The Immature Platelet Fraction Is Sensitive to the Platelet Size and a Useful Parameter for Screening for Macrothrombocytopenia

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 1097-1097
Author(s):  
Koji Miyazaki ◽  
Yukako Koike ◽  
Mikio Danbara ◽  
Ryouichi Horie ◽  
Masaaki Higashihara
Keyword(s):  
Cold Storage ◽  
Conflicts Of Interest ◽  
Large Cell ◽  
Dependent Manner ◽  
Invasive Treatment ◽  
Distribution Width ◽  
Reticulated Platelets ◽  
Platelet Size ◽  
Immature Platelet Fraction ◽  
Platelet Aggregates

Abstract Abstract 1097 The immature platelet fraction (IPF) is a useful parameter indicating thrombopoietic activity to differentiate the causes of thrombocytopenia. We previously reported that the percentage of IPF (%IPF) is negatively correlated to the platelet count among ITP patients, and not among myelodysplastic syndrome (MDS) patients. We also noticed that some MDS patients exhibited extremely high %IPF values, which were dissociated from the percentages of reticulated platelets (%RP) measured by flow cytometry. Such discrepancies were also observed in hereditary macrothrombocytopenias, which are sometimes difficult to be distinguished from ITP, because ITP also exhibits increased number of reticulated platelets in a slightly larger size. Once misdiagnosed, a hereditary macrothrombocytopenia patient might be subjected to an invasive treatment such as splenectomy. In order to avoid such mistreatments, a clear marker to differentiate macrothrombocytopenia is desperately needed. In this study, we investigated the IPF values of 16 individuals from 12 families with various hereditary macrothrombocytopenia in order to clarify whether the IPF could be a useful marker to distinguish macrothrombocytopenia from ITP, and examined the IPF during EDTA aggregation and cold-storage to elucidate how platelet size may affect the IPF value. The IPF values were about 5 times higher in MYH9 disorders (%IPF 48.0 ± 1.8) and about 1.5 times higher in other macrothrombocytopenias (%IPF 17.0 ± 2.2) than immune thrombocytopenic patients with similar platelet counts (%IPF 9.3 ± 0.4). These results suggested that the platelet size can affect the IPF value. However it still remains the possibility that some factors specific to these macrothrombocytopenias other than the platelet size might make an influence on the IPF, because the characteristic of large platelets in hereditary macrothrombocytopenia has not been fully understood, and no one knows whether large platelets are functionally identical to normal platelets except for the size. In order to exclude the possibility, we next examined the changes of IPF values during EDTA aggregation and cold-storage. The IPF was significantly increased during storage in a time dependent manner along with forming platelet clumps. The IPF was strongly influenced by a few tiny platelet aggregates rather than other platelet indices, such as mean platelet volume (MPV), platelet-large cell ratio (P-LCR) and platelet distribution width (PDW). In conclusion, the IPF is susceptible to the platelet size, and could be a useful parameter for screening of macrothrombocytopenia from ITP. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Evaluation of an Alternative Staining Method Using SYTO 13 to Determine Reticulated Platelets

2019 ◽  
Vol 119 (05) ◽  
pp. 779-785 ◽  
Author(s):  
Laura Hille ◽  
Marco Cederqvist ◽  
Julia Hromek ◽  
Christian Stratz ◽  
Dietmar Trenk ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Reactivity ◽  
Dependent Manner ◽  
Reticulated Platelets ◽  
Automated Assay ◽  
Rna Quantification ◽  
Time Period ◽  
Immature Platelet Fraction ◽  
Syto 13

AbstractReticulated platelets reflect the rate of platelet turnover and represent the youngest circulating platelets in peripheral blood. Reticulated platelets contain residual ribonucleic acid (RNA) from megakaryocytes which is lost in a time-dependent manner and can be transcribed into proteins even in the absence of a nucleus. An increased proportion of reticulated platelets is associated with higher platelet reactivity, cardiovascular events and mortality. At present, a fully automated assay system (SYSMEX haematology analyser) is available for analysis. This method, however, is not suitable for extended laboratory investigations like subsequent cell sorting. Flow cytometry analysis after staining with thiazole orange (TO) is frequently used in such settings despite several limitations. Here, we describe a new assay for determination of reticulated platelets by flow cytometry using the nucleic acid staining dye SYTO 13 and compare it with SYSMEX and TO staining as current standards. A significant correlation between immature platelet fraction (IPF) determined by SYSMEX XE-2100 analyser and results obtained with the SYTO 13-based assay was observed (r = 0.668, p < 0.001) which was stable during a reasonable time period. In contrast, the correlation between TO staining and IPF was weaker (r = 0.478, p = 0.029) and lost after 90 minutes of staining. SYTO 13 staining of platelets enabled sorting of RNAlow and RNArich platelets which was confirmed by RNA quantification of sorted platelets. Except for fixation of platelets, sorting of these platelet sub-populations was stable under various experimental settings. In summary, determination of reticulated platelets with the new SYTO 13 assay offers distinct technical advantages enabling further laboratory processing.

