[The Establishment and Identification of Acute Myeloid Leukemia NOD-SCID-IL2rg-/-Mice Model by Using Luciferase-Expressing KG1a Cells].

OBJECTIVE: To establish the in vivo traceable acute myeloid leukemia mice model with Luciferase-Expressing KG1a Cells. METHODS: KG1a cells with stable luciferase gene expression (called as KG1a-Luc cells) were constructed by lentivirus transfection, then sifted out by puromycin. Eighteen male NOD-SCID-IL2rg-/-mice aged 8 to 12 weeks were randomly and equally divided into two groups: the control group and the KG1a-Luc group. The mice in KG1a-Luc group were injected with 200 µl PBS containing 5×106 KG1a-Luc cells through tail veins, and the mice in control group were injected with 200 µl PBS only. The bioluminescence imaging technology was used to monitor the tumor burden in vivo. The peripheral blood of the mice in both groups was analyzed by flow cytometry. After the mice were sacrificed, there were pathologic evaluations: bone marrow and spleens made into smears, and livers sliced to get paraffin sections. The survival time of the mice in the two groups was recorded and compared. RESULTS: KG1a cells expressing luciferase stably were successfully obtained. The tumor luminescence wildly spread at day 17 captured by in vivo imaging. The KG1a-Luc tumor cells could be detected in the peripheral blood of the mice, with the average percentage of (16.27±6.66)%. The morphology and pathology result showed that KG1a-Luc cells infiltrate was detected in bone marrow, spleens and livers. The survival time of the KG1a-Luc mice was notably shorter as compared with those in the control group, the median survival time was 30.5 days (95%CI: 0.008-0.260). CONCLUSION: The acute myeloid leukemia NOD-SCID-IL2rg-/-mouse model was successfully established by tail vein injection of 5×106 KG1a-Luc cells.

[Expression and Significance of BTLA and Its Ligand HVEM in Patients with Chronic Myelomonocytic Leukemia].

OBJECTIVE: To investigate the expression and significance of B and T lymphocyte weakening factor (BTLA) in patients with chronic myelomonocytic leukemia (CMML). METHODS: Real-time PCR was used to detect the expression of BTLA and its ligand HVEM mRNA in 11 patients with chronic myelomonocytic leukemia and 11 normal donors. Flow cytometry was used to detect expression of BTLA and its HVEM on the cell surface of peripheral blood T lymphocytes and γδ T cells. RESULTS: The median values of BTLA and its ligand HVEM mRNA expression in peripheral blood of patients with CMML were 0.009% and 559.4%, respectively, which were significantly lower than those of normal controls (0.053% and 1031%)(P<0.001). The expression level of BTLA and HVEM on cell surface of peripheral lymphocytes was not significantly different from that in normal controls (P=0.3031 and 0.2576), however, the proportion of peripheral blood T lymphocytes in patients with CMML (median: 37.73%) was significantly lower than that in controls (median 69.23%)(P=0.0005). The expression of BTLA on the surface of γδ T cells in peripheral blood of patients with CMML (median: 23.26%) was significantly lower than that of the controls (median: 52.64%) (P<0.05), and there was no significant abnormality in HVEM expression (P=0.2791). CONCLUSION: The expression of BTLA and its ligand HVEM, the proportion of T lymphocytes and the expression of BTLA on the surface of γδ T cells in patients with CMML are reduced. The effects of these abnormalities on T cell function and prognosis and efficacy of patients need to be further observed.

[Regulatory Effect of Exosomes Derived from Human Umbiilcal Cord Mesenchymal Stem Cells on Treg and TH17 Cells].

