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Purpose We performed a prospective study to evaluate the ability of inflammatory cytokines in discriminating gram-negative from gram-positive bacteremia in septic shock. Methods During the study period, the serum inflammatory cytokine levels were measured at the onset of septic shock by flow cytometry in pediatric hematology/oncology patients with septic shock. Results One hundred episodes of septic shock were enrolled. Of 97 episodes of monomicrobial infection, 73.2 % were caused by gram-negative bacteremia and 26.8 % by gram-positive bacteremia. Interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-[alpha] were closely related to the pediatric index of mortality 2 (PIM2) score and mortality. However, although the PIM2 score and mortality were comparable, the IL-6, IL-10, and TNF-[alpha] levels were significantly higher in patients with gram-negative bacteremia (GNB) than those with gram-positive bacteremia (median levels, pg/mL: IL-6: 784.1 vs. 254.4, P = 0.001; IL-10: 192.2 vs. 19.7, P < 0.001; TNF-[alpha]: 4.2 vs. 2.0, P < 0.001). Of the three cytokines, IL-10 was the most useful biomarker for GNB prediction in the derivation cohort and a cutoff value of 50 pg/mL showed a sensitivity of 70.8 % and a specificity of 80.0 %, with a positive predictive value of 89.5 %. When this cutoff value was applied to the validation cohort, the sensitivity, specificity, and positive predictive value were 80.9, 75.0, and 90.5 %, respectively. Conclusions Flow cytometry-based inflammatory cytokine measurement is a helpful adjuvant approach for early and quick discrimination of gram-negative from gram-positive bacteremia in pediatric hematology/oncology patients with septic shock which might be useful for evaluating the severity of shock and the selection and/or timely withdrawal or switch of antibiotics., Author(s): Xiao-Jun Xu [sup.1] [sup.2], Yong-Min Tang [sup.1] [sup.2], Chan Liao [sup.1], Hua Song [sup.1], Shi-Long Yang [sup.1], Wei-Qun Xu [sup.1], Shu-Wen Shi [sup.1], Ning Zhao [sup.1] [sup.2] Author Affiliations: [...]

Objective: To illustrate the diagnostic value of Th1/Th2 cytokine pattern in childhood hemophagocytic lymphohistiocytosis (HLH) and its diagnostic accuracy., Method: The BD(TM) CBA Human Th1/Th2 Cytokine Kit II was used to measure the serum Th1 and Th2 cytokines, including Interferon-gamma (IFN-γ), tumor necrosis factor (TNF), interleukin (IL)-10, IL-6, IL-4 and IL-2 in 50 patients with de novo HLH admitted to our hospital from Oct. 2005 to Aug. 2009. The above cytokine levels were also determined in 250 healthy volunteers and 235 patients with sepsis as controls., Result: The primary features of these patients were prolonged high-grade fever (50/50), hepatomegaly (44/50), splenomegaly (38/50), hemocytopenia (47/50), hyperferritinemia (49/50), coagulopathy (44/50), hemophagocytosis in bone marrow (42/50), liver dysfunction (42/50) and hypertriglyceridemia (42/50). The IFN-γ, TNF, IL-10, IL-6, IL-4 and IL-2 levels for healthy children were (4.6 ± 1.8) ng/L, (4.0 ± 1.2) ng/L, (6.5 ± 1.3) ng/L, (6.0 ± 1.5) ng/L, (2.9 ± 0.8) ng/L and (2.6 ± 0.7) ng/L, while the median levels of them in acute phase of HLH children were 1138.5 (49.2 - 5000.0) ng/L, 3.4 (1.0 - 25.1) ng/L, 740.5 (26.5 - 5000.0) ng/L, 66.1 (3.9 - 