EFFECT OF THROMBOPOIETIN (TPO) AND GRANULOCYTE COLONY STIMULATING FACTOR (G-GSF) ON PLATELETS AND POLYMORPHONUCLEAR LEUKOCYTES (PMN).

SCHATTNER, MIRTA; POZNER, ROBERTO G.; GOROSTIZAGA, ALEJANDRA; LAZZARI, MARIA A.

Washington DC, USA.

Congreso; XVIIIth International Society on Thrombosis and Haemostasis Congress; 1999

International Society on Thrombosis and Haemostasis

Tpo  and G-csf could be administered together in aplastic patients. We evaluated the effect of Tpo and G-csf alone or in combination on platelet and PMN functional responses. Tpo and G-csf up to 500 ng/ml induced neither aggregation nor platelet ATP release. Tpo (100 ng/ml) but not G-csf synergized with submaximal ADP concentrations to induce maximal aggregation (70 ± 6 vs 23 ±3% n=5, p<0.001) and ATP release ( 2.3 ± 0.7 vs 0.2± 0.1uM n=4, p<0.05). The increased effect of Tpo on ADP-platelet responses was not modified by incubation of platelets with Tpo and G-csf. Flow cytometry studies shown that basal levels of GPIb, GPIIIa and P-selectin were not modified by treatment of platelets with both cytokines alone or in combination (n=5). Loss of GPIb from platelet surface induced by submaximal concentration of thrombin (572±30 vs 308±18 median fluorescence intensity (MFI) n=4p<0.004) was significantly increased by pretreatment of platelets with Tpo, G-csf or both cytokines (308±18 vs 238±19, 264±19 and 251±15 MFI n=4 p<0.004). P-selectin expression induced by thrombin was significantly increased by Tpo (51±4 vs 71±6 % of positive cells n=4 p<0.01 but not by G-csf (51±4%n=4). Incubation of platelets with Tpo and G-csf did not modify the values obtained with Tpo alone (70±4% n=4). Expression of CD11b on PMN surface (195± 15 MFI) was significantly augmented by G-csf (234±21MFI n=5 p<0.01) and FMLP- (236±18 MFI n=5 p<0.01). Tpo was not able to modify either basal levels of CD11b (207± 17 MFI) or the augmented expression induced by G-csf (233±15 MFI n=5 p<0.05). While preincubation of PMN with G-csf increased the effect of FMLP on CD11b expression (293±20 vs 236±18 MFI n=5 p<0.01) Tpo had no effect (244±19MFI n=5). Incubation of Tpo and G-csf gave similar results as those obtained with G-CSF alone (276±19 MFI). While ADP induced 40% of platelet-PMN aggregates formation in whole blood, Tpo and G-csf or the combination of both cytokines did not promote mixed aggregates formation. These data show that in-vitro functional responses of platelets or PMN induced by Tpo and G-csf alone are not further increased nor inhibited by stimulation of the cells with both cytokines.