ cells showed an overexpression of LFA‐3. In individual patients deficiencies or over‐expression of the β1 integrin chain, VLA‐4, PECAM‐1 or HCAM also occurred. An abnormal adhesive capacity of the leukemic cells may influence their proliferation, their localisation and apoptosis. An aberrant expression of adhesion molecules may be used for the detection of minimal residual leukemia in these patients.

Growth factors regulate the proliferation and differentiation of hemopoietic cells. Their effect on hemopoietic precursors differs according to the ontogenic source of the cells. Cord blood and mobilized blood CD34(+) cells have a higher sensitivity for growth factors than bone marrow CD34(+) cells. This could be due to a higher expression of growth factor receptors. Therefore, we examined the expression of receptors for stem cell factor (SCF), interleukin-6 (IL-6), IL-3, granulocyte colony-stimulating factor (G-CSF) and IL-7 on the CD34(+) cells of cord blood, mobilized peripheral blood and bone marrow. The receptors were detected with monoclonal antibodies and flow cytometry. The majority of the CD34(+) cells in bone marrow clearly expressed SCFR; they showed a moderate positivity for IL-3Ralpha and a weak staining for G-CSFR and IL-6 Ralpha. Less than 10% of the cells were IL-7R positive. Cord blood CD34(+) cells showed a higher expression of SCFR and a lower positivity for G-CSFR and IL-6Ralpha. Mobilized blood CD34(+) cells showed a lower expression of SCFR and G-CSFR, and a higher positivity for IL-3Ralpha. This was not solely due to the presence of more myeloid precursors in mobilized blood, as the growth factor receptor profile did not correspond to that of early or late myeloid CD34(+) precursors in normal bone marrow. Changes induced by the mobilization procedure occurred as well. In conclusion, the higher sensitivity for growth factors of hemopoietic precursors in cord blood and mobilized blood cannot be explained by a general increase of the growth factor receptor expression on the CD34(+) cells.