Barriers and facilitators to cord blood banking among pregnant women at a university obstetric clinic.

BACKGROUND: Cord blood (CB) is a cell source for hematopoietic stem cell transplantation. In 2019, the percentage of births with CB collected for banking was only 3% nationally and 0.05% in our state. To increase CB donations, we need to understand pregnant women's awareness and knowledge of, plus barriers and facilitators to, CB banking (CBB). STUDY DESIGN AND METHODS: We recruited 289 women in their third trimester from an academic obstetric clinic between October 2020 and May 2021. Women attending this clinic come from all parts of the state in addition to local city residents. After agreeing to participate, participants completed a survey using Research Electronic Data Capture (REDCap). Data were analyzed using SAS version 9.4. RESULTS: Exactly 58.9% of participants had heard of CBB, but only 26.53% understood its purpose; 10.03% indicated someone had discussed CBB with them, and 61.3% were undecided about it. The preferred source of information was the clinic provider (82.1%), followed by CB bank staff (36.8%). The requested mode for receiving information was face-to-face with their provider, including written materials. Income, education, and marital status did not have a significant influence on information preferences. DISCUSSION: Lack of knowledge continues to be a major barrier to CBB. Developing educational interventions based on womens' preferences may increase understanding of CBB. Study participants preferred that the healthcare provider deliver this information. This study was done in a primarily rural, southern state, while previous studies were in larger metropolitan areas, yet results are comparable.

A hands-on resident umbilical cord blood educational curriculum compared to online education of post-residency obstetricians: comparison of the volume of collected cord blood units.

BACKGROUND: Umbilical cord blood unit (CBU) volume is a predictor of its later clinical utility. Many studies suggest the need to increase the volume of CBU collected, but most obstetrical providers receive no formal collection training. STUDY DESIGN AND METHODS: We designed and implemented an educational curriculum for obstetrics residents aimed at improving collection methods and increasing CBU volumes (CBUV). Residents were required to attend grand rounds and interactive didactic sessions on CBU collection followed by work with a simulated collection kit and then performed training collections under observation by a trained collector. Residents completed a self-assessment after each collection and received immediate personal feedback. Outside providers (non-UAMS physicians) received written instructional materials with the collection kits and had access to online training materials. They received feedback regarding their collection via standard mail. CBU donated to Cord Blood Bank of Arkansas for public use from 2014-2016 were analyzed. CBUV from residents were compared to those from outside providers. RESULTS: After adjusting for maternal age and race, infant gender, gestational age, and birth weight, the least-squared mean CBUV was 92.1 mL for UAMS collections and 65.5 mL for outside provider collections. The improved CBUV of UAMS providers is statistically significant (p < 0.0001). CONCLUSION: Our educational intervention was successful, and we believe that it can be replicated in other obstetrical residency programs. Cord blood collection education involving hands-on training with a model and immediate feedback improves CBUV, decreases kit waste, increases likelihood of CBU storage, and, therefore, inventory for transplantation.

Optia® continuous mononuclear collection (CMNC) system is a safe and efficient system for hematopoietic progenitor cells-apheresis (HPC-a) collection and yields a lower product hematocrit (HCT%) than the COBE® spectra system: A retrospective study.

PURPOSE: We evaluated the Optia® continuous mononuclear collection (CMNC) system for hematopoietic progenitor cell-apheresis (HPC-A) collection (Terumo BCT, Lakewood, CO) compared to the COBE® Spectra (Terumo BCT, Lakewood, CO), including both large volume leukapheresis (LVL) and non-LVL collections. METHODS: We performed a retrospective data analysis of all autologous HPC-A collections with the Optia® CMNC system (n = 93; LVL = 59, non-LVL = 34) since implementation at our institution and compared it with a similar number of concurrent collections utilizing the COBE® Spectra (n = 96; LVL = 68, non-LVL = 28). The population studied included multiple myeloma (62 patients/171 collections) and lymphoma (5 patients/18 collections). Mobilization was achieved using chemotherapy + G-CSF (n = 108), chemotherapy + G-CSF + plerixafor (n = 67), G-CSF alone (n = 10), or G-CSF + plerixafor (n = 4). Based on our minimum predicted collection formula and the collection goal, 7-30 L of whole blood was processed. Per protocol, a minimum of 2 days of collection was performed. RESULTS: HPC-A collected on Optia® CMNC had lower %HCT than those collected on COBE® Spectra (3.7 versus 4.3%, P = .029). There were no statistically significant differences between the two devices for other variables examined, including preapheresis WBC count and CD34+ cell count, procedure time, whole blood volume processed, collection efficiency (CE2), % platelet loss and throughput. CE2 for both devices was higher when <30 L of whole blood volume was processed. A linear correlation was noted between the preapheresis CD34+ cell count and CD34+ cells collected. No adverse events or bleeding episodes were noted, even when acetyl salicyclic acid (ASA) was given. CONCLUSIONS: Optia® CMNC system is equivalent to the COBE® Spectra, with significantly lower product HCT%.

