Primary Study On The Tumor Evasion Mechanism By The Active Receptor Of NK Cell NKG2D And The Ligand MICA/B In Acute Leukemia Patients

Objective: To value the expression of MICA/B by patients' leukemia cells and the levels of soluble MICA and MICB in sera of patients with acute leukemia.To investigate the expression of NKG2D in peripheral blood of patients with hematopoietic malignancies. To analyze and discuss the function of NKG2D in anti-tumor mechanism and its relation with immune escaping of tumor.Methods: 1. Twenty untreated patients(male/female:13/7) were studied. They were newly diagnosed based on morphologic, immunophenotypic, and cytogenetic criteria. 2. Flow cytometry analysis was used to detect the NK cell active receptor NKG2D and its ligand MICA/B in the peripheral blood of 20 patients with acute leukemia and 5 health persons. 3. We also detected the soluble MICA and MICB levels in sera of these patient and health donors using MICA or MICB-specific enzyme-linked immunosor-bent assay.Results: MICA/B were not expressed or at very low levels on all of the leukemia patients, but they were found at varying levels on the normal lymphocyte with CD45^bright. Sera of the 5 healthy volunteers contained only low levels of MICA and MICB close to the detection limit of the ELISA, they were (5.1±2.8) pg/mL for sMICA and(4. 3±3. 2)pg/mL for sMICB.The levels of sMICA and sMICB from sera of patients with acute leukemia we detecked were (63. 4±45. 7)pg/mL and sMICB(123.5±67. 8) pg/mL respectively, both sMICA and sMICB in patients are significantly higher than the donors(P<0. 0025). The expression of NKG2D on NK cell in leukemia patients and health donors were(79.23± 11.06)% and (93.05±5.72)% respectively.The NKG2D expression in malignant group was significantly low.(P<0.01) Conclusions: MICA/B marked malignant cells for recognition by natural killer(NK)...