Tumor necrosis factors alpha and beta differ in their capacities to generate interleukin 1 release from human endothelial cells
Locksley, R.M.; Heinzel, F.P.; Shepard, H.M.; Agosti, J.; Eessalu, T.E.; Aggarwal, B.B.; Harlan, J.M.
Journal of Immunology 139(6): 1891-1895
1987
ISSN/ISBN: 0022-1767 PMID: 3497981 Document Number: 299058
The capacity of the tumor necrosis factors, TNF-.alpha. and TNF-.beta., products of activated macrophages and lymphocytes, respectively, to stimulate interleukin I (IL-1) release from endothelial cells derived from human umbilical veins was examined in vitro. Recombinant TNF-.alpha. caused IL-1 release by 4 hr with maximal levels of 17 U/ml by 24 hr; half-maximal stimulation occurred at approximately 80 pM. In contrast, recombinant TNF-.beta. was a relatively poor stimulus for IL-1 release. Even at concentrations as high as 600 pM, only 3 U of IL-1/ml were recovered; maximal IL-1 release (10 to 12 U/ml) required up to 5 nM TNF-.beta. Natural, glycosated human TNF-.beta. was comparable in activity to recombinant TNF-.beta. TNF-.beta. did not directly inhibit the IL-1 comitogenesis assay, nor was there evidence that TNF-.beta. induced the release of an IL-1 inhibitor, in that supernatants generated in the presence of TNF-.beta. did not inhibit thymocyte proliferation to a recombinant IL-1 standard. Binding of the recombinant TNF to endothelial monolayers was assessed by using [125I]TNF-.alpha. in competition studies with cold TNF-.alpha. and TNF-.beta. Binding of TNF-.alpha. was half-maximal at 80 pM with an average of 664 receptors/cell and Kd = 0.043 nM. Although TNF-.beta. was capable of fully competing for [125I]TNF-.alpha. binding, half-maximal binding occurred at 800 pM TNF-.beta. These data suggest that the TNF receptors on human endothelial cells may reflect the structural differences between these two homologous cytokines.