4472.6) ng/L, 3.9 (1.0-32.8) ng/L and 4.0 (1.0 - 51.1) ng/L, respectively. The cytokine levels decreased to 9.1 (1.9 - 180.1) ng/L, 2.9 (1.0 - 11.0) ng/L, 11.4 (2.9 - 184.2) ng/L, 6.5 (1.0 - 44.8) ng/L, 2.7 (1.0 - 6.5) ng/L and 4.1 (1.0 - 12.0) ng/L respectively after remission. The IFN-γ, IL-10 and IL-6 levels in acute phase were significantly higher than those after remission and those of the healthy control (P all < 0.001). IL-4, IL-2 and TNF slightly elevated or at normal range in acute phase of HLH. The patients with sepsis showed a different cytokine pattern, with an extremely high level of IL-6 (median: 251.3 ng/L, range: 8.4- > 5000.0 ng/L) and moderately elevated level of IL-10 (median: 46.5 ng/L, range: 3.1 - 5000.0 ng/L), whereas IFN-γ was only slightly elevated (median: 9.2 ng/L, range: 1.3 - 498.8 ng/L). When the criteria for HLH set as the following: IFN-γ > 100 ng/L, IL-10 > 60 ng/L and the concentration of IFN-γ higher than that of IL-6, the specificity reached as high as 98.7% and the sensitivity was 88.0% for the diagnosis of HLH among patients with HLH and sepsis. Meanwhile, the positive predictive value (PPV) and negative predictive value (NPV) could reach 93.6% and 97.5%, respectively., Conclusion: The significant increase of IFN-γ and IL-10 with slightly increased level of IL-6 is a sensitive and specific cytokine pattern for childhood HLH, which is helpful for its diagnosis and differential diagnosis.

Objective: Monitoring of minimal residual disease (MRD) is proven to be increasingly valuable for predicting relapse and outcome of childhood acute lymphoblastic leukemia (ALL) and is used to identify patients' risk groups in several current clinical trials. However, the limitation is that most studies focused on the cut-off value at 10(-4) and the time point after induction. The aim of this study was to investigate the predictive values of different MRD levels detected at different chemotherapy phases in childhood ALL., Methods: One hundred and two patients were enrolled in this study from January 2002 to December 2004 in our hospital. All the patients were treated with modified National Protocol of Childhood ALL in China 1997. MRD levels were detected on the 15th day, 29th day, at 3 months, 6 months and 12 months after initial chemotherapy. All samples were stained with a panel of four colour combinations of fluorochrome conjugated monoclonal antibodies according to the leukemia-associated immunophenotype (LAIP) defined at diagnosis and analyzed by multi-parametric flow cytometry. CD45CD19CD34CD10, CD45CD19CD34CD20 and CD45CD19CD10CD20 were the most common combinations in B lineage ALL, while CD45CD2CD3CD7 and CD45CD2CD3CD34 were the most frequently used immunophenotypes for T lineage ALL. The median follow-up time was 63.3 months ranged from 40.6 to 87.5 months., Results: Of the 102 patients, 64 were male and 38 were female, with a median age of 5.7 (0.2 - 14.8) years. Eighty-eight cases were diagnosed as B lineage ALL and the remaining 14 were T-ALL. The 5-year overall survival (OS) rate and event free survival (EFS) rate for this cohort were (86.9 +/- 3.4)% and (79.9 +/- 4.0)%, respectively. Twelve patients underwent relapse. Among the 102 patients, 14.3% had negative MRD (MRD < 10(-4)) on day 15, 43.9% on day 29, 39.1%, 39.7% and 45.6% had negative MRD