Advanced flow cytometry for biomedical applications

Flow cytometry (FC) is a versatile tool with excellent capabilities to detect and measure multiple characteristics of a population of cells or particles. Notable advancements in in vivo photoacoustic FC, coherent Raman FC, microfluidic FC, and so on, have been achieved in the last two decades, which endows FC with new functions and expands its applications in basic research and clinical practice. Advanced FC broadens the tools available to researchers to conduct research involving cancer detection, microbiology (COVID-19, HIV, bacteria, etc.), and nucleic acid analysis. This review presents an overall picture of advanced flow cytometers and provides not only a clear understanding of their mechanisms but also new insights into their practical applications. We identify the latest trends in this area and aim to raise awareness of advanced techniques of FC. We hope this review expands the applications of FC and accelerates its clinical translation.

CD34 negative HLA-DR negative acute myeloid leukaemia: A higher association with NPM1 and FLT3-ITD mutations

INTRODUCTION

CD34 and HLA-DR negativity is often used as a characteristic immunophenotypic feature of acute promyelocytic leukaemia (APL) that differentiates APL from other subtypes of acute myeloid leukaemia (AML). However, other subtypes of AML, without expression of CD34 and HLA-DR antigens, have also been reported.

METHODS

We analysed the HLA-DR negative de novo non-APL AML cases by dividing HLA-DR negative non-APL group into 2 sub-groups based on CD34 expression and compared the characteristics of CD34 negative HLA-DR negative with CD34 positive HLA-DR negative non-APL AML cases with respect to morphologic, immunophenotypic, molecular and clinical parameters.

RESULTS

There were 70 cases (8.54%) which were CD34 negative HLA-DR negative and 52 cases (6.34%) were CD34 positive HLA-DR negative. The median age at diagnosis was higher in CD34 negative HLA-DR negative AML than in CD34 positive HLA-DR negative AML group (38 years vs. 12 years, p < 0.001). DIC rate was higher in CD34 negative HLA-DR negative group than the other group (p < 0.001). Median total leucocyte count was higher with higher blast count in peripheral blood and bone marrow in CD34 negative HLA-DR negative AML cases than the other group (p < 0.05). CD34 negative HLA-DR negative AML was more associated with normal karyotype (96.2% vs. 38.5%; p < 0.001), NPM1 mutation (67.8% vs. 8.3%; p < 0.001) and FLT-ITD mutation (37.3% vs. 13.9%; p < 0.05). In CD34 negative HLA-DR negative group, 16 cases had co-occurrence of NPM1 and FLT3-ITD mutations, whereas no case of CD34 positive HLA-DR negative group had such dual mutation positivity. There was poor median overall survival [3.8 months (95%CI: 2.3-7.8 months) vs. 20.4 months (95% CI: 12.8-25.7 months); p = 0.0148] in CD34 positive HLA-DR negative AML than CD34 negative HLA-DR negative AML cases.

CONCLUSION

We found that the CD34 negative HLADR negative non APL AML is highly associated with NPM1 and FLT3-ITD mutation, older age at diagnosis, DIC, higher total leucocyte count, higher blast counts and normal karyotype in comparison to CD34 positive HLA-DR negative AML group. Co-occurrence of NPM1 and FLT3-ITD mutation was also exclusively seen in CD34 negative HLA-DR negative group. There was poor overall survival in CD34 positive HLA-DR negative AML than CD34 negative HLA-DR negative AML cases.

Expression levels of HLA-DR in acute myeloid leukemia: implications for antigenicity and clinical outcome

Low human leukocyte antigen (HLA)-DR expression might compromise CD4⁺ T-cell-mediated anti-tumor immunity. Its immunological and clinical significance however remain undefined in non-promyelocytic acute myeloid leukemia (AML). Taking advantage of mass spectrometry-based immunopeptidome analysis of primary AML samples (n = 31), we studied the implications of low HLA-DR expression for antigen presentation and analyzed its association with disease characteristics and survival within a cohort of 399 AML patients. Remarkably, overall HLA-DR/DQ immunopeptidome diversity was preserved in AML with low HLA-DR expression (HLA-DR^low AML) and was associated with a shift in HLA-DR/DQ allotype abundances (HLA-DQ to HLA-DR/DQ ligand ratio 0.36 vs 0.19 in HLA-DR^low and HLA-DR^high patients, respectively). Consistent with unimpaired antigenicity, survival was similar in HLA-DR^low and HLA-DR^high patients. Demonstrating for the first time that overall HLA-DR/DQ antigen presentation is preserved in HLA-DR^low AML, our findings provide a rationale for the non-inferior outcome observed in HLA-DR^low AML patients.

