Expression of cytokine receptors by human cord blood lymphocytes: comparison with adult blood lymphocytes

Novel Anti Double-Stranded Nucleic Acids Full-Length Recombinant Camelid Heavy-Chain Antibody for the Detection of miRNA

The discovery that certain diseases have specific miRNA signatures which correspond to disease progression opens a new biomarker category. The detection of these small non-coding RNAs is performed routinely using body fluids or tissues with real-time PCR, next-generation sequencing, or amplification-based miRNA assays. Antibody-based detection systems allow an easy onset handling compared to PCR or sequencing and can be considered as alternative methods to support miRNA diagnostic in the future. In this study, we describe the generation of a camelid heavy-chain-only antibody specifically recognizing miRNAs to establish an antibody-based detection method. The generation of nucleic acid-specific binders is a challenge. We selected camelid binders via phage display, expressed them as VHH as well as full-length antibodies, and characterized the binding to several miRNAs from a signature specific for dilated cardiomyopathy. The described workflow can be used to create miRNA-specific binders and establish antibody-based detection methods to provide an additional way to analyze disease-specific miRNA signatures.

Potential of Cellular Therapy for ALS: Current Strategies and Future Prospects

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive upper and lower motor neuron (MN) degeneration with unclear pathology. The worldwide prevalence of ALS is approximately 4.42 per 100,000 populations, and death occurs within 3-5 years after diagnosis. However, no effective therapeutic modality for ALS is currently available. In recent years, cellular therapy has shown considerable therapeutic potential because it exerts immunomodulatory effects and protects the MN circuit. However, the safety and efficacy of cellular therapy in ALS are still under debate. In this review, we summarize the current progress in cellular therapy for ALS. The underlying mechanism, current clinical trials, and the pros and cons of cellular therapy using different types of cell are discussed. In addition, clinical studies of mesenchymal stem cells (MSCs) in ALS are highlighted. The summarized findings of this review can facilitate the future clinical application of precision medicine using cellular therapy in ALS.

Human Umbilical Cord Blood Cell Transplantation in Neuroregenerative Strategies

At present there is no effective treatment of pathologies associated with the death of neurons and glial cells which take place as a result of physical trauma or ischemic lesions of the nervous system. Thus, researchers have high hopes for a treatment based on the use of stem cells (SC), which are potentially able to replace dead cells and synthesize neurotrophic factors and other molecules that stimulate neuroregeneration. We are often faced with ethical issues when selecting a source of SC. In addition to precluding these, human umbilical cord blood (hUCB) presents a number of advantages when compared with other sources of SC. In this review, we consider the key characteristics of hUCB, the results of various studies focused on the treatment of neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis), ischemic (stroke) and traumatic injuries of the nervous system and the molecular mechanisms of hUCB-derived mononuclear and stem cells.

Humanized mice, a new model to study the influence of drug treatment on neonatal sepsis

Bacterial infection with group B Streptococcus (GBS) represents a prominent threat to neonates and fetuses in the Western world, causing severe organ damage and even death. To improve current therapeutic strategies and to investigate new approaches, an appropriate in vivo model to study the immune response of a human immune system is needed. Therefore, we introduced humanized mice as a new model for GBS-induced sepsis. Humanized mice feature deficiencies similar to those found in neonates, such as lower immunoglobulin levels and myeloid cell dysfunction. Due to the husbandry in specific-pathogen-free (SPF) facilities, the human immune cells in these mice also exhibit a naive phenotype which mimics the conditions in fetuses/neonates. Following infection, cytokine release and leukocyte trafficking from the bone marrow to the lymphoid organ (spleen) and into the peritoneum (site of infection) as well as bacterial spreading and clearance were traceable in the humanized mice. Furthermore, we investigated the effects of betamethasone and indomethacin treatment using this novel sepsis model. Although both drugs are commonly used in perinatal care, little is known about their effects on the neonatal immune system. Treatment of infected humanized mice not only induced the reduction of human leukocytes in the spleen but also increased the bacterial load in all analyzed organs, including the brain, which did not show infiltration of live GBS in untreated controls. These studies demonstrate the utility of the humanized mice as a new model to study an immature human immune response during bacterial infection and allow the investigation of side effects induced by various treatments.

