Characterization of lymphocyte subpopulations in cord blood

Immunology of cord blood T-cells favors augmented disease response during clinical pediatric stem cell transplantation for acute leukemia

Allogeneic hematopoietic stem cell transplantation (HSCT) has been an important and efficacious treatment for acute leukemia in children for over 60 years. It works primarily through the graft-vs.-leukemia (GVL) effect, in which donor T-cells and other immune cells act to eliminate residual leukemia. Cord blood is an alternative source of stem cells for transplantation, with distinct biological and immunological characteristics. Retrospective clinical studies report superior relapse rates with cord blood transplantation (CBT), when compared to other stem cell sources, particularly for patients with high-risk leukemia. Xenograft models also support the superiority of cord blood T-cells in eradicating malignancy, when compared to those derived from peripheral blood. Conversely, CBT has historically been associated with an increased risk of transplant-related mortality (TRM) and morbidity, particularly from infection. Here we discuss clinical aspects of CBT, the unique immunology of cord blood T-cells, their role in the GVL effect and future methods to maximize their utility in cellular therapies for leukemia, honing and harnessing their antitumor properties whilst managing the risks of TRM.

Evolution and function of the ADP ribosyl cyclase/CD38 gene family in physiology and pathology

The membrane proteins CD38 and CD157 belong to an evolutionarily conserved family of enzymes that play crucial roles in human physiology. Expressed in distinct patterns in most tissues, CD38 (and CD157) cleaves NAD(+) and NADP(+), generating cyclic ADP ribose (cADPR), NAADP, and ADPR. These reaction products are essential for the regulation of intracellular Ca(2+), the most ancient and universal cell signaling system. The entire family of enzymes controls complex processes, including egg fertilization, cell activation and proliferation, muscle contraction, hormone secretion, and immune responses. Over the course of evolution, the molecules have developed the ability to interact laterally and frontally with other surface proteins and have acquired receptor-like features. As detailed in this review, the loss of CD38 function is associated with impaired immune responses, metabolic disturbances, and behavioral modifications in mice. CD38 is a powerful disease marker for human leukemias and myelomas, is directly involved in the pathogenesis and outcome of human immunodeficiency virus infection and chronic lymphocytic leukemia, and controls insulin release and the development of diabetes. Here, the data concerning diseases are examined in view of potential clinical applications in diagnosis, prognosis, and therapy. The concluding remarks try to frame all of the currently available information within a unified working model that takes into account both the enzymatic and receptorial functions of the molecules.

Cord blood stem cell transplantation for haemoglobinopathies

Despite improvements in supportive care, patients with beta-thalassaemia major or sickle cell disease (SCD) may benefit from haematopoietic stem cell transplantation at some point during their lives. Human leucocyte antigen (HLA)-matched sibling bone marrow donors are not always available and alternative sources of stem cells have been sought, including related and unrelated donor cord blood transplants (CBT). The outcome of CBT from related donors for the treatment of both thalassaemia major and SCD is now approaching that for bone marrow transplantation, with around 90% of patients surviving disease-free. The main complication is graft rejection, which may be reduced by increasing pretransplant immune suppression. Transplant-related mortality following HLA-identical matched related donor CBT is extremely low but is significant in the small series of unrelated and/or mis-matched donor CBT. The principal limitation to extending the use of CB stem cells for the cure of haemoglobinopathies is the need to better understand the mechanisms of action and optimal conditioning regimens used to secure long-term engraftment while minimizing morbidity and mortality. Further biological studies and clinical trials are needed to address this aim.

Human umbilical cord blood progenitor cells are attracted to infarcted myocardium and significantly reduce myocardial infarction size