Immature Platelet Fraction in Different Diagnosis of Thrombocytopenic States: An Approach to Distinguish Idiopathic Thrombocytopenic Purpura from Myelodysplastic Syndrome with Isolated Thrombocytopenia.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1085-1085
Author(s):  
Koji Miyazaki ◽  
Miyako Taira ◽  
Tomiteru Togano ◽  
Manabu Ohsaka ◽  
Yuhko Suzuki ◽  
...  
Keyword(s):  
Blood Transfusion ◽  
Myelodysplastic Syndrome ◽  
Idiopathic Thrombocytopenic Purpura ◽  
Inverse Correlation ◽  
Consensus Method ◽  
Thrombocytopenic Purpura ◽  
Distribution Width ◽  
Platelet Counts ◽  
Reticulated Platelets ◽  
Immature Platelet Fraction

Abstract It is sometimes confusing to distinguish idiopathic thrombocytopenic purpura (ITP) from thrombocytopenia due to dysmegakaryopoiesis, as seen in myelodysplastic syndrome (MDS) patients, especially MDS with isolated thrombocytopenia. In this study, we investigated the useful parameters for the different diagnosis of thrombocytopenia. The number of reticulated platelets reflects the rate of thrombopoiesis, and this clinical utility has been established in the laboratory diagnosis of thrombocytopenia due to increased peripheral platelet destruction, such as autoimmune thrombocytopenic purpura (AITP). However, the number of reticulated platelets has not been well investigated in the patients with myelodysplatsic syndrome (MDS), while some of them are misdiagnosed as ITP. The aim of this study is to evaluate the diagnostic utility of the measurements of reticulated platelets as well as other parameters of platelets, such as MPV (mean platelet volume), P-LCR (platelet larger cell ratio) and PDW (platelet distribution width). The reticulated platelets, expressed as the immature platelet fraction (IPF) were determined in 108 ITP and 57 MDS patients using the Sysmex XE-2100 blood cell counter with upgraded software (Sysmex, Kobe, Japan). This system enabled rapid, inexpensive, automated, stable measurements of reticulated platelets compared with the flow cytometry system, of which consensus method has not yet been identified to provide acceptable intra- and inter-laboratory results. The platelet counts in ITP and MDS patients were equivalent (ITP, 7.99 ± 0.40 × 104/μL; MDS, 8.05 ± 0.57× 104/μL). The IPF values in ITP patients (10.4 ± 0.61%) were significantly higher than those in MDS (5.82 ± 0.63%), and the inverse correlation between the IPF and the platelet counts was observed among the ITP patients, but not among the MDS. Both MPV and PDW in MDS (10.6 +/− 0.15 fL and 12.2+/−0.41 fL, respectively) were significantly higher than in ITP (7.7 +/− 0.38 fL and 9.4 +/− 0.48 fL, respectively), while P-LCR in MDS (28.7 +/− 1.2%) and ITP (23.6 +/− 1.3%) were not significantly different. Although MPV was correlated with IPF among either group, the correlation between IPF and either PDW or P-LCR was weak among MDS (IPF × PDW, r=0.673; IPF × P-LCR, r=0.660) compared with ITP (IPF × PDW, r=0.779; IPF × P-LCR, r=0.803). Next we precisely investigated the clinical features of the minor population of MDS with higher IPF. Most of these patients revealed the significantly higher values of PAIgG (Platelet-associated IgG) and/or poor response to the blood transfusion, suggesting the possibility of associated autoimmune mechanisms. The patients of MDS in overt leukemic stage also recorded higher IPF even if they had no or few blood transfusion. The IPF would be a useful parameter to distinguish ITP from MDS with isolated thrombocytopenia, which has been shown to have a favorable prognosis.