OBJECTIVE: To investigate the effects of exosomes from human umbilical cord mesenchymal stem cells on the development of Treg and TH17 cells. METHODS: Exosomes from the serum-free-culture supernatants of hUC-MSC were harvested by ultracentrifugation. The electron microscopy, nanoparticle tracking analysis and western blot were used to identify the hUC-MSC-exosomes, such as the morphology, the paticle chameter, and the protein content. The PBMC stimulated with anti-CD3/CD28 were incubated with the exosomes for five days, and then the percentage changes of Treg and TH17 cells were analyzed by using flow cytometry. RESULTS: The hUC MSC-derived exosomes were saucer-like in morphology the averge diameter was approximately 142 nm. They were identified as positive for CD9 and CD63. Flow cytometry showed that the proportion of CD4+CD25+Foxp3+ Treg cells in the PBMC were significantly higher, but the proportion of CD4+IL17A+ T cells in the hUC-MSC-exosome group was obviously lower than that in the group without the hUC-MSC-exosom (control group) (P<0.05). CONCLUSION: The hUC-MSC-exosomes have an immunomodulatory effect on T cells in vitro by increasing the ratio of Treg and reducing the ratio of TH17 cells, expecting the hUC-MSC-exosom as a novel cell-free target for immunotherapy.

[JAK3 mRNA level in graft versus host disease patients: a preliminary study].

OBJECTIVE: To quantify peripheral blood mononuclear cell JAK3 mRNA levels after allogeneic haematopoietic stem cell (allo-HSCT) transplantation, and to explore its relationship with graft vs host disease (GVHD). METHODS: Serial monitoring of JAK3 mRNA levels by fluorescent quantitative reverse transcriptase polymerase chain reaction (FQ-RT-PCR) technique was performed on 26 cases (83 samples) after allo-HSCT. RESULTS: The mean JAK3/ABL expression levels was 8.71 in 14 patients without GVHD; the JAK3/ABL expression level was 31.94 in one patient with acute GVHD (aGVHD); the mean JAK3/ABL expression levels was 19.23 in 11 patients with chronic GVHD (cGVHD), and the cGVHD was diagnosed at the mean time of six months (3 - 12 months). The JAK3/ABL expression levels did not change in 4 patients one month after allo-HSCT, however, the levels increased again when GVHD were diagnosed in these 4 patients, and the JAK3/ABL expression levels decreased again when GVHD was remitted. CONCLUSION: The JAK3 expression level related to the remission and relapse in patients with GVHD.

[C-kit mutation in acute myeloid leukemia patients with AML1-ETO fusion gene and its clinical significance].

This study was aimed to investigate the c-kit mutation in acute myeloid leukemia (AML) patients with AML1-ETO and analyze its relation with clinical and laboratorial features and prognosis. PCR and sequencing methods were used to detect the c-kit 17 exon mutations in 31 AML patients with AML1-ETO. The relation of the c-kit mutation with clinical features, results of laboratorial examination and prognosis of disease were analyzed. The results showed that the c-kit mutation was found in 14 out of 31 AML patients and the mutation frequency was 45.16%. Male patients had a higher incidence of c-kit mutation than that of female patients (P = 0.020). The proportion of patients with newly diagnosed white blood cell>10×10(9)/L and with extramedullary infiltration in mutated group were higher than those in unmutated group respectively. No significant difference was observed at the age (P = 0.437) and the rate of bone marrow blasts(P = 0.510) between the above mentioned two groups. The difference in complete remission rate (64.29% vs 80%, P = 0.344)and relapse rate (58.33% vs 21.43%, P = 0.054) between c-kit mutated and c-kit unmutated groups were not significant. While the c-kit mutated group had a significant higher death rate as compared with c-kit unmutated group (57.14% vs 20%, P = 0.039). It is concluded that the c-kit mutation is frequent in AML patients with AML1-ETO and the c-kit mutated patients have a poor prognosis. It is important to detect c-kit mutation in routine clinical practice for patient's risk stratification, evaluation of prognosis and selection of effective treatment.

[Predictive value of molecular response after treatment with tyrosine kinase inhibitor for 3 months in patients with chronic myeloid leukemia].