We are investigating the effects of human umbilical cord blood mononuclear progenitor cells (HUCBC) for the treatment of acute myocardial infarction because human cord blood is a readily available and an abundant source of primitive cells that may be beneficial in myocardial repair. However, there is currently no scientific consensus on precisely when to inject stem/progenitor cells for the optimal treatment of acute myocardial infarction. We used an in vitro assay to determine the attraction of infarcted rat myocardium at 1, 2, 2.5, 3, 6, 12, 24, 48, and 96 h after left anterior descending coronary artery (LAD) occlusion from 45 rats for HUCBC in order to determine the optimal time to transplant HUCBC after myocardial infarction. Our assay is based on the migration of fluorescent DAPI-labeled HUCBC from wells in an upper chamber of a modified Boyden apparatus through a semiporous polycarbonate membrane into wells in a lower chamber that contain either normal or infarcted myocardium. DAPI-labeled HUCBC (100,000) were placed in each of the separate wells above the membrane that corresponded to normal or infarct homogenate in the lower wells. The greatest HUCBC migration to infarcted myocardium occurred at 2 h and 24 h after LAD occlusion in comparison with normal controls. A total of 76,331 +/- 3384 HUCBC migrated to infarcted myocardium at 2 h and 69,911 +/- 2732 at 24 h after LAD occlusion (both p < 0.001) and significantly exceeded HUCBC migration to normal heart homogenate. The HUCBC migration remained greatest at 2 and 24 h after LAD occlusion when the number of migrated cells was adjusted for the size of each myocardial infarction. Injection of 106 HUCBC in saline into infarcted myocardium of non immunosuppressed rats within 2 h (n=10) or at 24 h (n=5) after LAD occlusion resulted in infarction sizes 1 month later of 6.4 +/- 0.01% and 8.4 +/- 0.02% of the total left ventricular muscle area, respectively, in comparison with infarction sizes of 24.5 +/- 0.02% (n=10) in infarcted rat hearts treated with only saline (p < 0.005). Acute myocardial infarction in rats treated with only saline increased the myocardial concentration of tumor necrosis factor-alpha (TNF-alpha) from 6.9 +/- 0.8% to 51.3 +/- 4.6%, monocyte/macrophage chemoattractant protein (MCP-1) from 10.5 +/- 1.1% to 39.2 +/- 2.0%, monocyte inflammatory protein (MIP) from 10.6 +/- 1.6% to 23.1 +/- 1.5%, and interferon-gamma (INF-gamma) from 8.9 +/- 0.3% to 25.0 +/- 1.7% between 2 and 12 h after coronary occlusion in comparison with known controls (all p < 0.001). In contrast, the myocardial concentrations of these cytokines in rat hearts treated with HUCBC did not significantly change from the controls at 2, 6, 12, and 24 h after coronary occlusion. The present investigations suggest that infarcted myocardium significantly attracts HUCBC, that HUCBC can substantially reduce myocardial infarction size, and that HUCBC can limit the expression of TNF-alpha, MCP-1, MIP, and INF-gamma in acutely infarcted myocardium.

Evaluation of various methods of maternal placental blood collection for immunology studies

The collection of maternal placental intervillous blood (IVB), without contamination of fetal blood and with an accurate mononuclear cell profile, is essential for immunological studies of placental malaria and other infectious diseases of the placenta. We have compared five documented methods of IVB collection: perfusion, incision, biopsy, tissue grinding, and puncture (prick) for fetal blood contamination and mononuclear cell profiles using flow cytometry. Twenty-five placentas were obtained from Plasmodium falciparum and human immunodeficiency virus-negative primigravid and secundigravid women delivering at Nyanza Provincial Hospital in Kisumu, western Kenya. Each of the five methods was performed on the same placenta. Fetal red blood cell contamination was significantly lower for the prick and perfusion methods (4.1% and 8.3%, respectively) than for incision (59.5%), biopsy (42.6%), and tissue grinding (19.9%). Significant variation was noted among the five methods in the percentages of monocytes, total T cells, CD4+ and CD8+ T cells, B cells, and NK cells. Further, a pairwise comparison of prick and perfusion, the two methods with low fetal blood contamination, showed that they were not different for fetal red blood cell contamination levels; however, prick yielded significantly higher percentages of CD4 T cells and CD4 memory T cells than perfusion. Collection by prick was determined to be the best method of intervillous blood collection for immunology studies, and perfusion represented the next best method of choice due to high sample volume yield. Overall, in considering the advantages/disadvantages of the two methods with low fetal cell contamination, we conclude that a combination of prick and perfusion is most suitable for immunology studies.

Comparative flow cytometric analysis of term placental intervillous and peripheral blood from immediate postpartum women in Western kenya

Understanding maternal immune responses in the placenta is critical for management of pregnancy failures and haematogenous infections during pregnancy. However, it is unknown whether maternal placental intervillous blood (IVB) mononuclear cell populations are distinct from those found in maternal peripheral blood (PB). In this study, cell populations in the IVB and PB from immediate postpartum women were compared by flow cytometry. While levels of B and CD4+ and CD8+ T lymphocytes were similar, IVB contained significantly higher levels of monocytes (10.9+/-5.9 versus 5.5+/-2.5 per cent, respectively) and natural killer cells (14.3+/-9.6 versus 5.9+/-3.2 per cent, respectively) than the PB. Expression of the early activation marker CD69 was increased on T cells in the IVB, whereas levels of HLA-DR, a late activation marker, were similar between IVB and PB. These results suggest that maternal cells that circulate through the intervillous compartment may be subject to local influences that affect their distribution, phenotype and function. Further comparative study of these blood compartments will be necessary to elucidate the mechanisms by which the local placental milieu influences the IVB.

