U937 cell line: impact of CSFs, IL-6 and IFN-gamma on the differentiation and the Leu-CAM proteins expression.

Differentiation of the U937 cell line can be induced by various agents. We have investigated the differentiation abilities of gamma-interferon (IFN-gamma), interleukin-6 (IL-6), macrophage and granulocyte-macrophage colony-stimulating factors (M-CSF + GM-CSF) or the combinations IL-6 + M-CSF + GM-CSF and IFN-gamma + M-CSF + GM-CSF on the U937 cells by studying the morphology, cytochemical activity and several functional properties. The expression of the Leu-CAM proteins (CD11a, CD11b, CD11c, CD18) was also evaluated during the culture period. Our results show that the cytokines used in this study inhibit to a certain extent the proliferation of the tumor cells and drive the cells toward a differentiation phenotype that has several characteristics in common with mononuclear phagocytes, such as the expression of CD14, phagocytosis and release of superoxide anions. The adhesion molecules CD11b alpha chain and CD18 beta chain were strongly induced on the U937 cells with a maximal expression of the CD11b on the cells cultured with either M-CSF + GM-CSF or the combinations of IL-6 and IFN-gamma with M-CSF + GM-CSF. Conversely, for CD11a and CD11c alpha chains a rather low enhancement of the expression was noticed. In our culture system, cells incubated with the combination of M-CSF + GM-CSF exhibited differentiation characteristics which appeared to be largely potentialized when cytokines such as IL-6 or IFN-gamma were added.

Adhesion and Transendothelial Migration of Human Monocytes: Role of Cytokine (IL3, GM-CSF) Activated Endothelial Cells.

In this study we have investigated the effect of GM-CSF and IL3 on Human Umbilical Vein Endothelial Cells (HUVEC). We studied the adhesion properties of HUVEC for non stimulated human elutriated monocytes, as well as the transendothelial migration of these cells. We analysed the expression of adhesion molecules (VLA4/CDw49d, VCAM1/CD106, LFA1/CD11a, ICAM1/CD54, CD18, L-selectin/CD62L, PeCAMl/CD31, ELAM1/CD62E) induced in monocyte adhesion and transmigration. Optimal conditions of HUVEC stimulation with IL3 and GM-CSF were obtained with 100 U/ml of each cytokine. IL3 and GM-CSF were found to induce HUVEC proliferation, more than twofold at day 7 of the culture compared to controls. HUVEC proliferation was not stimulated by IL1α, a slight inhibitory effect was observed at 250 and 500 U/ml. We showed that GM-CSF, IL3 and their combination mimic on activation like status that on which is expressed by an enhancement of adhesion and migration of non stimulated monocytes to and across cytokines activated HUVEC monolayers. After 6 hours activation with IL3 or GM-CSF, more than 60% of the monocytes are adherent to HUVEC after a contact of 30 minutes (vs 30.8 ± 4.6% for untreated control HUVEC). This percentage increased to 80% after a 7 days culture period in presence of the same cytokines (vs 40 ± 5.1% for untreated control HUVEC). IL3 was very effective at inducing monocyte transendothelial migration. The potency of IL3 is seen to be 2 to 3 fold higher than GM-CSF in this system. GM-CSF and IL3 modulate on HUVEC the expression of adhesion molecules induced in monocyte adhesion and transendothelial migration processes. We showed that anti-ELAMl inhibit in part monocyte migration (8.5 ± 3% vs 46.33 ± 4.03% without MoAb; vs 5.1 ± 2% with ICAM1, ELAM1 and VCAMI MoAbs).