OBJECTIVE: To understand the predictive value of early monitoring BCR-ABL transcripts in patients with chronic myeloid leukemia (CML) after treatment with tyrosine kinase inhibitor (TKI), and to provides the information for early assessment of prognosis and treatment options. METHODS: BCR-ABL transcripts of 53 CML patients before and after TKI treatment were detected by using real-time quantitative RT-PCR. The relationship between BCR-ABL transcripts level after TKI treatment for 3 months and the later molecular response, progression and mutation was analyzed. RESULTS: The median values of BCR-ABL transcripts in peripheral blood samples from 30 newly diagnosed patients were 43.99%, which was used as a baseline of BCR-ABL transcripts for molecular response evaluation. Of 53 patients, 31 (58.49%) had a BCR-ABL mRNA ≤ 4.40% (reduced more than 1 log) and 22 (41.51%) greater than 4.40% (reduced to less than 1 log) after 3 months of TKI treatment. The former 31 patients had a significantly higher 18-months cumulative incidence of major molecular response (MMR) (90.32% vs 18.18%, P=0.000) and 3-year cumulative incidence of complete molecular response (CMR) (48.39% vs 0, P=0.000) compared with the latter 22 patients. The lower BCR-ABL level was, the earlier MMR reached. The proportion of patients with a mutation in group of BCR-ABL mRNA>4.40% was significantly higher than that of BCR-ABL mRNA ≤ 4.40% (22.73% vs 0, P=0.021). The incidence of progression increased in group of BCR-ABL mRNA>4.40%, but the difference was not statistically significant (P=0.052). CONCLUSION: It is important for the prognosis evaluation of the patients to monitor the level of BCR-ABL transcripts at 3 months after TKI treatment, which might help to early optimization of treatment and to improve curative effect of CML patients.

[A multicenter comparison study on the quantitative detection of bcr-abl (P210) transcript levels in China].

OBJECTIVE: To investigate the comparability of bcr-abl (P210) transcript levels detected in different hospitals. METHODS: Ten hospitals in China took part in the four times of sample exchange and comparisons from April, 2010 to August, 2011. The exchange samples were prepared by Peking University People's Hospital. Firstly, the BCR-ABL (P210)(+) cells from a newly diagnosed chronic myeloid leukemia patient were 10-fold serially diluted by BCR-ABL (P210)(-) cells and they covered 4 magnitudes. Then, TRIzol reagents were thoroughly mixed with cells in each tube. Every 12 samples (three samples per magnitude) were sent to the other 9 hospitals. The cell number of each sample was 8×10(6). The detection of bcr-abl transcript levels by real-time quantitative PCR were performed in every hospital according to their own protocols. Conversion factors (CF) were calculated using regression equation. RESULTS: Differences in bcr-abl transcript levels did exist among results of 10 hospitals in each comparison. In general, the results of the most of hospitals were in line with the dilutions of cells. CF of every hospital fluctuated. Three hospitals had relatively stable CF, and their ranges were 2.8 - 5.2, 1.2 - 2.8 and 2.2 - 6.8, respectively; two hospitals had unstable CF with ranges 0.76 - 7.0 and 2.1 - 18.7; three hospitals couldn't be calculated CF one or two times because of the significant deviation of the results from the actually bcr-abl transcript levels, and their ranges of CF which could be calculated were 1.9 - 19.2, 3.6 - 7.6 and 0.18 - 14.7; One hospital only had two CF (3.3 and 5.0) because of the replacement of an important reagent during the period of comparisons. CONCLUSIONS: Comparability of bcr-abl (P210) transcript levels between different hospitals could be achieved through CF which acquired by sample exchange and comparison. The stable and reliable detection system is the premise to acquire correct CF.

[A method for induction of mouse CD8α(+);CD11b(+);jagged2(high);regulatory dendritic cells with mesenchymal stem cells in vitro].