Multiple intravenous administrations of human umbilical cord blood cells benefit in a mouse model of ALS

BACKGROUND

A promising therapeutic strategy for amyotrophic lateral sclerosis (ALS) is the use of cell-based therapies that can protect motor neurons and thereby retard disease progression. We recently showed that a single large dose (25 × 10⁶ cells) of mononuclear cells from human umbilical cord blood (MNC hUCB) administered intravenously to pre-symptomatic G93A SOD1 mice is optimal in delaying disease progression and increasing lifespan. However, this single high cell dose is impractical for clinical use. The aim of the present pre-clinical translation study was therefore to evaluate the effects of multiple low dose systemic injections of MNC hUCB cell into G93A SOD1 mice at different disease stages.

METHODOLOGY/PRINCIPAL FINDINGS

Mice received weekly intravenous injections of MNC hUCB or media. Symptomatic mice received 10⁶ or 2.5 × 10⁶ cells from 13 weeks of age. A third, pre-symptomatic, group received 10⁶ cells from 9 weeks of age. Control groups were media-injected G93A and mice carrying the normal hSOD1 gene. Motor function tests and various assays determined cell effects. Administered cell distribution, motor neuron counts, and glial cell densities were analyzed in mouse spinal cords. Results showed that mice receiving 10⁶ cells pre-symptomatically or 2.5 × 10⁶ cells symptomatically significantly delayed functional deterioration, increased lifespan and had higher motor neuron counts than media mice. Astrocytes and microglia were significantly reduced in all cell-treated groups.

CONCLUSIONS/SIGNIFICANCE

These results demonstrate that multiple injections of MNC hUCB cells, even beginning at the symptomatic disease stage, could benefit disease outcomes by protecting motor neurons from inflammatory effectors. This multiple cell infusion approach may promote future clinical studies.

Transplantation of umbilical cord blood stem cells for treating spinal cord injury

Spinal cord injury (SCI) develops primary and secondary damage to neural tissue and this often results in permanent disability of the motor and sensory functions. However, there is currently no effective treatment except methylprednisolone, and the use of methylprednisolone has also been questioned due to its moderate efficacy and the drug's downside. Regenerative medicine has remarkably developed since the discovery of stem cells, and many studies have suggested the potential of cell-based therapies for neural injury. Especially, the therapeutic potential of human umbilical cord blood cells (hUCB cells) for intractable neurological disorders has been demonstrated using in vitro and vivo models. The hUCB cells are immune naïve and they are able to differentiate into other phenotypes, including the neural lineage. Their ability to produce several neurotropic factors and to modulate immune and inflammatory reactions has also been noted. Recent evidence has emerged suggesting alternative pathways of graft-mediated neural repair that involve neurotrophic effects. These effects are caused by the release of various growth factors that promote cell survival, angiogenesis and anti-inflammation, and this is all aside from a cell replacement mechanism. In this review, we present the recent findings on the stemness properties and the therapeutic potential of hUCB as a safe, feasible and effective cellular source for transplantation in SCI. These multifaceted protective and restorative effects from hUCB grafts may be interdependent and they act in harmony to promote therapeutic benefits for SCI. Nevertheless, clinical studies with hUCB are still rare because of the concerns about safety and efficiency. Among these concerns, the major histocompatibility in allogeneic transplantation is an important issue to be addressed in future clinical trials for treating SCI.

Immune regulatory cells in umbilical cord blood and their potential roles in transplantation tolerance

Umbilical cord blood (UCB) is a source of primitive hematopoietic stem (HSC) and progenitor cells, that served as an alternative to bone marrow (BM) for effective transplantation therapy. Success of HSC transplantation (HSCT) is limited in part by graft-versus-host disease (GVHD), graft rejection and delayed immune reconstitution, which all relate to immunological complications. GVHD after UCB transplantation is lower compared to that of BM HSCT. This may relate to the tolerogenic nature of T cells, mononuclear cells (MNCs) and especially immune regulatory cells existing in UCB. UCB contains limiting numbers of HSC or CD34(+) cell dose for adult patients resulting in delayed engraftment after UCB transplantation (UCBT). This needs to be improved for optimal transplantation outcomes. Approaches have been undertaken to promote HSC engraftment, including co-infusion of multiple units of UCB cells. These new methods however added additional immunological complications. Herein, we describe current knowledge on features of UCB immune cells, including regulatory T cells (Tregs) and mesenchymal stem/stromal cells (MSCs) and their potential future usage to reduce GVHD.