The diagnostic power of CD117, CD13, CD56, CD64, and MPO in rapid screening acute promyelocytic leukemia

Objective

The same immuno-phenotype between HLA-DR-negative acute myeloid leukemia (AML) and acute promyelocytic leukemia (APL) causes APL rapid screening to become difficult. This study aimed to identify the associated antigens for APL and the best model in clinical uses.

Results

A total of 36 APL (PML–RARA+) and 29 HLA-DR-negative non-APL patients enrolled in this study. When a cut-off point of 20% events was applied to define positive or negative status, APL and non-APL patients share a similar immuno-phenotype of CD117, CD34, CD11b, CD13, CD33, and MPO (P > 0.05). However, expression intensity of CD117 (P = 0.002), CD13 (P < 0.001), CD35 (P < 0.001), CD64 (P < 0.001), and MPO (P < 0.001) in APL are significantly higher while CD56 (P = 0.049) is lower than in non-APL subjects. The Bayesian Model Averaging (BMA) analysis identified CD117 (≥ 49% events), CD13 (≥ 88% events), CD56 (≤ 25% events), CD64 (≥ 42% events), and MPO (≥ 97% events) antigens as an optimal model for APL diagnosis. A combination of these factors resulted in an area under curve (AUC) value of 0.98 together with 91.7% sensitivity and 93.1% specificity, which is better than individual markers (AUC were 0.76, 0.84, 0.65, 0.82, and 0.85, respectively) (P = 0.001).

[Application of immunophenotypic analysis and molecular genetics in the diagnosis of acute promyelocytic leukemia]

Objective: To investigate the application values of immunophenotypic analysis and molecular genetics in the diagnosis of acute promyelocytic leukemia (APL) . Methods: The retrospective analyses of flow cytometric (FCM) immunophenotypic anyalysis, chromosome karyotype and chromosome fluorescence in situ hybridization (FISH) of 798 outpatient or hospitalization APL patients referred to our hospital between May 2012 and December 2017 were performed to further study the application values of FCM and molecular genetics in the diagnosis of APL. Results: The sensitivity and specificity of FCM were 91.9% and 98.7% respectively. The typical characteristic immunophenotype for APL was as of follows: a high SSC, absence of expression of cluster differntiation (CD) CD34 and HLA-DR, and expression or stronger expression of CD33, consistent expression of CD13, CD9, CD123, expression of CD56, CD7, CD2 (sometimes) . The rest 10% of the cases harbored atypical APL phenotypes, generally accompanied by CD34 and/or HLA-DR expression, decreased SSC and often accompanied by CD2 expression, it was difficult to definitively diagnose APL by this FCM phenotype, and their diagnoses depended on the results of genetics or molecular biology tests. Compared with normal individuals, complex karyotypes APL with t (15;17) translocation, other variant translocations and variant t (11;17) , t (5;17) had no significant differences in terms of their FCM phenotypes. Conclusions: FCM could rapidly and effectively diagnose APL. Despite the fact that complex karyotypes with various additional chromosomal abnormalities were detected in approximately one third of APL cases in addition to the pathognomonic t (15;17) (q22;q21) , they had no observable impact on the overall immunophenotype. Molecular and genetic criteria were the golden criteria for the diagnosis of APL. About 10% of immunophenotyping cases relied on molecular genetics for diagnosis.