The Routine Measurement of Platelet Size Using Sodium Citrate Alone as the Anticoagulant

1993 ◽  
Vol 70 (04) ◽  
pp. 687-690 ◽  
Author(s):  
P M W Bath
Keyword(s):  
Incubation Time ◽  
Sodium Citrate ◽  
Dependent Manner ◽  
High Concentration ◽  
Distribution Width ◽  
Routine Measurement ◽  
Platelet Size ◽  
Coefficients Of Variation ◽  
Important Marker ◽  
Made In

SummaryMean platelet volume (MPV), a measure of platelet size, is becoming recognised as an important marker of platelet function. However, platelets swell in edetic acid (EDTA), the Standard haematology anticoagulant, in a time-dependent manner making such measurements potentially unreliable. The effect of incubation time on MPV, and platelet distribution width (PDW), as measured in EDTA, low (1:9 volume/volume with blood) or high (1:4 v/v with blood) concentration sodium citrate was studied. MPV measured in high concentration sodium citrate did not change with time in contrast to MPV measured in either low concentration sodium citrate or EDTA which both increased in an inverse exponential fashion. MPV and PDW, measured in high concentration sodium citrate, had similar within-assay and between-assay coefficients of Variation as other platelet, red cell and white cell haematology variables measured in EDTA: MPV 1.4%, 2.1%; PDW 1.4%, 1.5%; MCV 0.4%, 0.7%; PC 3.1%, 6.1%; WCC 1.5%, 7.3%; Hb 2.1%, 2.4% respectively. MPV measured in EDTA and corrected for incubation time approximated to, but was higher than, the MPV measured in high concentration sodium citrate. PDW correlated inversely with platelet count (r = <0.415, 2p <0.001). MPV may be measured in sodium citrate (at 1:4 v/v with blood) alone with a better accuracy and reproducibility than similar measurements made in EDTA. Furthermore, such measurements are not influenced by incubation time, unlike for EDTA.

scholarly journals Platelet size as a predictor for severity and mortality in COVID-19 patients: a systematic review and meta-analysis

2021 ◽  
Author(s):  
Sarah A Daniels ◽  
Hua Wei ◽  
David W Denning
Keyword(s):  
Systematic Review ◽  
Hospital Admission ◽  
Meta Analysis ◽  
Large Cell ◽  
Platelet Activity ◽  
Distribution Width ◽  
Platelet Size ◽  
Standard Mean Difference ◽  
Increased Risk ◽  
Quality Rating

Background: Parameters reflecting platelet size can be sensitive indicators that circulating platelets are activated and COVID-19 patients are at increased risk of thrombosis. This systematic review aims to assess the association of mean platelet volume (MPV), platelet distribution width (PDW) and platelet-large cell ratio (P-LCR) with disease severity and mortality in COVID-19 patients. Methods: English and Chinese databases were searched electronically to identify studies reporting data on MPV, PDW or P-LCR in COVID-19 patients. Included articles underwent a quality rating. A meta-analysis was performed using the standard mean difference and interpreted as the common language effect size (CLES). Results: Twenty-two studies (11,906 patients) were included in the meta-analysis. Of these, 14 were rated poor and eight were fair. The MPV and P-LCR was significantly higher at hospital admission in severe patients compared to non-severe patients. The MPV, PDW and P-LCR were significantly higher at hospital admission in non-survivors compared to survivors. There was a marked increase in the probability of a severe COVID-19 patient presenting with higher P-LCR at hospital admission than a non-severe patient (CLES: 68.7% [95% CI: 59.8%, 76.5%]), when compared with MPV and PDW ((CLES: 59.2% [95% CI: 53.1%, 65.1%]) and (CLES: 55.9% [95% CI: 50.6%, 62.2%]), respectively). Conclusion: Severe COVID-19 disease is associated with the increased production of larger, younger platelets. When comparing MPV, PDW and P-LCR, P-LCR is the most important biomarker for evaluating platelet activity. P-LCR testing at hospital admission could identify COVID-19 patients with increased risk for thrombotic events, allowing preventative treatment.