Mankind's first natural stem cell transplant

The timing of the umbilical cord clamping at birth is still controversial. In the modern era of medicine, the cord has been clamped early to facilitate resuscitation and stabilization of infants. However, recently delayed cord clamping has been supported by physicians because it allows for the physiological transfer of blood from the placenta to the infant. Many clinical studies have revealed that the delayed cord clamping elevates blood volume and haemoglobin and prevents anaemia in infants. Moreover, since it was known that umbilical cord blood contains various valuable stem cells such as haematopoietic stem cells, endothelial cell precursors, mesenchymal progenitors and multipotent/pluripotent lineage stem cells, the merit of delayed cord clamping has been magnified. In this review, we discuss the advantages and disadvantages of delayed cord clamping at birth. We highlight the importance of delayed cord clamping in realizing mankind's first stem cell transfer and propose that it should be encouraged in normal births.

Human Umbilical Cord Blood Cell Grafts for Brain Ischemia

Irreversible and permanent damage develop immediately adjacent to the region of reduced cerebral blood perfusion in stroke patients. Currently, the proven thrombolytic treatment for stroke, tissue plasminogen activator, is only effective when administered within 3 h after stroke. These disease characteristics should be taken under consideration in developing any therapeutic intervention designed to widen the narrow therapeutic range, especially cell-based therapy. Over the past several years, our group and others have characterized the therapeutic potential of human umbilical cord blood cells for stroke and other neurological disorders using in vitro and vivo models focusing on the cells' ability to differentiate into nonhematopoietic cells including neural lineage, as well as their ability to produce several neurotrophic factors and modulate immune and inflammatory reaction. Rather than the conventional cell replacement mechanism, we advance alternative pathways of graft-mediated brain repair involving neurotrophic effects resulting from release of various growth factors that afford cell survival, angiogenesis, and anti-inflammation. Eventually, these multiple protective and restorative effects from umbilical cord blood cell grafts may be interdependent and act in harmony in promoting therapeutic benefits for stroke.

High-sensitivity immunofluorescence/flow cytometry: detection of cytokine receptors and other low-abundance membrane molecules

Cell marker identification by traditional phenotyping techniques is now considered straight-forward and relatively uncomplicated. In immunofluorescence/flow cytometry, the sensitivity, or detection limit, depends on the reagents, staining, and instrument parameters. The sensitivity of the most commonly used procedures, based on fluorescein-conjugated antibodies, approximately 2000 molecules of target antigen per cell, which is adequate for most of the widely used leukocyte markers. However, measuring target antigens of low density has proven very difficult indeed. Flow cytometric immunofluorescence is capable of detecting 100 molecules of target antigen per cell in practical applications, provided that every step of the staining and analysis procedure is optimized for sensitivity. This level of sensitivity reveals staining not seen using conventional analytical procedures. This unit discusses the underlying principles of high-sensitivity immunofluorescence and provides an excellent series of protocols for the practical detection of as few as 100 target antigen molecules per cell.

Infusion of human umbilical cord blood cells ameliorates hind limb dysfunction in experimental spinal cord injury through anti-inflammatory, vasculogenic and neurotrophic mechanisms

BACKGROUND

Human umbilical cord blood cells (HUCBCs) were used to investigate the mechanisms underlying the beneficial effects of cord blood cells in spinal cord injury (SCI).

METHODS

Rats were divided into three groups: (1) sham operation (laminectomy only); (2) Laminectomy+SCI+human adult peripheral blood mononucleocytes (PBMCs) (5 x 10(6)/0.3 mL); and (3) Laminectomy+SCi+HUCBCs (5 x 10(6)/0.3 mL). SCI was induced by compressing the spinal cord for 1 minute with an aneurysm clip calibrated to 55 g closing pressure. HUCBCs were infused immediately after SCI via the tail vein. Behavioral function tests measuring the maximal angle at which an animal could hold onto the inclined plane were conducted on days 1, 4 and 7 after SCI. Serum levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-10, were assayed. Furthermore, to determine if glial cell line-derived neurotrophic factor (GDNF) or vascular endothelial growth factor (VEGF) could be detected in the spinal cord injured area after systemic HUCBC infusion, analysis of these two molecules was conducted by immunofluorescence.

RESULTS

Systemic HUCBC infusion significantly attenuated SCI-induced hind limb dysfunction. The serum IL-10 levels were increased, but TNF-alpha levels were decreased after HUCBC infusion. Both VEGF and GDNF could be detected in the injured spinal cord after transplantation of HUCBC, but not PBMC, cells.