Risk factors for MDS and acute leukemia following total therapy 2 and 3 for multiple myeloma.

Lenalidomide has been linked to myelodysplastic syndrome (MDS) after autotransplants for myeloma. Total therapy trials (TT; TT2(-/+) thalidomide) and TT3 (TT3a with bortezomib, thalidomide; TT3b with additional lenalidomide) offered the opportunity to examine the contribution of these immune-modulatory agents to MDS-associated cytogenetic abnormalities (MDS-CA) and clinical MDS or acute leukemia ("clinical MDS/AL"). Of 1080 patients with serial cytogenetic studies, MDS-CA occurred in 11% and clinical MDS/AL in 3%. Risk features of MDS-CA included TT3b, age ≥65 years, male gender, levels of ß-2-microglobulin >5.5 mg/L, and multiple myeloma relapse. Clinical MDS/AL occurred less frequently in the control arm of TT2 and more often with TT3a and TT3b. Since MDS-CA often antedated clinical disease, periodic cytogenetic monitoring is recommended. Larger CD34 quantities should be collected upfront as the risk of MDS could be reduced by applying higher CD34 doses with transplant. Thus, treatment, host, and myeloma features could be linked to MDS development after therapy for this malignancy. This trial was registered at www.clinicaltrials.gov: TT3A: NCT00081939, TT3B: NCT00572169.

Rituximab and intermediate-purity plasma-derived factor VIII concentrate (Koate®) as adjuncts to therapeutic plasma exchange for thrombotic thrombocytopenic purpura in patients with an ADAMTS13 inhibitor.

Thrombotic thrombocytopenic purpura (TTP) results from a congenital or acquired deficiency of the von Willebrand factor (vWF)-cleaving protease ADAMTS13. The disease can be fatal and hence treatment should be initiated promptly. Therapeutic plasma exchange (TPE) remains the standard treatment along with adjunct therapies including steroids and immunosuppressive drugs. Addition of rituximab to TPE has been shown to be beneficial in refractory/relapsing TTP; however, TPE results in removal of rituximab from the circulation requiring more frequent dosing of rituximab to achieve a favorable outcome. The intermediate-purity plasma-derived Factor VIII concentrate (FVIII) Koate® contains the highest amount of ADAMTS13 activity yet reported and has been used successfully in treating congenital TTP. Here we report our experience with addition of this FVIII concentrate to rituximab, corticosteroids and TPE in three TTP patients with an ADAMTS13 inhibitor to permit withholding TPE for 48 h after rituximab infusion.

Analysis of CD34+ cell collection using two mobilization regimens for newly diagnosed multiple myeloma patients reveals the separate impact of mobilization and collection variables.

Mobilization regimens for CD34+ cells have generally been judged successful based on the number of cells collected without evaluating mobilization separately from collection. Using retrospective data for patients who collected CD34+ cells on Total Therapy protocols 3a/3b (VTD-PACE) and Total Therapy 4/5 using a novel regimen that added low dose melphalan to VTD-PACE (MVTD-PACE), we analyzed mobilization and collection variables separately. A significant difference favoring MVDT-PACE was found in mean CD34+ cells/µL on day 2 of collection and in mean ratio of CD34+ cells/µL on day 2 to day 1. However, because apheresis variables and growth factor dose during collection were manipulated to optimize individual collections, the two regimens were not significantly different when the mean total CD34+ cells ×10(6) /kg collected was compared. Thus, when evaluating a chemotherapy regimen or new growth factor for mobilization, it is important to realize that total CD34+ cells collected is dependent on both mobilization and collection variables.

HLA-DR-DQ associations, combined with PLASMIC score, are reliable predictors of acquired thrombotic thrombocytopenic purpura (aTTP) and aid in differentiating aTTP from other thrombotic microangiopathies.