Immature Platelet Fraction As a Measure of Thrombocytopenia in Trauma Patients and Its Cut off Value with Severity of Thrombocytopenia

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4681-4681
Author(s):  
Bhaumik Arvindkumar Shah ◽  
Arulselvi Subramanium ◽  
Hara prasad Pati ◽  
Subhadra Sharma ◽  
Deepak Agrawal ◽  
...  
Keyword(s):  
Platelet Count ◽  
Sofa Score ◽  
Injury Severity ◽  
Conflicts Of Interest ◽  
Statistical Significance ◽  
Common Finding ◽  
Trauma Patients ◽  
Reticulated Platelets ◽  
Immature Platelet Fraction ◽  
Significant Difference

Abstract Abstract 4681 Thrombocytopenia is common finding in trauma patients. However, platelet count fluctuates widely. Therefore, Immature Platelet Fraction is being studied for whether it can complement the platelet count. Immature platelet fraction (IPF ) is a measure of reticulated platelets (RPs), which represents the state of thrombopoiesis. IPF is obtained from an automated haematology analyzer. It is proportional to reticulated platelets and expressed as percentage of Total optical count. Aim To establish cut off value of IPF (%) with increasing severity of thrombocytopenia in trauma patients which can be useful for diagnosis and monitoring of the cases. Material and methods Total 69 patients admitted in J.P.N Apex trauma centre (AIIMS) were studied within first 24 hrs after injury. Peripheral blood was collected in K2EDTA tube for measurement of platelet count using a fully automated analyzer Sysmex XE 2100 (Japan). RET channel was selected for the measurement of IPF%.The patients were categorized with platelet count between 150×103/μ l and 100×103/μ l, between 100×103/μ l and 50×103/μ l, and below 50×103/μ l. Immature platelet fraction was measured in all categories of thrombocytopenia and statistically compared. Each patient was ascribed New Injury Severity Score and SOFA (sequential organ failure assessment) score and their correlation with IPF value was assessed. ROC curve was used to establish cut off value of IPF between those with platelet count above150×103/μ l and below 150×103/μ l and between those with platelet count above 100×103/μ l and below 100×103/μ l. Results Using Mann Whitney test, the patients (n=41) with platelet count < 150×103/μ l showed mean IPF (%) (18.19 ± 9.43, range: 4.0 – 46.6) which was significantly higher (p<0.0001) than that of subjects (n=28) with platelet count above 150×103/μ l,in which mean IPF (%) value was (8.94 ± 5.79, range:2.3 − 24.9). The cut–off value of IPF > 12.5% was found in patients having platelet count < 150×103/μ l. Similarly, the patients (n=22) with platelet count < 100×103/μ l showed mean IPF (%) (22.04 ± 9.94, range:10.8-46.6) which was significantly higher (p<0.0001) than that of patients (n=47) with platelet count above 100×103/μ l in which mean IPF (%) value was (10.87 ± 6.51, range:2.3 − 35.4). The cut–off value of IPF > 14.95 % was found in patients having platelet count <100×103/μ l. Using Kruskal-Wallis test, IPF (%) value (23.31 ± 10.44, range: 11.2 – 46.6) in patients (n=18) with platelet count between (50×103/μ l – 100×103/μ l) was found to be significantly higher (p=0.003) than the value (13.73 ± 6.58, range: 4 – 35.4) obtained in patients (n=19 ) with platelet count between (100×103/μ l – 150×103/μ l). No statistical significance was found between IPF (%) value (13.73 ± 6.58, range: 4 – 35.4) obtained in patients (n=19) with platelet counts between (100×103/μ l – 150×103/μ l) and IPF(%) value (16.3 ± 4.41, range:10.8-20.3) in patients (n=4) with platelet count below 50×103/μ l. Similar result was obtained between IPF(%) value (23.31 ± 10.44, range:11.2-46.6) in patients (n=18) with platelet count between (50×103/μ l – 100×103/μ l) and IPF(%)value (16.3 ± 4.41,range:10.8-20.3) in patients (n=4) with platelet count below 50×103/μ l. IPF value (19.64 ± 7.88, range:6.6 − 35.4) was found to be significantly higher (p<0.0001) in patients (n=19) with SOFA score ≥8 as compared to the patients with SOFA score <8,which showed IPF (%) value (12.46±9.10, range:2.3-46.6). In contrast, no significant difference in IPF value was found in the context of New ISS score. Conclusion: Immature platelet fraction could be a reasonable and reliable measure of thrombocytopenia which can be used to diagnose and monitor the severity of thrombocytopenia in trauma patients. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Hematological Findings in Non-Treated and γ-Irradiated Mice Deficient for MIC-1/GDF15

2018 ◽  
pp. 623-636
Author(s):  
M. HOFER ◽  
Z. HOFEROVÁ ◽  
J. REMŠÍK ◽  
M. NOVÁKOVÁ ◽  
J. PROCHÁZKOVÁ ◽  
...  
Keyword(s):  
Progenitor Cells ◽  
Hematological Parameters ◽  
Blood Platelet ◽  
Dependent Manner ◽  
Distribution Width ◽  
Knock Out ◽  
Pathological Conditions ◽  
Platelet Size ◽  
Radiation Induced