AIM: To develop a method for induction of the mouse bone marrow-derived CD8α(+);CD11b(+);jagged2(high);regulatory dendritic cells (DCregs) using mesenchymal stem cells (MSCs) in vitro. METHODS: BALB/c(H-2(d);)mouse bone marrow cells (BMCs) were isolated and induced to CD8α(+);CD11c(+);CD11b(+);DCs (DCs) by 4 cytokines in vitro for 3 d. The DCs were selected by flow cytometry (FCM), and co-cultured with MSCs for 10 d to get DCregs. Immunophenotypes, cell cycle, Jagged1 and Jagged2 ligands of the Notch pathway of DCs were analyzed by FCM before and after co-culture. RESULTS: The novel DCs were transformed into DCregs successfully. The expressions of CD86, CD80, CD40, and MHC-II significantly decreased (P<0.05), while those of CD205, Jagged1 and Jagged2 obviously increased on DCregs (P<0.05). Meanwhile, the percentage of treated MSCs cells went up in G2 and S phases. CONCLUSION: MSCs co-cultured with DCs can induce the development of DCregs, which have immune tolerance-associated phenotypes and higher proliferation ability. This mechanism might be related to the up-regulated Jagged1 and Jagged2 expressions and the T-cell Notch pathway activation.

[Expression of CD133 in the bone marrow of patients with myelodysplastic syndrome and its clinical significance].

OBJECTIVE: To investigate the expression of CD133 in the bone marrow of patients with myelodysplastic syndrome (MDS) and explore its clinical significance. METHODS: The expression of CD133 and CD34/CD38 in the bone marrow was detected using flow cytometry in 31 cases of refractory anemia with excess blasts (RAEB), 10 cases of refractory cytopenia with multilineage dysplasia (RCMD) and 11 cases of aplastic anemia (AA). RESULTS: The percentage of CD133-expressing cells was 6.75% in patients with RAEB, significantly higher than that in patients with RCMD (1.41%) and AA (2.70%) (P<0.05); the percentage of CD133-positive cells were similar between the latter two patient groups (P>0.05). The percentage of CD34(+)/CD38- cells was similar in the 3 groups (P>0.05), all lower than 1%. CONCLUSIONS: Advanced MDS patients are characterized by an increase of CD133-expressing cells, suggesting the value of CD133 in the diagnosis of RAEB. CD34(+)/CD38- cells do not show a significant value in the diagnosis of MDS.

[Detection of methylation levels of multi-genes by real-time PCR in patients with myelodysplastic syndrome].

OBJECTIVE: To analyze the promoter methylation levels of p15, CDH1, DAPK and HICI genes of patients with myelodysplastic syndrome (MDS) and explore the relationship between the level of methylation and clinical features. METHODS: DNA methylation levels of p15, CDH1, DAPK and HICI in peripheral blood (PB) or bone marrow (BM) samples from 52 MDS patients were detected by real-time quantitative PCR. The correlation of the methylation level with clinical features and hematological findings was analyzed. 38 de novo AML patients and 46 normal individuals served as controls. RESULTS: The methylation levels of p15, CDH1, DAPK and HICI were 16.23 ± 21.69, 6.59 ± 9.39, 0.14 ± 0.11 and 7.81 ± 9.70 in BM, and 14.96 ± 20.16, 6.00 ± 9.26, 0.12 ± 0.14 and 6.74 ± 9.72 in PB, respectively from 18 MDS patients, and the difference between BM and PB was not statistically significant (P > 0.05). The methylation levels of p15 (14.70 ± 18.17) and CDH1 (6.61 ± 8.79) genes in high risk (RAEBI/II) MDS were significantly higher than in low risk (RCMD/RARS/5q-, p15: 1.99 ± 1.59, CDH1: 1.23 ± 1.14 and RCMD, p15: 3.02 ± 3.42, CDH1:1.53 ± 2.06) MDS or control (p15: 1.69 ± 1.82, CDH1: 1.01 ± 1.12) (P < 0.05). The methylation levels of DAPK gene had no difference among subtypes of MDS, and that of HIC1 gene only differed between RAEB I/II (9.16 ± 11.95) and control (2.49 ± 2.26) (P = 0.042). The difference of methylation levels of p15, CDH1, DAPK and HICI in BM was statistically significant among subtypes of MDS (P = 0.001, 0.003, 0.039, 0.023, respectively). And so did of p15 and DAPK in PB (P = 0.013, 0.006, respectively). The methylation level of p15 and CDH1 was significantly correlated with IPSS classification and blasts percentage in BM. CONCLUSIONS: p15 and CDH1 genes are special hypermethylation genes in MDS. Methylation level of HIC1 gene showed an upward tendency from low risk to high risk MDS.