BACKGROUND: Thrombotic microangiopathies (TMA) are a group of disorders with overlapping clinical features that require urgent intervention. Treatment is based on the recognition of the TMA type, which is often challenging. The aim of this study was to identify specific HLA associations with different TMA types to aid rapid diagnosis and appropriate treatment, since the HLA assay can be completed within five hours. METHODS: All 86 consecutive patients who presented to the University of Arkansas for Medical Sciences between May 2013 and January 2021 with a presumptive diagnosis of TMA were included in this study. HLA typing was performed and correlated with other clinical and laboratory studies. RESULTS: In comparison with other types of TMA, patients with acquired thrombotic thrombocytopenic purpura (aTTP) showed increased frequencies of HLA-DRB1*11, HLA-DQB1*03:01/19, HLA-DRB1*08 and HLA-DRB3. Combining the presence of these HLA associations with a PLASMIC score of 6 or more achieved a higher positive predictive value (90%) for identifying aTTP than the PLASMIC score alone (69%). In comparison with other TMA types, patients with aTTP showed decreased frequencies of HLA-DRB4, HLA-DRB1*07, HLA-DQB1*02. The HLA-DRB1*07/DQB1*02 was not observed in any aTTP patients (negative predictive value: 100%), and thus the presence of this haplotype essentially rules out aTTP. Further, HLA-DRB1*11/DQB1*03:01/19 was absent in atypical hemolytic uremic syndrome patients. CONCLUSION: HLA alleles can be used as an adjunct for the rapid assessment of TMA and can help to differentiate it from other primary and secondary forms of TMA, allowing for earlier definitive therapy.

Three years of maintenance with VRD in multiple myeloma: results of total therapy IIIB with a 15-year follow-up.

ABSTRACT: The total therapy (TT) IIIB phase 2 study incorporated bortezomib into tandem melphalan-based hematopoietic stem cell transplantation with dexamethasone, thalidomide, cisplatin, doxorubicin, cyclophosphamide, and etoposide for induction/consolidation and bortezomib, lenalidomide, and dexamethasone (VRD) for maintenance in patients with newly diagnosed multiple myeloma (MM). This updated analysis presents a 15.4-year median follow-up. Of 177 patients, 21% patients had gene expression profile (GEP)-defined high-risk MM. 15-year progression free survival (PFS) was 27.9%. Median PFS was better in GEP-defined low-risk patients at 7.8 years and in International Staging System stage 1 patients at 8.7 years. Overall, median OS was 9.1 years, and 15-year overall survival (OS) was 35.9%. GEP-defined low-risk patients' median OS was 11.2 years, and that of GEP-defined high-risk patients was 2.8 years. There was no difference in OS between TT IIIB and TT IIIA. This study includes the longest follow-up of patients treated with maintenance VRD reported to date. In patients with GEP-defined low-risk, nearly half and one-third of patients without ongoing treatment showed no signs of progression at 10 and 15 years, respectively. One-third of patients survived more than 15 years, but 3 years of VRD maintenance did not improve outcomes for patients with GEP-defined high-risk MM. The study was registered on www.clinicaltrials.gov as #NCT00572169.

A case of acquired dysfibrinogenemia in multiple myeloma treated with therapeutic plasma exchange.

A 70 year old Caucasian woman with IgG lamda multiple myeloma presented with uncontrollable bleeding from a bone marrow biopsy site which started days after the procedure. The patient was hyperviscous, and coagulation tests showed elevated activated partial thromboplastin time (aPTT) which was not corrected with a mixing study, elevated thrombin time and reptilase time, and possible inhibitors to Factors VIII and IX. Therapeutic plasma exchange was performed using plasma with corrections of plasma viscosity (1.6 to 1.1 centipoise) and aPTT (50 to 42.1s) observed. The bleeding was controlled, and purified IgG demonstrated dysfibrinogenemic effects of the patient's paraprotein.

Validation of a formula for predicting daily CD34(+) cell collection by leukapheresis.

