Cleaved L-Selectin in acute leukemia

ABSTRACT

L-selectin plays a critical role in the initiation of normal leukocyte attachment to activated endothelium, whereas other receptors [including integrins and immunoglobulin-like adhesion molecules] are involved in leukocyte subsequent firm adhesion and transmigration into tissues. Soluble L-selectin retains bioactivity, and at high concentrations can inhibit binding of lymphocytes to endothelium. Little information is yet available on the diagnostic and physiologic significance of the circulating shed form of L-selectin. The present work was designated to measure sL-selectin levels during the clinical course of patients with acute leukemia. Serum samples were obtained from 59 patients with newly diagnosed acute leukemia, including 37 patients with AML and 22 patients ALL. The diagnosis and classification of AML or ALL were based on the criteria of the French-American-British Cooperative Group and immunophenotyping. Additional samples were obtained from patients in complete remission and patients after relapse. Control serum samples were obtained from 15 healthy blood donors. Serum samples were separated immediately and kept frozen at -20°C until assay. Leukemic patients were treated according to standard protocols for AML or ALL. Immunophenotyping was done on mononuclear cells separated on Ficoll-Hypaque. Cell surface antigens were detected by standard immunoflurescence methods using flowcytometer. Shed L-selectin assay was done using a sandwich immunoenzymometric technique. This study shows high levels of the sL-selectin in serum of patients with acute leukemia. The mean value of sL-selectin among healthy individuals was 1.120 +/- 0.178 micro g/ml. This value was increased in 17 of 22 patients with ALL [77%] and 25 of 37 patients with AML [65.5%]. Repeated measurements in 24 patients showed normal range in 19 patients with complete remission and high levels in 5 patients with therapy resistant acute leukemia. There are also increased levels in patients with relapse. High levels of serum sL-selectin in patients with acute leukemia may have an important role in regulating the initiation of blast cell adhesion to endothelium. In addition, measuring sL-selectin may be useful in detection of leukemia relapse. However, further in vivo studies are needed to establish definitely the role of sL-selectin in the regulation of blast cell migration into tissues