at the third, sixth and twelfth month after chemotherapy. Patients who could achieve negative MRD within one year had superior outcome to the others [5-year EFS rates: (92.5 +/- 3.2)% vs. (58.3 +/- 8.6)%, P < 0.001]. The EFS for patients based on MRD levels measured at different stages of therapy were compared by Kaplan-Meier analyses. MRD was predictive of outcome at all 5 time points at a range of thresholds. The optimum threshold, selected for each time point on the basis of log rank analysis, progressively dropped from 10(-2) of day 15 [5-year EFS rates (79.8 +/- 10.3)% vs. (28.6 +/- 17.1)%, P < 0.001], to 10(-3) of day 29 [5-year EFS rates (88.3 +/- 4.9)% vs. (51.3 +/- 14.4)%, P < 0.003], to 10(-4) at 3 [5-year EFS rates (92.4 +/- 5.1)% vs. (65.5 +/- 7.5)%, P < 0.015], 6 [5-year EFS rates (96.3 +/- 3.6)% vs. (65.4 +/- 7.5)%, P < 0.003] and 12 [5-year EFS rates (100.0 +/- 0.0)% vs. (67.7 +/- 8.4)%, P < 0.002] months. And the hazard ratios for relapse and death at higher MRD level groups were 5.91 (95%CI: 1.9 - 18.9), 5.02 (95%CI: 1.5 - 16.5), 5.21 (95%CI: 1.2 - 22.9) and 11.10 (95%CI: 1.5 - 84.5) on day 15, day 29, at month 3 and month 6, respectively. And MRD >or= 10(-2) on day 15 was proven to be an independent predictor by multivariate Cox proportional-hazards regression model., Conclusion: Dynamic MRD detection by multi-parametric flow cytometry is highly predictive of outcome for childhood ALL, and the cut-off values at different time points were different.

Objective: The patients with recurrent or refractory neuroblastoma have a very poor prognosis and high mortality. 10-hydroxycamptothecin (HCPT) is a new agent extracted from comptotheca acuminate, a native plant. It has been shown to be very effective in some solid tumors such as gastric and colon cancers, lung cancers and ovary cancers. However, its efficacy in neuroblastoma has not been determined. This study aimed to investigate the therapeutic effects of HCPT in the treatment of recurrent or refractory neuroblastoma in children., Methods: Ten children with recurrent neuroblastoma and two children with refractory neuroblastoma were treated with HCPT. Of them, 5 children with recurrent neuroblastoma were treated with HCPT alone, and the other 7 patients received combination chemotherapy of HCPT plus other agents. The HCPT alone treatment group was injected with HCPT (7.5 mg/m2 daily) for 14 consecutive days. The combination chemotherapy group was alternately treated with the modified new protocol A1 (cyclophosomide 1 200 mg/m2 on day 1, etoposide 100 mg/m2 on days 1-5, HCPT 5 mg/m2 on days 1-3, cisplatin 90 mg/m2 on day 4) and the modified protocol B (ifosfomide 1.5 g/m2 on days 1-5, HCPT 5 mg/m2 on days 1-3, carboplatin 450 mg/m2 on day 2)., Results: Four patients (33.3%) achieved partial remission and 8 patients (66.7%) had stable disease. The median remission duration was 3.5 months (2-5 months). HCPT treatment as a single agent resulted in mild side effects. Myelosuppression and digestive disorders were found as the main adverse events in the combined chemotherapy group. No chemotherapy related deaths were found., Conclusions: HCPT is safe and effective in the treatment of recurrent or refractory neuroblastoma. The toxicities of HCPT are tolerable. The long-term efficacy of HCPT warrants further research.