BACKGROUND AIMS: The ability to predict how many CD34(+) cells a donor will collect on a given day is vital for efficient leukapheresis. METHODS: We validated a formula to predict daily CD34(+) cell collections by leukapheresis, calculated as follows: (peripheral blood CD34(+) cells/L) × (adjusted collection efficiency of 30%)/body weight (kg), multiplied by the number of liters processed. This validation was performed from 234 donors undergoing 30 L large volume leukapheresis (LVL) and 162 donors undergoing smaller collections (non-LVL). The LVL group consisted of 811 collection events (625 multiple myeloma, 186 non-myeloma). The non-LVL group consisted of 224 collection events (196 multiple myeloma, 28 non-myeloma). All predicted and observed CD34(+) cell collection numbers were plotted (predicted versus observed) and assessed using linear regression analyses. Linear correlation coefficients (r-values), slopes and intercepts of the regression lines were evaluated. RESULTS: Predicted versus observed data points across all quantities of CD34(+) cells/kg collected by both LVL and non-LVL had strong r-values of 0.947 and 0.913, respectively, demonstrating near perfect positive linear correlations. Data for LVL collections subgrouped by number of cells collected (poor, intermediate and good), mobilization regimen, collection day and diagnosis were analyzed the same way and showed consistent findings. CONCLUSIONS: We have validated a formula with a strong ability to predict collection of CD34(+) cells/kg that would allow for individualization of collection for any donor once the peripheral blood CD34(+) cell count and optimal goal of collection were known; to date this has not been published by other groups.

Aldehyde dehydrogenase as an alternative to enumeration of total and viable CD34(+) cells in autologous hematopoietic progenitor cell transplantation.

We validated the correlation of aldehyde dehydrogenase ALDH(br) cells with total and viable CD34(+) cells in fresh and thawed hematopoietic progenitor cell (HPC) products, and looked for a correlation with time to white blood cell (WBC) and platelet engraftment after autologous transplantation, using simple linear regression analyzes. We found a significant correlation between pre-freeze ALDH(br) cell numbers and pre-freeze total CD34(+) (P < 0.001), viable CD34(+) (P < 0.001) and post-thaw viable CD34(+) (P < 0.001) cell numbers. We suggest that ALDH(br) may be substituted for CD34(+) cell numbers when evaluating HPC. As post-thaw viability testing apparently adds no significant information, we suggest that it may not be necessary. Finally, neither marker correlated with time to engraftment in our patients, supporting previous data suggesting the existence of a threshold dose for timely engraftment around 2.5 × 10(6) cells/kg.

A comparison of washed and volume-reduced platelets with respect to platelet activation, aggregation, and plasma protein removal.

BACKGROUND: Washed or volume-reduced platelets (PLTs) are occasionally requested for patients with a history of allergic or anaphylactic transfusion reactions. However, conclusive data are not available as to which method is more suitable. STUDY DESIGN AND METHODS: A direct comparison of saline-washed and volume-reduced PLTs was performed by splitting 11 units of 6-day-old apheresis PLT units. PLT activation, aggregation, plasma protein, and PLT count were determined before and after each procedure. To assess whether washing using neutral, calcium-free Ringer's acetate (NRA) would better preserve PLT function, 8 additional units of apheresis PLTs were split and were washed in saline or NRA. RESULTS: Saline washing resulted in significantly increased number of activated, P-selectin-expressing PLTs compared to volume reduction (24.2% vs. 10.3%, p = 0.001). Aggregation was also significantly reduced (-40.6% vs. -0.8%, p = 0.004). Plasma protein removal was significantly better for saline-washed than volume-reduced PLTs (96% vs. 51.1%, p < 0.001). PLT recovery was not significantly different for saline-washed versus volume-reduced PLTs (70.5% vs. 80.7%, p = 0.079). There was no difference between washing in saline or NRA with regard to PLT activation and loss of aggregation. CONCLUSIONS: PLT washing with saline or NRA significantly increases PLT activation and decreases PLT aggregability. On the other hand, volume reduction does not adequately remove plasma proteins. Therefore, PLT washing should be reserved for patients with a history of severe allergic or anaphylactic transfusion reactions. We suggest that fresher PLTs be selected to improve the functionality of washed PLTs.

Optimizing dendritic cell-based immunotherapy in multiple myeloma: intranodal injections of idiotype-pulsed CD40 ligand-matured vaccines led to induction of type-1 and cytotoxic T-cell immune responses in patients.