[Expression of antiapoptotic gene aven in de novo acute myeloid leukemia patients and its clinical significance].

This study was aimed to investigate the aven mRNA expression level of leukocytes from peripheral blood(PB)of de novo patients with acute myeloid leukemia (AML) and analyze its clinical significance, so as to provide a experimental basis for evaluating prognosis. The aven mRNA expression levels in PB samples from 69 de novo AML patients were detected by using real-time quantitative PCR. The relation of aven mRNA level with clinical and hematological characteristics (age, sex, WBC, Hb, Plt, LDH, Blast% in PB and BM, FAB subtype) and treatment outcome (CR rate and relapse rate) were analyzed. 21 normal individuals served as controls. The results showed that the expression level of aven mRNA was between 11.72% and 178.93% (median 37.2%) in de novo AML and between 10.81% and 50.98% (median 28.81%) in normal individuals. Aven mRNA expression level was higher in the AML group than that in the controls (p = 0.006). As aven mRNA expression level was compared with other clinical and hematological parameters, there were significant correlations between aven mRNA expression level and age (r = 0.25, p = 0.039), and between hemoglobin level (r = 0.29, p = 0.019), FAB subtype(r = 0.253, p = 0.036). The median expression level (50.08%) of aven mRNA in older patients (> or = 44 years) was higher then that (32.41%) in younger patients (< 44 years) (p = 0.018). The complete remission (CR) rate after two cycles of chemotherapy in patients with lower aven mRNA level (25/30, 83.33%) was higher than that in patients with higher aven mRNA level(21/30, 70%), but the difference was not significant(p = 0.22). The difference of aven mRNA expression level between AML patients with relapse and AML patents without relapse was not significant (p = 0.076). It is concluded that the expression level of aven mRNA in de novo AML patients obviously increases, the overexpression of aven mRNA likely involves in genesis of AML. The definite relation of aven mRNA expression level with treatment outcome and relapse was not been found.

[Role of nitro oxide in immunosuppressive effect of human mesenchymal stem cells on allogenic proliferative response of lymphocytes].

The purpose of this study was to investigate the influence of nitro oxide (NO) from mesenchymal stem cells (MSC) on the proliferative responses of allogeneic lymphocytes and its mechanism. MSCs were isolated and cultured from human bone marrow. Selected surface antigens of MSCs were detected by flow cytometry and their morphologic characteristics were determined by microscopy. Mitomycin C-treated MSCs were plated in dishes and then mixed lymphocyte cultures (MLC) were set up. After 4 days, lymphocyte proliferation was determined by CCK-8 assays; NO secretion in coculture supernatant was determined by Griess reagent kit; the level of FOXP3 mRNA expression was detected by real-time quantitative PCR. The results indicated that in MSC/MLC coculture experiment, the lymphocyte proliferation decreased significantly with of IOD value 0.49+/-0.03, NO production increased obviously (21.05+/-1.14 micromol/L) and FOXP3 mRNA expression was increased [(1.56+/-0.34)%] as compared with MLC coculture without MSC. There were significant difference between these two groups. It is concluded that NO production in human MSC culture up-regulates FOXP3 mRNA expression and thus inhibits lymphocyte proliferation response.