Objective: Leukemia is the most common hematopoietic malignancies in children. Chemotherapy is currently the primary modality of treatment for this fatal disease. Although chemotherapy is very effective in terms of cell killing, severe side effects such as severe infections, intracranial hemorrhage etc. are frequently encountered due to its poor selective damage between normal and malignant cells or tissues. Thus, a new therapy with highly selective killing of malignant cells which leaves the normal cells unaffected is desperately desired. The aim of this study was to investigate the targeting efficacy in vitro with a new clone of anti-human CD19 antibody immunotoxin 2E8-Genistein on B lineage leukemia cell line Nalm-6 cells and its mechanisms in order to provide the evidence of target therapy on B lineage leukemia and lymphoma., Methods: 2E8-Genistein immunotoxin was generated by conjugating Mab 2E8 with a tyrosine kinase inhibitor, Genistein (Gen) via the Sulfo-SANPAH, an ultra-violet sensitive reagent. Nalm-6, a CD19+ B cell leukemia cell line, was used as target cells, while Molt-3, a CD19-T cell leukemia cell line, was taken as the negative control. The morphology of the cells was observed under the reverted reversed light microscope and the viability was checked with either trypan blue exclusion or MTT methods. Two-color flow cytometry was applied to study the mechanism of cell killing., Results: After 24 hours of culture, 2E8-Genistein showed marked target killing on Nalm-6 cells at nine different concentrations from 20 nmol/L through 100 nmol/L with cell survival rates from (71.8 +/- 7.9)% down to (16.6 +/- 12.9)%, respectively (n = 3), which were all significantly lower than that of control group (100 +/- 13.9)% (P < 0.05). The killing effect was even more significant when the concentration was over 80 nmol/L. The growth inhibition rates of this immunotoxin on Nalm-6 cells were 82%, 84% and 94%, respectively at 24, 48 and 72 hours of culture in a time dependent manner. Significant difference was observed between the cell growth curve of Nalm-6 cultured with 100 nmol/L of 2E8-Gen and those of Nalm-6 cultured with medium (blank), PBS (negative control) or the same concentration of pure 2E8 antibody (negative control) groups (F = 152.15, P = 2.15 x 10(-7)), but there was no significant difference among the three control groups (F = 1.51, P = 0.29). When Molt-3 cells were used as target cells, the cell growth curves of Molt-3 cultured with 2E8-Gen (100 nmol/L) and with negative control of blank did not show any significant difference (F = 0.34, P = 0.59). PI/FITC Annexin V double staining analysis with flow cytometry showed that the positive rate (33.45 +/- 8.77)% of early apoptosis on Nalm-6 cells induced by 100 nmol/L of 2E8-Genistein was significantly higher than that of negative control of blank (10.44% +/- 1.28%, t = -4.39, P = 0.001) at 24 hours of culture., Conclusion: 2E8-Genistein immunotoxin can significantly target the Nalm-6 cells in vitro in a time response manner and the apoptosis induction is involved in the course of this killing effect.

Objective: Acute promyelocytic leukemia (APL) is a specific type of hematopoietic malignancy, accounting for 10% of the de novo acute myeloid leukemia (AML). The data on long-term outcome of APL in children are limited. The aim of this study was to investigate the clinical biological features, diagnosis, prognosis and long-term survival of childhood APL., Methods: A total of 46 children with newly diagnosed APL from April 1998 to October 2005 were enrolled into this study. Induction treatment containing all-trans retinoic acid (ATRA) plus daunorubicin (DNR) or pirarubicin (THP) was performed on these patients, followed by 6 courses of chemotherapy consolidation: DNR, homoharringtonine or etoposide plus Ara-C. A maintenance therapy was then administered once 3-6 months. The total period of treatment was 2.5 years., Results: Of the 39 patients who had completed the regular treatment, 36 (92.3%) achieved a complete remission. The 5-year cumulative incidence of relapse (CIR) was 28.6%. The estimated overall survival (OS) rates at 1, 3 and 5 years were (86.1 +/- 5.8)%, (76.1 +/- 7.5)% and (70.2 +/- 8.9)% respectively, while the event free survival (EFS) rates were (78.4 +/- 6.8)%, (63.6 +/- 8.7)% and (53.1 +/- 10.0)% respectively. The 5-year OS rate of patients with WBC less than or equal to 10.0 X 10(9)/L was (81.4 +/- 10.3)%, which was significantly higher than that with WBC greater than 10.0 X 10(9)/L[(51.6 +/- 14.7)%, P < 0.05]. Five patients with RT-PCR positive for PML/RARalpha S (short) subtype died eventually although all of them achieved CR, but none of the 13 patients with PML/RARalpha L (long) subtype died., Conclusions: Remission induction therapy with ATRA + DNR or THP is effective and safe for newly diagnosed childhood APL. The remission induction therapy combined with chemotherapy containing high/intermediate dose Ara-C can improve the long-term survival rates of APL patients. High WBC count and S subtype of PML-RARa are two poor prognostic factors for children with APL.