Vaccination with idiotype (Id) protein-pulsed dendritic cells (DCs) has been explored in multiple myeloma and the results have been disappointing. To improve the efficacy of DC vaccination in myeloma, we investigated the use of Id- and keyhole limpet haemocyanin (KLH)-pulsed, CD40 ligand-matured DCs administered intranodally. Nine patients with smouldering or stable myeloma without treatment were enrolled and DC vaccines were administered at weekly intervals for a total of four doses. Following vaccination, all patients mounted Id-specific gamma-interferon T-cell response. Interleukin-4 response was elicited in two, and skin delayed-type hypersensitivity reaction occurred in seven patients. More importantly, Id-specific cytotoxic T-cell responses were also detected in five patients. Most if not all patients mounted a positive T-cell response to KLH following vaccination. At 1-year follow-up, six of the nine patients had stable disease, while three patients had slowly progressive disease even during the vaccination period. At 5-year follow-up, four of the six patients continued with stable disease. No major side effects were noted. In summary, intranodal administration of Id-pulsed CD40 ligand-matured DCs was able to induce Id-specific T and B-cell responses in patients. Current efforts are geared towards breaking tumour-mediated immune suppression and improving clinical efficacy of this immunotherapy.

Viability and engraftment of hematopoietic progenitor cells after long-term cryopreservation: effect of diagnosis and percentage dimethyl sulfoxide concentration.

BACKGROUND AIMS: We carried out a retrospective analysis of viability by diagnosis and dimethyl sulfoxide (DMSO) concentration in patients who had undergone autologous transplants using hematopoietic progenitor cells (HPC) after long-term storage (up to 17.8 years). METHODS: Viability was tested using flow cytometry for HPC that were harvested and preserved using a controlled rate freezer and 5% or 10% DMSO with human serum albumin, then stored in liquid nitrogen. Data from 262 samples were analyzed (249 myeloma patients and 13 other diagnoses): 100 consecutively thawed samples with a storage time of <1 year (all 10% DMSO), 50 consecutive samples stored for 1-4.9 years (10% DMSO), 50 samples stored for 5-9 years (5% DMSO) and all samples stored and used for transplant after >9 years (60 samples, 5% DMSO; two samples, 10% DMSO). RESULTS: No statistically significant difference in viability between the 5% DMSO and 10% DMSO groups was observed (P = 0.08), so the 1-4.9 years and 5-9 years were combined and the three groups (<1 year, 1-9 years and >9 years) were compared using an anova test. There was no difference in viability based on cryostorage period (P = 0.23) or between myeloma and other diagnoses (P = 0.45). No difference was seen in time to White blood cell (WBC) engraftment (P = 0.10) or to platelet engraftment between groups (P = 0.52). CONCLUSIONS: These data suggest that long-term storage in 5% DMSO and human serum albumin is safe.

Infusion of haplo-identical killer immunoglobulin-like receptor ligand mismatched NK cells for relapsed myeloma in the setting of autologous stem cell transplantation.

Killer immunoglobulin-like receptor (KIR)-ligand mismatched natural killer (NK) cells play a key role in achieving durable remission after haplo-identical transplantation for acute myeloid leukaemia. We investigated the feasibility of transfusing haplo-identical, T-cell depleted, KIR-ligand mismatched NK cells, after conditioning therapy with melphalan and fludarabine, to patients with advanced multiple myeloma (MM) followed by delayed rescue with autologous stem cells. No graft-versus-host disease or failure of autologous stem cells to engraft was observed. There was significant variation in the number of allo-reactive NK cells transfused. However, all NK products containing allo-reactive NK cells killed the NK cell target K562, the MM cell line U266, and recipient MM cells when available. Post NK cell infusion there was a rise in endogenous interleukin-15 accompanied by increasing donor chimaerism. Donor chimaerism was eventually lost, which correlated with the emergence of potent host anti-donor responses indicating that the immunosuppressive properties of the conditioning regimen require further optimization. Further, blocking of inhibitory KIR-ligands with anti-human leucocyte antigen antibody substantially enhanced killing of MM cells thus highlighting the potential for modulating NK/MM cell interaction. Encouragingly, 50% of patients achieved (near) complete remission. These data set the stage for future studies of KIR-ligand mismatched NK cell therapy in the autologous setting.

Mobilization of peripheral blood stem cells in myeloma with either pegfilgrastim or filgrastim following chemotherapy.