CONCLUSION

Our results demonstrate that HUCBC therapy may be beneficial for the recovery of SCI-induced hind limb dysfunction by increasing serum levels of IL-10, VEGF and GDNF in SCI rats.

Differing activation status and immune effector molecule expression profiles of neonatal and maternal lymphocytes in an African population

Higher susceptibility of newborns to infections has been attributed to the hypo-responsiveness of their cellular immune system. Here we compared the activation status and expression of cytokines and cytotoxic molecules of cord versus maternal peripheral blood mononuclear cells in an African population. Human leucocyte antigen-DR was expressed on a lower percentage of cord compared to maternal gammadelta and CD3(+) T cells. Similarly, a lower proportion of cord versus maternal gammadelta and CD3(+) T cells displayed perforin, granzyme B and cytokine activity either ex vivo or following non-specific stimulation in vitro. In contrast, comparable proportions of cord and maternal CD94(+) CD3(-) natural killer (NK) cells showed perforin and granzyme B expression ex vivo. We conclude that cord blood gammadelta and CD3(+) T cells are functionally hypo-responsive as reflected by reduced numbers of such cells expressing either an activation marker, T helper 1 (Th1) and Th2 cytokines or cytotoxic effector molecules. The similarity in numbers of cord and maternal CD94(+) CD3(-) cells expressing cytotoxic effector molecules suggests that neonatal Africans' NK cells may be functionally mature.

Maternal immunity provides protection against pertussis in newborn piglets

Pertussis continues to be a significant cause of morbidity and mortality in infants and young children worldwide. Methods to control the disease are based on vaccination with either whole-cell or acellular vaccines or treatment with antibiotics. However, despite worldwide vaccination infants are still at the highest risk for the disease. Here we used our newly developed newborn-piglet model to investigate whether transfer of maternal immunity can protect newborn piglets against infection with Bordetella pertussis. Pregnant sows were vaccinated with heat-inactivated B. pertussis or treated with saline (controls). Newborn piglets were allowed to suckle colostrum and milk for 4 to 5 days before they were challenged with 5 x 10(9) CFU of bacteria intrapulmonarily. Elevated levels of B. pertussis-specific secretory immunoglobulin A (S-IgA) and IgG antibodies were found in the colostrum and serum of vaccinated sows but not in those of control sows. Subsequently, significant levels of specific IgG and S-IgA were detected in the serum and bronchoalveolar lavage fluid of piglets born to vaccinated sows. Following infection with 5 x 10(9) CFU of B. pertussis, clinical symptoms, pathological alterations, and bacterial shedding were significantly reduced in piglets that had received passively transferred immunity. Thus, our results demonstrate that maternal immunization might represent an alternative approach to provide protection against pertussis in young infants.

Novel cell therapy approaches for brain repair

Numerous reports elucidate that tissue-specific stem cells are phenotypically plastic and their differentiation pathways are not strictly delineated. Although the identity of all the epigenetic factors which may trigger stem cells to make a lineage selection are still unknown, the plasticity of adult stem cells opens new approaches for their application in the treatment of various disorders. There is increasing researcher interest in hematopoietic stem cells for treatment of not only blood-related diseases but also various unrelated disorders including neurodegenerative diseases. Human umbilical cord blood (hUCB) cells, due to their primitive nature and ability to develop into nonhematopoietic cells of various tissue lineages, including neural cells, may be useful as an alternative cell source for cell-based therapies requiring either the replacement of individual cell types and/or substitution of missing substances. Here we focus on recent findings showing the robustness of adult stem cells derived from hUCB and their potential as a source of transplant cells for the treatment of diseased or injured brains and spinal cords. Depending upon the pathological microenvironment in which the hUCB cells are introduced, neuroprotective and/or trophic effects of these cells, from release of various growth or anti-inflammatory factors to moderation of immune-inflammatory effectors, may be more likely than neural replacement. These protective effects may prove essential to maintaining restored tissue integrity over the course of various diseases or injuries.