Several members of the TGF-ß family are known to effectively regulate the fate of hematopoietic progenitor cells in a complex and context-dependent manner. Growth differentiation factor-15 (GDF15) is a divergent member of the TGF-ß family. This stress-induced cytokine has been proposed to possess immunomodulatory functions and its high expression is often associated with progression of a variety of pathological conditions. GDF15 is also induced by chemotherapy and irradiation. Very few fundamental studies have been published regarding the effect of GDF15 in hematopoiesis. In this study, we analyzed the hematological status of untreated and γ-irradiated mice deficient for GDF15 as a result of genetic knock-out (KO), in order to clarify the regulatory role of GDF15 in hematopoiesis. Significant differences between GDF15 KO mice and their pertinent WT controls were found in the parameters of blood monocyte numbers, blood platelet size, and distribution width, as well as in the values of bone marrow granulocyte/macrophage progenitor cells. Different tendencies of some hematological parameters in the GDF15 KO mice in normal conditions and those under exposure of the mice to ionizing radiation were registered. These findings are discussed in the context of the GDF15 gene function and its lack under conditions of radiation-induced damage.

scholarly journals Immature platelet fraction: is a novel early predictive marker for disease severity in patients with Covid-19 pneumonia?

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Said Incir ◽  
Zeynep Komesli ◽  
Arzu Baygul ◽  
Zeynep Atam Tasdemir ◽  
Kerim Erhan Palaoglu ◽  
...  
Keyword(s):  
Independent Predictor ◽  
Oxygen Demand ◽  
Predictive Marker ◽  
Large Cell ◽  
Operating Characteristics ◽  
Platelet Volume ◽  
Distribution Width ◽  
Immature Platelet Fraction ◽  
Severe Group ◽  
Risk Patients

Abstract Objectives In many diseases, immature platelet fraction (IPF%) is related to coagulopathy and poor outcome. This study aimed to investigate the predictive value of IPF% for the severity of pneumonia in patients with Coronavirus Disease 2019 (COVID-19). Methods A total of 154 patients with COVID‐19 infections were included. The patients were divided into two groups according to the severity of pneumonia (severe and non-severe) regarding their oxygen demand. Results Given laboratory parameters, the median IPF% was significantly higher in the severe group (11.9 vs. 3.9%, p<0.001). Mean platelet volume (p<0.001), platelet-large cell ratio (p=0.001), platelet distribution width (p=0.001), D-Dimer (p<0.001), INR (p=0.003), and aPTT (p=0.007) were also found to be significantly higher in the severe group. Moreover, IPF (p=0.014, Odds ratio = 2.000, 95%CI: 1.149-3.482) was an independent predictor for the severity. The curve value from receiver operating characteristics was 0.879 (p<0.001, 95%CI: 0.784-0.943) for determining the severity of pneumonia. IPF% had a sensitivity and specificity value of 69.5 and 92.4% to detect the disease’s severity. Conclusions IPF% is an independent predictor for the severity of COVID-19 pneumonia. Assessment of IPF% may both help to early determine high-risk patients with COVID-19 and to alert the physicians.

Immature platelet fraction measurement is influenced by platelet size and is a useful parameter for discrimination of macrothrombocytopenia

Hematology ◽  
2015 ◽  
Vol 20 (10) ◽  
pp. 587-592 ◽  
Author(s):  
Koji Miyazaki ◽  
Yukako Koike ◽  
Shinji Kunishima ◽  
Ryuji Ishii ◽  
Mikio Danbara ◽  
...  
Keyword(s):  
Platelet Size ◽  
Immature Platelet Fraction ◽  
Fraction Measurement

scholarly journals Cytokine-Mediated Natural Killer Cells Effects Impair Hematopoietic Stem Cell Function

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2641-2641
Author(s):  
Lorena Lobo Figueiredo-Pontes ◽  
Robert S. Welner ◽  
Miroslava Kardosova ◽  
Hong Zhang ◽  
Meritxell Alberich-Jorda ◽  
...  
Keyword(s):  
Stem Cell ◽  
Nk Cells ◽  
Natural Killer ◽  
Cytokine Production ◽  
Cell Function ◽  
Conflicts Of Interest ◽  
Cytokine Signaling ◽  
Dependent Manner ◽  
Hematopoietic Stem ◽  
Nk Cytotoxicity