The aim of this study was to evaluate the value of CD117/CD11b phenotypic analysis to diagnosis and prognosis of acute promyelocytic leukemia (APL). Three- or four-color flow cytometry with a series of 22 monoclonal antibodies and CD45/Side Scatter (SSC) gating strategy were used to identify immunophenotypic characteristics of APL as compared to CML in chronic phase (CML-CP). PML/RAR alpha fusion gene was detected by using reverse-transcription polymerase chain reaction (RT-PCR) technique. The results showed that MPO, CD13 and CD33 were almost expressed in all patients with APL and CML-CP whereas HLA-DR and CD34, the hematopoietic progenitor cell markers, were rarely expressed. The positive rate of CD15 in APL was significantly lower than those in CML-CP (P < 0.01). CD117 was positive in 78.3% of the APL cases and in none of the cases of CML-CP. On the other hand, CD11b was almost positive in all cases of CML-CP, but only 16.9% of the APL cases were found positive for this antigen. The CD117+ CD11b- phenotype was present in 72.3% of APL cases while none of cases with CML-CP with this phenotype. Almost all of the cases with CML-CP had the phenotype of CD117- CD11b+. CD117- CD11b+ phenotype was detected in all patients recovering from APL with CD117+ CD11b- phenotype at diagnosis and after treatment with all-trans-retinoic acid (ARTA) for 2 months. PML/RAR alpha fusion gene was positive in 80.6% (25/31) of the APL cases, of which, 64% of the cases belonged to the type L while only 36% of the cases were showed type S for this fusion gene. The positive rates of CD117 were 87.5%, 44.4% and 33.3% in type L group, S group and negative group respectively. It is concluded that analysis of both CD117 and CD11b phenotype may be helpful to the diagnosis, therapy and prognosis of APL in children and adults and to differentiation of APL from recovering benign myeloid proliferation.

Objective: To prepare fluorescein isothiocyanate (FITC) directly conjugated to monoclonal antibody (McAb) anti-human CD14, ZCH-7-2F9 (2F9-FITC)., Methods: After generation and purification, the purity and the murine immunoglobulin subtype of the antibody were evaluated with SDS-PAGE and multicolor flow cytometry (FCM). 2F9 McAb was directly labeled with FITC through modified Marsshall's method and the positive rate of the 2F9-FITC on different types of leukemic cells were compared with the standard CD14-FITC by FCM., Result: A large quantity of purified 2F9 McAb was prepared. The subtype of 2F9 was murine IgG1kappa. 2F9-FITC was successfully manufactured with A295/A280 ratio of 0.44. The positive cell percentages of 2F9-FITC and CD14-FITC on the monocytes were 84.50% and 90.08%, respectively, while those on lymphocytes were only 0.52% and 1.01%. There was no significant difference between the CD14 expressions with 2F9-FITC and CD14-FITC on each type of leukemia (n=23, t=0.922, P=0.367)., Conclusion: 2F9-FITC has been successfully prepared and it can be applied in diagnosis and differentiation of monoblastic leukemias.