[The influence of methylprednisolone on the ability of CD4⁺CD95⁺HLA-DR⁺ T-cells to produce proinflammatory medators in cultures of TCR-activated CD3⁺CD45RO⁺ T-lymphocytes from patients with rheumatoid arthritis]

The effect of different concentrations of the glucocorticoid (GC) methylprednisolone (MP) on CD4+CD95+HLA-DR+ T-cells and their ability to produce proinflammatory mediators in cultures of TCR-stimulated CD3+CD45RO+ T-lymphocytes in the in vitro system was investigated. T cells were obtained from healthy donors and patients with rheumatoid arthritis (RA).Under conditions of TCR-activation, MP increased the number of CD4+HLA-DR+CD95+ cells in CD3+CD45RO+ cultures obtained from RA patients and did not change their content in the control group. In general, MP decreased production of proinflammatory factors (IFN-, IL-2, IL-17, IL-21 and TNF-) by TCR-activated CD3+CD45RO+ cells from healthy donors and RA, consistent with the overall immunosuppressive mechanism of GC action. The correlation between CD4+CD45RO+HLA-DR+CD95+ T-cell contents and parameters reflecting production of proinflammatory mediators (IL-17, IL-21 and TNF-) in RA patients indicates maintenance of the pro-inflammatory potential of this T-cell population exposed to GC action. We suggest that relative resistance of CD4+CD45RO+CD95+HLA-DR+ T-cells of RA patients to the suppressor effect of GC leads to maintenance and even enhancement in the functional capacities of autoreactive cells in the pathogenesis of RA.

Immunophenotype distinction between acute promyelocytic leukaemia and CD15- CD34- HLA-DR- acute myeloid leukaemia with nucleophosmin mutations

Acute promyelocytic leukaemia (APL) is a unique clinicobiologic entity that can be successfully treated with All-trans Retinoic Acid ATRA-based regimens. Some cases of acute myeloid leukaemia (AML) with nucleophosmin (NPM) mutations have an immunophenotype that is similar to APL. The objective of the study is to compare antigenic expression in a group of APL patients with that in AML patients with NPM mutations and an APL-like immunophenotype (CD15- CD34- HLA-DR-). A consecutive series of 40 APL and 12 NPM patients with an APL-like phenotype were included in the study. Immunophenotypic patterns were investigated by multiparametric flow cytometry. Promyelocytic leukaemia-retinoic acid receptor-α transcript type, NPM and FLT3 mutations were investigated using conventional methods. Statistically significant differences were found between APL and NPM-mutated AML in CD33, CD13, CD2 and CD110 reactivity. CD2 expression was absent in every patient with NPM-mutated AML. In addition, mean fluorescence intensity and the coefficient of variation (cv) of CD33 and CD13 showed statistical differences between the two groups for CD33 (p = 0.007) and a trend to significance for CD13 (p = 0.05). Furthermore, among 45 evaluable patients, CD110 expression statistically differentiates between the two groups: [2/33 (6%) in the APL group and 8/12 (66.6%) in the NPM-mutated AML (p = 0.014)]. However, these traits were subtle, raising the possibility of practical diagnostic challenges. In conclusion, CD110 and CD33 reactivity may be useful to distinguish APL from NPM-mutated AML with CD15, CD34 and HLA-DR negativity. Nevertheless, cytogenetic and molecular characterization is necessary to establish the accurate diagnosis of AML.

Flow cytometry rapidly identifies all acute promyelocytic leukemias with high specificity independent of underlying cytogenetic abnormalities