Abstract Natural killer (NK) cells participate in innate and adaptive immune responses, and upon activation rapidly produce cytokines, chemokines, and growth factors, including IFNγ, TNFα, TGFβ, GM-CSF, MIP1α, MIP1β, IL-10, and others, which can affect the function of other hematopoietic cells. Considering the recent evidences that hematopoietic stem cells (HSCs) respond to cytokine signaling, we hypothesized that NK cell-mediated cytokine production could mediate HSC function. By the use of co-cultures of purified Ly5.1 murine NK cells and congenic Ly5.2 HSCs, we concluded that NK activity affects HSC frequency in vitro as well as hematopoietic reconstitution in vivo. Sorted NK cells (CD3- NK1.1+) and HSCs (Lin-, Sca1+, ckithi, CD48-, CD150+) were co-cultured in the presence or absence of IL2 over an OP9 stromal cells layer for 14 to 28 days. After 14 days, the addition of NK cells to HSC cultures resulted in an approximate 2-fold reduction of lineage negative cells (Lin-) recovered cells, as compared to control HSC cultures, as determined by flow cytometry analysis. Lin- counts were even lower in HSC+NK long-term cultures when compared to HSC only cultures. Ly5.1 HSCs and/or Ly5.2 NK cells were injected into sublethally irradiated Ly5.1/2 chimeric mice in a ratio of 105 NK to 103 HSCs per mouse. The addition of IL2-stimulated NK to injected HSCs reduced engraftment from 15.7% to 1.82% when the 16 weeks bone marrow (BM) chimerism was analyzed. In agreement, donor CD45.1 cells contribution to the LSK and HSC subpopulations was reduced in the HSC+NK transplanted mice. To test whether NK depletion from BM grafts would affect HSC function, we performed limiting dilution transplantation assays where whole BM from Ly5.2 mice was submitted to immunonagnetic NK1.1 or IgG depletion and injected into lethally irradiated Ly5.1 animals. Donor chimerism after 8 and 16 weeks of transplant showed that depleting NK cells improves the engraftment ability of HSC in a cell dose-dependent manner. When 25 x104 BM cells were injected, chimerism increased from 40 to more than 90% in NK depleted group. Of note, HSC frequency was 1 in 1595 in the control and 1 in 95 in the NK depleted group. In order to understand the mechanisms by which NK cells could regulate HSCs, we took advantage of a CCAAT/enhancer-binding protein gamma (C/ebpg) knockout (KO) conditional mouse model generated in our laboratory, considering that C/ebpg had been previously shown to regulate NK cytotoxicity. Using similar culture conditions, HSCs and NK cells isolated from control (CT) or Cebpg KO mice were injected into congenic sublethally irradiated recipients. Results showed that Cebpg-deficient NK cells do not harm HSC engraftment as CT NK cells do. For instance, after 8 weeks, the addition of CT non-stimulated and IL-2-stimulated NK cells to normal transplanted HSCs reduced the engraftment from 40% to 20% and 10%, respectively. In contrast, chimerism was not different when HSCs only or HSCs + stimulated KO NK cells were transplanted. Gene expression and cytokine profiles of deficient and normal NK cells revealed the potential players of this HSC-NK regulation. Of these, interferon gamma (IFNg), was lower produced by the C/ebpg deficient NK cells. Therefore, besides controlling NK cytotoxicity, we showed here that C/ebpg also plays a role in the regulation of HSCs by NK-mediated cytokine production. Next, we investigated whether depletion of NK cells from human BM samples would improve transplantation efficiency. NK cells were removed using CD56 antibody and transplanted into sublethally irradiated NSG mice. Sixteen weeks after transplantation, animals were sacrificed and the percentage of human CD45 cells in blood, BM, and spleen demonstrated that NK depletion from human BM favors engraftment. Altogether, these findings provide new insights to the knowledge of HSC regulation by NK cells, which are present in BM transplantation (BMT) grafts. Although the alloreactive effect of NK cells against non-identical tumor cells from BMT recipients is well known, its cytokine-mediated effects over identical progenitor cells from the graft were not previously explored. We show that NK-secreted cytokines harm stem cell function, thus suggesting that depletion of NK cells from BM donor cells preparations can improve stem cell engraftment, particularly in the setting of alternative transplants with limiting cell numbers or non-myeloablative conditioning regimens. Disclosures No relevant conflicts of interest to declare.

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