Objective: To observe the incidence of elimination delay in high dose methotrexate (HDMTX) therapy, its side effects and influence to next course of chemotherapy and analyze the relationship between the dosage, the duration of MTX infusion and the morbidity of the elimination delay., Methods: A total of 121 childhood acute lymphoblastic leukemia (ALL) (497 infusions of HDMTX) were analysed in this study. The elimination delay rate and the adverse effects in different dose groups (3 g/m2 vs 5 g/m2) and different infusion duration groups (7 h vs 24 h) were compared. The adverse effect evaluation was based on the World Health Organization (WHO) Toxicity Grading Criteria. The rescue dosages of calcium folinate (CF) among these groups were compared through CF/MTX index., Results: The overall morbidity of elimination delay was 12.1% with a relative risk of 30.6% for the first time. The relative risk for the second time of occurrence was increased to 45.9% (P < 0.01) and it was not significantly increased for the third time (35.3%). Children with elimination delay had lower platelet count (P < 0.01) and higher CF rescue dosage (P < 0.01), while the damage of oral mucous membrane was more severe (P < 0.05) and the next course of chemotherapy would be postponed for a median of 4 days in 3 g group. There was no significant difference in elimination delay rates between 3 g and 5 g groups (12.1% vs 12.0%, P > 0.05), and between 7 h and 24 h MTX infusion groups (13.6% vs 11.9%, P > 0.05). The only side effect occurred in 5 g group was gastrointestinal morbidity. The CF/MTX index of 5 g group without elimination delay was less than that of 3 g group (P < 0.01)., Conclusion: Elimination delay in HDMTX therapy accompanies the suppression of bone marrow and damage of oral mucous membrane, which need more CF rescues and will postpone the following course of chemotherapy. Elimination delay is not associated with the duration of the infusion and the dosage of MTX within the range of 3 approximately 5 g/m2 but there are individual differences.

Objective: To define the immune phenotype of colon cancer cells., Methods: Using a panel of 40 anti-human monoclonal antibodies (MoAbs), the cells of colon cancer HR8348 were analyzed with three-color flow cytometry after direct immunofluorescent staining., Results: HR8348 cell line did not express CD2, CD3, CD4, CD5, CD7, CD8, TCR, CD10, CD11b, CD14, CD16, CD19, CD22, CD25, CD28, SmIg, CD33, CD35, CD36, CD41a, CD45, CD45RA, CD45RO, CD56, CD61, CD64, CD66b, CD69, CD71, CD117, CD122 and P-glycoprotein but expressed CD13, CD15, CD20, CD38, CD95 and HLA-DR., Conclusion: The results demonstrate that colon cancer cell line HR8348 shares some antigenic determinants with leucocyte lineage.

Objective: To investigate the expression of CD19 on childhood acute leukemia (AL) and its significance, and to provide evidence for the diagnosis and differential diagnosis as well as monoclonal antibody-targeting treatment of leukemia., Methods: There were 210 cases of childhood AL, of which 130 cases were male and 80 were female with a mean age of 9 years old. Using a panel of 27 fluorochrome directly labeled monoclonal antibodies, 210 samples from the patients were analyzed with CD45/SSC double parameters and multi-color flow cytometry to determine the expression of CD19., Results: In the 93 cases of B lineage acute lymphoblastic leukemia (ALL), the positive rate (98.9%, 92/93) of CD19 was significantly higher than that of the other B cell related antigens, such as CD10 (88.2%, 82/93, P = 0.003), CD20 (24.7%, 23/93, P = 0.001) and CD22 (60.2%, 56/93, P = 0.001). CD19 was expressed on all 8 cases of B/myeloid (My) hybrid acute leukemia (HAL) and 1 case of B/T HAL, but was not expressed on all 24 cases of T lineage leukemia and 5 cases of T/My HAL. In the 79 cases of acute myeloid leukemia (AML), only 5 (6.3%) cases expressed CD19. The positive rate (6.3%) of CD19 on AML was significantly lower than that on B lineage ALL (98.9%, P = 0.001). The percentage of CD19 positive cells in B/My HAL (41.6% - 88.7% with a mean of 73.8%) was significant higher than that in CD19(+)-AML (21.4% - 50.4% with a mean of 24.2%; Run Sum test, P = 0.0084). Of the 210 cases, 102 were B lineage related AL including B lineage ALL, B/My HAL and B/T HAL. In B lineage related AL, the sensitivity and the specificity of CD19 was 99.0% (101/102) and 95.4% (13/108) while the positive predictive and the negative predictive values to B lineage were 95.3% (101/106) and 99.0% (103/104), respectively. Using CD19(+) as a single reagent to diagnose B lineage, the false positive rate was 4.6% (5/108) and the false negative rate was 1.0% (1/102) with a general diagnosis index (GDI) of 94.4% [GDI = 1-(false positive rate + false negative rate)]., Conclusion: CD19 is continuously and stably expressed on all stages of B lineage differentiation. It is a reliable cell membrane marker for diagnosing B lineage ALL and an ideal target for antibody-targeting treatment of leukemia as well; the expression degree of CD19 can be used to distinguish B/My HAL from CD19(+)-AML; CD19 didn't express on normal myeloid cells but did on some AML cells. Therefore it can be used to detect the minimal residual disease.