IL-1beta induces an exaggerated pro- and anti-inflammatory response in peritoneal macrophages of children compared with adults

Children have a lower incidence of acute lung injury (ALI) compared with adults. Because ALI appears to be the end result of systemic hyperinflammation, children may either have 1) an attenuated pro-inflammatory response or 2) an augmented anti-inflammatory response compared with adults. The purpose of this study was to determine the IL-1-induced pro- and anti-inflammatory response of pediatric vs. adult peritoneal macrophages (PMs). We hypothesized that pediatric PMs would have an enhanced anti-inflammatory response compared with adult PMs. Human PMs were collected during elective laparoscopic procedures, cultured, and stimulated with IL-1beta. IL-6, IL-8, IL-10, and TNFalpha production were determined by ELISA. Statistical analyses were by ANOVA; a P <0.05 was significant. Our results showed that IL-1beta induced an 11-fold increase in IL-10 production in pediatric PMs (659+/-103 vs. 60+/-25 control, P <0.05). There was no IL-10 production in IL-1beta-stimulated adult PMs. IL-1beta-induced TNF production was greater in children compared with adults (2152+/-166 vs. 592+/-188, P <0.05). Similarly, IL-1beta-induced IL-6 production was greater in pediatric PMs compared with adults (532+/-3 vs. 444+/-52, P <0.05). There was no difference in IL-1beta-induced IL-8 production in children compared with adults. The IL-10:TNFalpha ratio after IL-1beta stimulation was 0.306+/-0.056 in pediatric macrophages and 0.020+/-0.015 in adult macrophages ( P<0.01). In conclusion, IL-1beta-induced IL-6 and TNFalpha production were greater in pediatric than adult PMs. Furthermore, pediatric PMs had an 11-fold increase in IL-1beta-induced IL-10 production, while adult PMs did not produce IL-10. Therefore, IL-1beta induces both a pro- and an anti-inflammatory response in pediatric PMs, whereas adult PMs produce only pro-inflammatory cytokines in response to IL-1beta. The exaggerated anti-inflammatory IL-10 response in children may be an important factor in the observed differences in ALI between children and adults.

Functional responses of human neonatal B lymphocytes to antigen receptor cross-linking and CpG DNA

Human neonates are immunologically immature and consequently are highly susceptible to infection. The cellular basis for the dysfunctional immune responses of neonates is not clear, but is likely to reflect the immaturity of both B and T cell populations. Here we have examined the ability of human cord blood B cells to respond to antigen receptor cross-linking and also to CpG containing oligodeoxynucleotides (ODN), and compared their responses with those of adult peripheral blood B cells. Antigen receptor cross-linking with soluble F(ab')2 anti-IgM antibodies, induced HLA-DR and CD86 up-regulation and proliferation to a similar extent in adult and cord blood B cells. Both interleukin (IL)-2 and IL-4 co-stimulated anti-IgM-induced proliferation, but cord blood B cells were less sensitive than adult B cells to the co-stimulatory effects of IL-2. Antigen receptor cross-linking induced secretion of the chemokines macrophage inflammatory protein-1 alpha (MIP-1 alpha) and MIP-1 beta in adult and cord blood B cells, and secretion was enhanced by IL-2 or IL-4. CpG-ODN induced up-regulation of HLA-DR and CD86 expression and proliferation of adult and cord blood B cells, and anti-IgM and CPG-ODN synergized in the induction of proliferation. CpG-ODN also induced MIP-1 alpha and MIP-1 alpha secretion in adult and cord blood B cells. In addition to functional studies we examined the expression of CD62L (l-selectin), CCR7 and CXCR5. Our data show that surface expression of CD62L and CCR7 is lower on cord blood B cells than on adult B cells, suggesting that human cord blood B cells may exhibit homing defects.

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.

Development of interleukin-12-producing capacity throughout childhood

Increasing evidence indicates that the capacity to induce protective Th1 immune responses is impaired in early childhood, an observation that can be partially attributed to deficiencies in antigen-presenting-cell function. Synthesis of interleukin 12 (IL-12), a key Th1-trophic cytokine, is markedly reduced in the neonatal period, though there is a paucity of knowledge concerning the ontogeny of IL-12-synthetic capacity throughout the childhood years. Hence, we examined the production of bioactive IL-12 p70 by circulating mononuclear cells in a population of healthy individuals. As expected, the capacity to synthesize IL-12 p70 in response to either lipopolysaccharide or heat-killed Staphylococcus aureus was markedly impaired at birth, even after priming of cells with gamma interferon. Surprisingly however, IL-12 p70 synthesis by peripheral blood mononuclear cells from both 5- and 12-year-old children was still substantially below that seen in adults, and this did not appear to be related to excessive production of IL-10. In contrast, dendritic cells from adults and neonates, derived from monocytes with granulocyte-macrophage colony-stimulating factor and IL-4, synthesized equivalent amounts of IL-12 p70 in response to microbial stimulation. This indicates that the impaired capacity for IL-12 synthesis in childhood is not an intrinsic property of circulating mononuclear cells but rather can be readily overcome in response to appropriate maturational stimuli. Because IL-12 arose predominantly from circulating HLA-DR(+) cells that lacked B-cell- and monocyte-specific markers, we propose that the slow maturation of IL-12-synthetic capacity in the childhood years can be attributed to deficiencies in the number and/or function of dendritic cells.

