Endothelial tissue factor induction by T lymphocytes in systemic sclerosis

We evaluated the ability of circulating T lymphocytes obtained from patient s with systemic sclerosis (SSc) to induce the expression of tissue factor ( TF) by human umbilical vein endothelial cells (HUVECs), and compared the re sults with those obtained from healthy controls. Nine patients with SSc and 10 sex- and age-matched healthy subjects were studied. Peripheral T lympho cytes obtained from SSc patients induced TF activity from HUVECs in a dose- dependent manner. A significant induction of endothelial TF was observed wh en 2 x 10(6) lymphocytes per well (TF values, mean +/- SD: 0.34 +/- 0.21 U/ mu g of cell protein vs 0.04 +/- 0.03: n = 9, p = 0.001) or 1 x 10(6) lymph ocytes per well (0.13 +/- 0.06 vs 0.03 +/- 0.04; n = 8, p <0.001) were adde d to HUVEC cultures. Lower concentrations of T lymphocytes were ineffective . Similar results were obtained with control lymphocytes. There were no dif ferences in endothelial TF induction between patients and controls at any l ymphocyte concentration tested. Within the SSc group, there were no correla tions between TF activity and clinical features or disease duration.