Activated umbilical cord blood cells from pre-term and term neonates express CD69 and synthesize IL-2 but are unable to produce IFN-gamma

BACKGROUND

The immune response exhibits quantitative and qualitative differences throughout human development. Both phenotypical and functional immaturity of newborn immune cellular components have been reported. We aimed to analyze possible differences in cellular activation assessed by expression of surface CD69 and cytokine production in mononuclear peripheral blood cells from premature (<37) and term (>37 weeks of gestation) neonates compared to adult donors.

METHODS

Ten persons from each group were selected; none was infected, immunodepressed, under medical treatment, or had any congenital abnormalities. Blood was obtained from umbilical cord of term and pre-term donors and vein punction of adults. All samples were collected in heparin and subsequently activated with PHA-L or PMA plus ionomycin at 37 degrees C for 4 h. After incubation, cells were labeled to determine CD69 expression on CD3+CD4+, CD3+CD8+, CD19+, and CD16+56+ subpopulations. Intracellular staining was performed to analyze IFN-gamma, IL-2, and CD69 in CD3+ cells. After staining, cells were analyzed by flow cytometry.

RESULTS

We first found a substantially higher number of CD3+CD4+CD69+ cells in premature and term neonates than in adults. Secondly, percentage of CD3+CD8+, CD56+, and CD19+ cells expressing CD69 was similar among the three groups. Thirdly, expression of CD69 was higher in CD19+ cells than in CD16+56+ cells of all three groups. Regarding cytokine production, IFN-gamma was detected only in cells from adults and was consistent in all individuals analyzed. In sharp contrast, IL-2 and intracellular CD69 (iCD69) were detected in all three groups, with no significant differences among them. Induction of IL-2 and iCD69 showed that lack of response with IFN-gamma was restricted to pre-term and newborn populations.

CONCLUSIONS

In summary, our results showed that a) CD69 is an early activation marker of both mononuclear umbilical cord and peripheral blood cells activated by a mitogenic stimulus, and b) newborn CD3+ cells probably lack conditions required to progress through the activation process that leads to IFN-gamma production. These conditions are still unknown but certainly constitute an interesting issue for further studies.

Expression of HLA-DR, CAM and co-stimulatory molecules on cord blood monocytes

Umbilical cord blood (CB) transplantations are associated with a lower risk of severe graft-versus-host disease (GVHD) compared to BMT. GVHD is an immune reaction that involves interaction between cell surface molecules resulting in cell activation and release of many cytokines. Monocytes are known to be an important source of cell adhesion (CAM) and co-stimulatory molecules which play a crucial role in the efficient activation of T and B cells. We analyzed the phenotype of CB monocytes in the presence or absence of an inflammatory signal (rIFN-gamma) and compared them to adult blood (AB); the expression of HLA-DR and 17 different markers (CD11a, CD11b, CD11c, CD18, CD29, CD40, CD44, CD49a, CD49d, CD49e, CD49f, CD54, CD58, CD62L, CD80, CD86 and CD102) was measured by flow cytometry. Statistical analysis showed that, compared to AB, CB monocytes did not express CD11b, CD11c, CD49d and after stimulation with rIFNgamma, they lost the expression of CD58 and CD102, whereas CD80 and CD86 expression was induced. The analysis of fluorescence intensity (MFI) revealed that CB monocytes expressed some CAM (CD29, CD54, CD102) with a lower intensity than AB monocytes except CD44. In conclusion, absence and reduced expression of some markers argue for a different phenotypic profile of CB monocytes compared to AB monocytes, which might partly contribute to their impaired immune response and to the low incidence of GVHD observed after CB transplantations. However, CB monocytes expressed CD80 and CD86 co-stimulatory molecules, but this expression did not prove a normal co-stimulatory function.

Can cord blood cells support the cytokine storm in GvHD?

Cord blood has a high number of proliferating hematopoietic progenitors and is therefore used as an alternative source of hematopoietic cells for allogeneic transplantation. In addition there is a wider availability of cord blood and a lower cost of procurement compared to bone marrow. However one of the most interesting immunological benefits of a cord blood transplant that has been proposed is the low severity of Graft versus Host Disease (GvHD). This review aims to address some of the immunological reasons why this may be the case by assessing the role of cord blood cytokines in the cytokine storm of GvHD.