[Serum proteomics in patients with RAEB myelodysplastic syndromes].

OBJECTIVE: To screen the molecular markers for refractory anemia with excess blasts in transformation (RAEB) in myelodysplastic syndromes (MDS) by serum proteome profiling. METHODS: The serum protein were isolated from patients with RAEB, acute myeloid leukemia or normal subjects by 2-dimensional electrophoresis (2-DE), and the electrophoresis gels were obtained to identify the differentially reacting protein spots. The replica gels of the differentially reacting proteins were analyzed to locate the matching protein spots, which were identified by peptide mass fingerprint based on matrix-assisted laser desorption/ionization time of-flight mass spectrometry (MALDI-TOF-MS) and database searching. RESULTS: Seven differentially expressed proteins in RAEB were found by 2-DE. Of the 7 proteins, 4 were identified by MALDI-TOF-MS to have significantly differential expression in RAEB, including dipeptidyl peptidase (DPP/CD26), polymerase (DNA directed) kappa, PRO2044 and an albumin-like protein. CONCLUSION: 2-DE-based serum proteome profiling helps identify serum proteomic biomarkers related to MDS. DDP/CD26 has increased expression in the serum in RAEB subtype MDS, suggesting its possible role in advanced MDS.

[Relationship between thymus output function in CML patients and their bcr-abl mRNA levels].

The study was purposed to analyze the relationship between the content of T-cell receptor excision DNA circles (TREC) and bcr-abl mRNA levels in CML patients and to evaluate the prognostic significance of recent thymic output function detection in patients with chronic myelogenous leukemia (CML). Quantitative detection of TREC and bcr-abl fusion gene transcripts in peripheral blood from 15 CML patients were preformed by real-time PCR. The change of bcr-abl levels in 6 patients was followed-up for two years. The results showed that there was no significant correlation between TREC and bcr-abl mRNA levels in peripheral blood from CML patients for the first attack. Patients who had higher TREC at diagnosis had a larger reduction of bcr-abl after 2 years of follow-up. While out of 2 patients who underwent haemopoietic stem cell transplantation (HSCT), one patient with higher level of TREC before transplantation was confirmed to express undetectable level of TREC by three consecutive detections after transplantation, other one patient was identified to express low level of bcr-abl. It is concluded that high thymic output function in CML patients can be beneficial for killing the residual CML cells.

[Significance of quantitative detection of bcr-abl mRNA in chronic myeloid leukemia patients after allogeneic hematopoietic stem cell transplant].

The objective of this study was to analyze the level of bcr-abl mRNA in peripheral blood (PB) after allogeneic stem cell transplantation (allo-SCT) in chronic myeloid leukemia patients, providing a experimental basis for diagnosing early relapse. bcr-abl mRNA levels in 78 PB and bone marrow (BM) samples from 15 CML patients after allo-SCT were detected by using real-time quantitative PCR. The results indicated that levels of bcr-abl mRNA before transplantation were high (median 29.303%) and decreased greatly (median 0) at the first month after allo-SCT. During the first year after allo-SCT, the patterns of serial bcr-abl transcripts varied in number, but the overall bcr-abl transcript levels significantly decreased at 6 months after allo-SCT. Majority of patients with undetectable or very low levels of bcr-abl mRNA were monitored after 1 year following transplantation. The hematological features of BM and PB in all detected patients remained normal. PB and BM bcr-abl values were not different significantly and had the similar trend of changes. It is concluded that the bcr-abl mRNA levels in CML patients change greatly early after allograft. Serial monitoring measurements for bcr-abl mRNA contribute to understanding the trend of change and effect of transplantation, also can be a guidance for starting therapy. But detectable levels of bcr-abl mRNA during the first 6 months do not indicate relapse. Measurements of bcr-abl mRNA of PB may be more suitable for routine monitoring long-term disease status in CML after allo-HSCT.