Objective: To explore the expression of CD(117) on different types of leukemia and its significance., Methods: CD(117) expression was analysed by three-color flow cytometry with CD(45)/SSC gating strategy., Results: CD(117) was expressed in 68% of acute myeloid leukemia (AML) and 80% of chronic myeloid leukemia in blast crisis (CML-BC) cases, but in only 2% of acute lymphoblastic leukemia cases. CD(117) was negative in CML in chronic phase and chronic lymphocytic leukemia. Cases in AML, CD(117) was expressed in 72% of M(0)/M(1), 88% of M(2), 50% of M(4), 75% of M(5a), 100% of M(6) and 100% of M(7) cases but was less expressed in M(3) (39%) and M(5b) (29%) cases. Expression of CD(117) was more frequent than CD(34) and HLA-DR in M(3) and some M(2) cases. There was a significant inverse relationship between CD(117) and CD(14) expression in AML., Conclusions: Analysis of CD(117) expression may be of help in distinguishing myeloid from lymphoid leukemia and leukemia clone from normal cells.

Objective: Acute leukemia (AL) is one of the most common malignant diseases in children. AL immunophenotypes are known to be benefit to the predictable prognoses and specific therapy. Recently, the accuracy of AL immunophenotyping was dramatically improved with the application of the flow cytometry, the new monoclonal antibodies, the improvement of the gating strategies and the multi-parameter analytic techniques. The aim of this study was to evaluate the value of multi-color flow cytometry in the immunophenotyping of acute leukemia in children., Methods: Three- or four-color flow cytometry and CD(45)/Side Scatter (SSC) gating were used to analyze the surface and cytoplasmic (Cy) antigen expressions in 222 successive cases of childhood acute leukemia., Results: Cells from 222 cases of children with acute leukemia were analyzed. Based on the diagnostic criterion proposed by European Group for the Immunological Characterization of Leukemia (EGIL), four categories could be identified: the undifferentiated type accounted for 0.9%, acute myeloid leukemia (AML) 35.1%, acute lymphoblastic leukemia (ALL) 55.9%, and mixed lineage AL 8.1%. Of 124 patients with ALL, 94 patients (75.8%) were classified as B lineage and 30 patients (24.2%) T lineage ALL. Antigen aberrant expressions were found in AML (24.4%), B lineage ALL (36.2%) and T lineage ALL (30.0%). CD(7) was the most commonly expressed lymphoid antigen in AML (12.8%), followed by CD(19) (6.4%) and CD(2) (5.1%). CD(13) was the most commonly expressed myeloid antigen in ALL (18.5%), followed by CD(15) (11.3%), CD(11b) (6.5%) and CD(33) (4.3%). CD(117) and CD(56) presented in 73.3% and 38.0% cases of AML, respectively, but were generally absent on blast cells of ALL. CyCD(22), CyCD(3) and CyMPO were specifically expressed in B lineage, T lineage and myeloid lineage leukemia, respectively, and the first two could be more sensitively detected than they were on cell membrane surface., Conclusions: Multi-color flow cytometry is a reliable technique in the diagnosis, differential diagnosis and classification of acute leukemia in children.