Cord blood serum does not increase lymphocyte responses in comparison to adult serum

To date, over 1000 cord blood (CB) transplants have been reported from different centers worldwide and it is generally agreed that CB represents an encouraging alternative to bone marrow (BM) transplantation. There are a variety of reasons for this, however, possibly the two most controversial aspects are (a) whether there is less graft versus host disease (GVHD) with CB compared to BM transplantation, and (b) whether we can use more HLA mismatches with CB transplantation. The major theory regarding the reduced immunological response of CB lymphocytes is that CB T and NK cells are naive and, therefore, not primed for activation. However, the naive phenomena that has been noted in vitro may be bypassed in vivo by unforeseen factors. We show evidence that there are differences in the soluble factors present in CB and adult serum and that these differences play a role in T cell function. Thus, adult serum will enhance both mitogen and IL-2 specific T cell growth whereas CB serum has no effect, suggesting that there is an activation/growth factor present in adult sera, which is absent in CB sera. This work could enable us to identify the molecular mechanisms which are associated with a lower GVHD in CB compared to BM transplanted individuals.

Fetal natural killer cell function is suppressed

Previous studies have reported reduced natural killer (NK) cell activity in cord blood (CB) compared with adult blood mononuclear cell populations. Using a non-radioactive killing assay, we have verified these findings suggesting that either the fetal NK cell function is suppressed or that these cells are functionally immature. We have shown that CB NK cells are functional, since activating them with cytokines known to activate adult NK cells [interleukin-2 (IL-2), IL-12 and IL-15] increased activation. However, resting the cells, which enhanced adult NK cell activity (P < 0.01), had no effect on fetal NK cells (P = 0.2). These results suggested that fetal NK cells have the capacity to kill, but this is suppressed in vitro. This hypothesis was strengthened by our observation that eight of nine CB mononuclear cell populations had their NK activity restored by freeze-thawing, whereas four of five adult peripheral blood mononuclear cells had a reduced killing ability on freeze-thawing. Freeze-thawing removes a population of cells that suppresses CB NK cell function. To determine which was the case we performed extensive phenotypic analysis of the CB populations pre- and post-freezing and found that the percentage of the CD3- CD56+ population within CB increased significantly (P < 0.0005 by paired t-test) with freezing, whereas freeze-thawing had no effect on this population within a normal adult peripheral blood mononuclear cell population. Our data suggest that within CB there is a population of cells, as yet undefined, which may be inhibiting NK cell function. This report therefore shows clear differences between NK cells within the adult periphery and in CB, and may lead to a better understanding of events occurring in vivo.

Analysis of CD8+ T lymphocyte-mediated nonlytic suppression of autologous and heterologous primary human immunodeficiency virus type 1 isolates

Nonlytic CD8+ T lymphocyte antiviral factor (CAF) activity has been described as having an important role in the clinical course of human immunodeficiency virus type 1 (HIV-1) infection. Testing of CAF activity against autologous viruses isolated at approximately the same time points showed that CD8+ T lymphocytes from long-term survivors indeed possessed high CAF activity. However, in four of six progressors to AIDS, we observed the same amount of CAF activity in the face of increasing cellular HIV-1 load. In the other two progressors, CAF activity seemed preserved over time whereas the susceptibility of the virus isolate obtained late in infection seemed to be diminished. In a heterologous system, CAF activity of CD8+ T lymphocytes from 13 HIV-1-positive individuals did not correlate with CD4+ T lymphocyte counts. In two of three patients, syncytium-inducing (SI) HIV-1 variants, which are associated with a progressive clinical course, appeared to have a somewhat reduced susceptibility to CAF activity as compared to their coexisting non-SI HIV-1 variants. In a large donor group, suppression of SI isolates (as compared to non-SI isolates) mediated by heterologous CD8+ T lymphocytes was reduced. CD8+ T lymphocytes from five of six HIV-1-positive individuals suppressed HIV-1 replication in macrophages. CD8+ T lymphocytes from noninfected donors, even from cord blood, already had high CAF activity, suggesting that induction of this activity is neither virus nor HIV-1 specific.