Quality and quantity of mobilized peripheral blood stem cells determine the safety of tandem autologous transplants in myeloma. Using the same mobilization chemotherapy with DT-PACE in two consecutive protocols, robustness of stem cell collection and rapidity of engraftment after transplantation were assessed. We employed either twice a day filgrastim versus two doses of pegfilgrastim. Advantages of pegfilgrastim were: (i) a higher percentage of patients collected 15x10(6)/kg in the first three days (p<0.001); (ii) the median number of CD34 cells/kg collected on day 1 was higher (p=0.004); (iii) the median number of growth factor injections was 2 versus 26 (p<0.0001); (iv) post-transplantation neutrophil recovery was faster after first and second transplant (p<0.001) and (v) platelet recovery was faster after first transplant (when less stem cells were infused) (p=0.01). Pegfilgrastim may be considered the standard of care for stem cell mobilization.

ADAMTS13 Testing Methodologies and Thrombotic Thrombocytopenic Purpura (TTP): Conflicting Results Can Pose a Clinical Dilemma.

ADAMTS13 testing plays a critical role in confirming the clinical diagnosis of acquired idiopathic thrombotic thrombocytopenic purpura (TTP) and distinguishing it from other forms of thrombotic microangiopathies (TMA). Serial measurements of ADAMTS13 activity and inhibitor levels are also helpful in determining response to treatment and/or subsequent relapses. Numerous ADAMTS13 assays have been developed recently, including some with rapid turnaround times. Despite the good inter-assay correlation of different ADAMTS13 methodologies in published case studies, discrepancies have been shown to occur. Here we present a case where discrepant results were obtained using two different assays, posing a clinical treatment dilemma.

Complement Regulatory Genetic Mutations in the Setting of Autoimmune Thrombotic Thrombocytopenic Purpura: A Case Series.

OBJECTIVE: To explore the benefits of adding eculizumab for the treatment of refractory autoimmune thrombotic thrombocytopenic purpura (iTTP) with complement dysregulation. PATIENTS AND METHODS: From January 1, 2014, through July 1, 2017, we identified patients with iTTP defined by ADAMTS13 (disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) levels less than 5% and the presence of ADAMTS13 inhibitor. Patients who progressed after receiving standard of care management for iTTP were subjected to a comprehensive evaluation to look for evidence of complement activation. Herein, we share our single-institute experience regarding the clinical course and treatment algorithm for 3 patients with refractory iTTP. RESULTS: All the patients had clinical deterioration despite treatment with plasma exchange, corticosteroids, rituximab, and vincristine, which prompted us to look for evidence of complement activation and associated genetic mutations. Complement-related genetic aberrations were present in all 3 patients, who had had different degrees of complement activation. The first 2 patients did not benefit from eculizumab when treatment was started before complete clearance of inhibitors to ADAMTS13. However, they had durable remissions when eculizumab was introduced after clearance of ADAMTS13 inhibitors. The third patient started eculizumab therapy after inhibitor levels were undetectable. CONCLUSION: We found eculizumab therapy to be effective in all 3 patients. However, its efficacy was prominent only after clearance of antibodies against ADAMTS13 via therapeutic plasma exchange.

M1 and M2 macrophages differentially regulate hematopoietic stem cell self-renewal and ex vivo expansion.

Uncovering the cellular and molecular mechanisms by which hematopoietic stem cell (HSC) self-renewal is regulated can lead to the development of new strategies for promoting ex vivo HSC expansion. Here, we report the discovery that alternative (M2)-polarized macrophages (M2-MΦs) promote, but classical (M1)-polarized macrophages (M1-MΦs) inhibit, the self-renewal and expansion of HSCs from mouse bone marrow (BM) in vitro. The opposite effects of M1-MΦs and M2-MΦs on mouse BM HSCs were attributed to their differential expression of nitric oxide synthase 2 (NOS2) and arginase 1 (Arg1), because genetic knockout of Nos2 and Arg1 or inhibition of these enzymes with a specific inhibitor abrogated the differential effects of M1-MΦs and M2-MΦs. The opposite effects of M1-MΦs and M2-MΦs on HSCs from human umbilical cord blood (hUCB) were also observed when hUCB CD34+ cells were cocultured with M1-MΦs and M2-MΦs generated from hUCB CD34- cells. Importantly, coculture of hUCB CD34+ cells with human M2-MΦs for 8 days resulted in 28.7- and 6.6-fold increases in the number of CD34+ cells and long-term SCID mice-repopulating cells, respectively, compared with uncultured hUCB CD34+ cells. Our findings could lead to the development of new strategies to promote ex vivo hUCB HSC expansion to improve the clinical utility and outcome of hUCB HSC transplantation and may provide new insights into the pathogenesis of hematological dysfunctions associated with infection and inflammation that can lead to differential macrophage polarization.