Prothymosin α1 Effects on IL-2-Induced Expression of LFA-1 on Lymphocytes and Their Adhesion to Human Umbilical Vein Endothelial Cells

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Abstract
Prothymosin α1 (Pro α) is known to stimulate in vitro and in vivo natural killer (NK) and lymphokine (IL-2)-activated killer (LAK) cells against tumor cells. In this process, LAK cells first adhere to endothelial cells in vivo, raising the question whether Pro α1 affects this interaction as well. The binding ability of peripheral blood lymphocytes (PBL) to human umbilical vein endothelial cells (HUVEC) was increased by incubation with IL-2 in a concentration-dependent manner, reaching a maximal value at 20Uml IL-2. Although Pro α1 alone was without any stimulating effect, it significantly increased PBL binding to unstimulated HUVECs in combination with suboptimal IL-2 (5 and 10 U/ml). The combination of Pro α1(1 µg/ml) and 5 U/ml or 10 U/ml IL-2 is as effective as 10 U/ml or 20 U/ml IL-2 alone. This Pro α1 effect on IL-2-activated lymphocytes was found to be augmented on IL-1 or tumor necrosis factor (TNF)-α-activated endothelial cells. Analyzing the effect of Pro α1 on IL-2-activated lymphocytes by flow cytometry revealed an increase of CD16, CD56, and CD18 surface marker expression, whereas CD3, CDlla/b, CD49d, and CD54 were not affected. In conclusion, Pro α1 functions as a mediator of the adhesion of IL-2-activated lymphocytes to HUVECs.

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