Stem cells from bone marrow, umbilical cord blood and peripheral blood for clinical application: current status and future application

Bone marrow transplantation (BMT) has progressed rapidly during the past two decades to that of a treatment of choice as a therapeutically effective modality for the treatment of selected patients with malignant disease and non-malignant hematological disorders. However, its use is limited by availability of human leukocyte antigens (HLA)-matched donor cells, engraftment and graft-versus-host disease (GVHD). Prevention of GVHD, improvement in the speed and quality of marrow reconstitution, and screening of new immunomodulating agents which improve engraftment and augment hemopoiesis are intense areas of investigation. To this end there has clearly been progress in purification and characterization of human stem cells from different tissue sources. Discussed in this review are: (a) stem cell purification, characterization and ex vivo expansion; (b) bone marrow stem cell transplantation; (c) cord blood stem cell transplantation; (d) peripheral blood stem cell transplantation; (e) fetal liver stem cell transplantation; (f) in utero stem cell transplantation; and (g) evaluation of the capacity of stem cells to serve as targets for gene therapy.

Comparison of cord blood and adult blood lymphocyte normal ranges: a possible explanation for decreased severity of graft versus host disease after cord blood transplantation

Lymphocyte subpopulations in cord blood (CB; collected at birth from full-term babies) were compared with that of adult blood (AB) and found to contain significantly different numbers and percentages of lymphocyte subpopulations. The absolute lymphocyte count was greater in CB (4.8 +/- 1.1 x 10(9)/L) than in AB (1.69 +/- 0.38 x 10(9)/L), with CB having significantly higher absolute numbers of lymphocyte subsets even though CB percentages were significantly lower. Significant differences in percentages were found between cord and adult T cells (CB 58% vs AB 74%), NK cells (CB 19% vs AB 7%) and their subsets. CD38, a marker of activation and immaturity, was present on virtually all cord T cells and approximately half the adult T cells. CD45RA, a marker considered to define unprimed or naive cells, was expressed on 82% of cord lymphocytes as compared with 48% in AB. CD45RO was expressed on 16% of CB lymphocytes and 49% of AB lymphocytes. Cord blood contains a higher percentage and total number of immature and immunologically naive lymphocytes than AB.

Successful hematopoietic reconstitution with transplantation of erythrocyte-depleted allogeneic human umbilical cord blood cells in a child with leukemia

Cord blood, a potent source of hematopoietic stem cells, has been shown to successfully reconstitute hematopoiesis following allogeneic transplantation in a variety of disorders. A major drawback of cord blood has been the risk of transfusion reactions in ABO blood group incompatibility and drastic reduction in the stem cell pool if the cord blood is manipulated to remove red cells prior to cryopreservation or after thawing. This report describes an erythrocyte depletion method employing 3% gelatin-induced erythrocyte sedimentation for the selective removal of red cells from cord blood. The red cell-depleted fraction was shown to be enriched in progenitor cells and in cells secreting hematopoietic cytokines interleukin 3, granulocyte/macrophage colony-stimulating factor, and interleukin 6; a major source for cytokines was from cord T cells. This preparative technique was employed to separate out red cells from cord blood of an infant delivered by cesarean section who had an 8-year-old sibling with leukemia. Histocompatibility testing of cord cells revealed complete matching with the patient. A cord cell transplant of cryopreserved and thawed cells consisting of 4 x 10(7) nucleated cells per kg was administered to the patient following myeloablative chemotherapy. The patient's quick hematologic recovery and 9-month disease-free period to date suggest that 3% gelatin separation of erythrocytes is a simple method that can be successfully used for transplanting cord cells for malignant/nonmalignant diseases.

Does cord blood contain enough progenitor cells for transplantation?

We analyzed 125 blood samples obtained from umbilical cord immediately after delivery of full-term neonates. Between 0.1 and 10.4% (mean 1.13%, SD 1.34) of the density-separated glycophorin A (GPA)-negative mononuclear cells (MNC) expressed CD34 as analyzed by flow cytometry. These hematopoietic progenitor cells did not coexpress CD19, and the majority were negative for CD45RA. The number of MNC determined per ml cord blood ranged from 1 x 10(5) to 200 x 10(5) (mean 20.2 x 10(5), SD 24.7). Regression analysis revealed that a mean of 56% (n = 26, R = 0.8) and 120% (n = 35, R = 0.94) of the analyzed CD34+ MNC gave rise to day 14 colonies in the clonogenic assay when cultured without or with stem cell factor (SCF). The number and the exact phenotype of progenitor cells required for successful transplantation are not known. If the transplantation of 5 x 10(5) CD34% cells/kg body weight is required for engraftment and one-third of the progenitor cells are lost to cell processing, and if 180 ml blood can be collected from a single umbilical cord (and placenta), our data suggest that 90% of the collections do not contain enough precursors to transplant a 25 kg recipient. To meet these conditions, an average of 1439 ml cord blood would be necessary for transplantation.