[Thymic recent output function in patients with B-cell lymphocytic malignancies].

The aim of the study was to analyze the naive T cell level of thymic recent output in patients with B-cell malignancies, thereby to evaluate the potential T-cell function. Quantitative analysis of T-cell receptor rearrangement excision circles (TRECs) in DNA of peripheral blood mononuclear cells from 61 cases of B-cell lymphocytic malignancy (including 20 cases of adult B-ALL, 6 case of childhood B-ALL, 4 cases of B-CLL, 17 cases of B-NHL and 14 cases of MM) were preformed by real-time PCR (TaqMan), and TREC-level was detected according to the number of CD3-positive cells. 5 case of ALL-CR and 17 normal individuals were served as controls. The results showed a dramatic reduction of TREC values in all groups of patients. The mean value of TRECs was 0.53 +/- 1.52 copies/1000 PBMNC and 2.01 +/- 3.93 copies/1000 CD3+ cells in adult B-ALL (p = 0.0005, p = 0.0123), 0.11 +/- 0.15 copies/1000 PBMNC and 0.23 +/- 0.27 copies/1000 CD3+ cells in B-CLL (p = 0.0015, p = 0.0381), 0.71 +/- 1.34 copies/1000 PBMNC in B-NHL (p = 0.0017), 0.53 +/- 0.90 copies/1000 PBMNC in MM patients (p = 0.0018), as compared with 3.76 +/- 3.42 copies/1000 PBMNC and 5.87 +/- 4.96 copies/1000 CD3+ cells in normal individuals, the TREC level was significantly decreased in all groups of B-cell lymphocytic malignancy, as well as in ALL-CR group. However, the TREC level in childhood B-ALL was significant higher than those in adult B-ALL group. It is concluded that the function of thymic recent outputting naive T cells in B-cell malignancies significantly decreases, however, the individual difference of thymic output function is obvious. The thymic recent output function can not be recovered during CR phase in patients with B-cell malignancies, so that dynamic analysis of TREC level is necessary.

[Peripheral blood naive T cell level and its T cell receptor Vbeta repertoire usage profile in patients with chronic myelogenous leukemia].

OBJECTIVE: To analyze peripheral blood naive T cell level, its T cell receptor (TCR) Vbeta repertoire usage profile and clonality for evaluating the recent thymic output function and the expansion feature of TCR Vbeta subfamily T cells in patients with chronic myelogenous leukemia (CML). METHODS: Quantitative detection of T-cell receptor excision DNA circles (TRECs) in peripheral blood mononuclear cells (PBMNC) from 20 cases of CML was preformed by real-time PCR (TaqMan) analysis, and TRECs-number in T-cells was calculated from peripheral blood CD3-positive cell rate. The expression and clonality analysis were detected by RT-PCR and Genescan technique in PBMNC from 14 out of the 20 patients. Nine normal individuals served as controls. RESULTS: A dramatic reduction of TRECs value in patients with CML was detected as compared with that in normal controls. The mean value of TRECs was 0.06 +/- 0.16 copy/1000 CD3(+) cells in CML patients while 6.84 +/- 4.71 copies/1000 CD3(+) cells in normal controls (P < 0.01). The 1 - 12 Vbeta subfamilies were variably expressed in samples from 14 patients. Genescan analysis identified clonal expanded T cells of some Vbeta subfamily from 13 cases. Vbeta3, Vbeta10, Vbeta19, Vbeta21 and Vbeta22 subfamilies clonal T cells were more frequently seen. CONCLUSION: There is a prominent reduction of recent thymic output naive T cells function in CML. The predominant usage and clonal expansion of TCR Vbeta subfamily T cells could be identified, indicating that CML patients have specific immune response to leukemia associated antigen, in spite of their T cell immunodeficiency.