Acute promyelocytic leukemia (APL) is a highly aggressive disease requiring prompt diagnosis and specific early intervention. Immunophenotyping by flow cytometry (FCM) facilitates a rapid diagnosis, but commonly used criteria are neither sufficiently sensitive nor specific. With an antibody panel for diagnostic screening in routine practice, we found all 149 APL cases in this study exhibited a unique immunophenotypic profile, ie, a characteristic CD11b- myeloid population and absent CD11c expression in all myeloid populations; 96.6% of cases also lacked HLA-DR expression. These distinctive features allowed recognition of all unusual cases phenotypically resembling the regular myeloblasts (CD34+/HLA-DR+) or granulocytes (CD117-/CD34-/HLA-DR-). FCM effectively identified all 19 APL cases with variant translocations, including cases with a normal karyotype due to a cryptic submicroscopic t(15;17)(q22;q21), t(11;17)(q23;q21) that escaped the detection by fluorescence in situ hybridization for t(15;17) and der(15)ider(17)(q10) that lacked a simple reciprocal t(15;17). When APL-associated profiles were validated against 107 AML cases of non-APL subtypes, including 51 HLA-DR- cases, the diagnostic specificity and positive predictive value were 98%. FCM effectively provides independent detection of APL during diagnostic workup and harmonizes with the subsequent molecular cytogenetic diagnosis.

HLA-DRneg patients without acute promyelocytic leukemia show distinct immunophenotypic, genetic, molecular, and cytomorphologic characteristics compared to acute promyelocytic leukemia

BACKGROUND

Loss of HLA-DR and CD34 is a well-known characteristic of malignant promyelocytes in acute promyelocytic leukemia (APL). However, this immunophenotype is not specific for APL. The purpose of this study was to investigate whether further biological characterization of the HLA-DR(neg) acute myeloid leukemia patients would allow more clearly define criteria to separate APL from non-APL patients.

METHODS

Immunophenotyping, cytogenetics, molecular analyses, and cytomorphology were prospectively performed within routine leukemia diagnostics of 800 patients included in different prospective acute myeloid leukemia multicenter trials.

RESULTS

Beside 60 APL, an additional 62 HLA-DR(neg) non-APL patients were identified. The main differential characteristics of HLA-DR(neg) non-APL included high CXCR-4 expression in most patients and almost all leukemia cells, a significantly higher proportion of patients presenting with NPM1 mutations as well as the significant association with cup-like nuclear morphology. The biological distinctness of both leukemia subtypes was further emphasized by the complete absence of aberrant CD2 expression and increased leukocyte and platelet counts in HLA-DR(neg) non-APL patients. Even in the CD34(pos) subgroup of HLA-DR(neg) non-APL all those features contributed in at least the same way to the separation from APL.

CONCLUSIONS

The results of the present study show that an immunophenotypic, molecular, and cytomorphologic separation of both HLA-DR(neg) leukemia subgroups is possible indicating that both groups are biologically distinct.

Immunophenotypic profile of acute leukemia: critical analysis and insights gained at a tertiary care center in India

BACKGROUND

To analyze the spectrum of various types and subtypes of acute leukemia.

METHODS

Two thousand five hundred and eleven consecutive new referral cases of acute leukemia (AL) were evaluated based on WHO classification.

RESULTS

It included 1,471 cases (58%) of acute lymphoblastic leukemia (ALL), 964 cases (38%) of acute myeloid leukemia (AML), 45 cases (1.8%) of chronic myelogenous leukemia in blast crisis (CMLBC), 37 cases (1.5%) of biphenotypic acute leukemia (BAL), 1 case of Triphenotypic AL, and 2 cases of acute undifferentiated leukemia (AUL). Common subtypes of ALL were B-cell ALL (76%), which comprised of intermediate stage/CALLA positive (73%), early precursor/proBALL (3%). T-cell ALL constituted 24% (351 cases) of ALL. Common subtypes of AML included AMLM2 (27%), AMLM5 (15%), AMLM0 (12%), AMLM1 (12%), APML (11%), and AML t(8;21) (9%). CMLBC was commonly of myeloid blast crisis subtype (40 cases).

CONCLUSION

B-cell ALL was the commonest subtype in children and AML in adults. Overall incidence of AML in adults was low (53% only). CD13 was most sensitive and CD117 most specific for determining myeloid lineage. A minimal primary panel of nine antibodies consisting of three myeloid markers (CD13, CD33, and CD117), B-cell lymphoid marker (CD19), T-cell marker (CD7), with CD45, CD10, CD34, and HLADR could assign lineage to 92% of AL. Cytogenetics findings lead to a change in the diagnostic subtype of myeloid malignancy in 38 (1.5%) cases.