Characterization of human CD25+ CD4+ T cells in thymus, cord and adult blood

CD4(+) CD25(+) regulatory T cells prevent organ-specific autoimmune diseases in various animal models. We analysed human lymphoid tissues to identify similar CD25(+) regulatory T cells. Adult peripheral blood contained two populations of CD4(+) T cells that expressed CD25 at different densities. The larger population (approximately 40%) expressed intermediate levels of CD25 (CD25(+)) and displayed a memory T-cell phenotype (CD45RA-/RO(+), CD45RB(low), CD95(+), CD62L(low), CD38(low)). The smaller population of cells (approximately 2%) expressed very high levels of CD25 (CD25(++)). In addition to the activation/memory T-cell antigens mentioned above they also expressed intracellular CD152 (CTLA-4) as well as enhanced levels of cell-surface CD122, similar to the murine CD4(+) CD25(+) regulatory counterpart. To exclude that the CD25(++) cells had not been recently primed by external antigen we analysed cord blood and thymus. CD25(++), CD152(+) and CD122(++) cells were present in paediatric thymus (10% of CD4(+) CD8(-) thymocytes) expressing signs of recent selection (CD69+) and in cord blood (5% of CD4(+) cells) where they showed a naive phenotype. In addition, cord blood contained a small population of CD25(+) cells (approximately 2% of CD4 T cells) that were CD152(-) and CD122(low) and displayed signs of activation. Together with published data that CD25(+) CD25(++) cells from the thymus and peripheral blood are regulatory, our results suggest that regulatory CD25(+) T cells leave the thymus in a naïve state and become activated in the periphery.

Phenotypic changes of T-lymphocyte subsets induced by interleukin-12 and interleukin-15 in umbilical cord vs. adult peripheral blood mononuclear cells

The decreased incidence of graft-vs.-host disease found following umbilical cord blood (CB) transplantation, and the increased susceptibility of newborns to infections, have been attributed, in part, to functional and phenotypic immaturity of neonatal T cells. We investigated the phenotypic changes of CB T cells induced by two immunoregulary cytokines, interleukin (IL)-12 and IL-15, alone or in combination. Adult peripheral blood (APB) mononuclear cells (MNCs) were also tested for comparison. Prior to culture, the percentages of CD3+ CD8+, CD3+ CD25+, and CD3+ CD56+ cells were significantly lower in CB MNCs than in APB MNCs. IL-15, but not IL-12, significantly increased CD3+ CD8+ expression among the CB MNCs after 1 week of culture. Combining IL-12 and IL-15, however, resulted in decreased CB CD3+ CD8+ expression compared with IL-15 alone. The percentage of CD3+ CD25+ cells in CB MNCs spontaneously increased in the absence of cytokines, while that of CD3+ CD56+ cells in CB MNCs could not be enhanced with cytokines. In contrast, the percentages of CD3+ CD25+ and CD3+ CD56+ cells among the APB MNCs could be increased with IL-12, IL-15, and further with IL-12 and IL-15 combined. Thus, different patterns of T-cell subset changes were demonstrated between CB MNCs and APB MNCs in response to IL-12 and/or IL-15. These data may serve as a foundation for using cytokine therapy in newborns and children receiving CB transplants.

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.

Cord blood leucocyte expression of functionally significant molecules involved in the regulation of cellular immunity

The cellular immune system of the newborn infant is immature and hypo-responsive when compared with adults. The extent to which immaturity of the leucocyte function underlies hyporesponsiveness in the newborn is incompletely understood. In this study flow cytometric techniques were applied to investigate the concurrent expression of a range of surface and intracellular leucocyte functional molecules and cytokines in resting and stimulated cord and adult blood. Production of interleukin (IL)-2 and expression of the components of its receptor, IL-2R alpha/beta/gamma, were investigated. No differences in the proportion of leucocytes producing IL-2R alpha and IL-2R gamma were observed for newborns and adults. A lower proportion of T cells and natural killer (NK) cells from newborns expressed IL-2R beta and upregulation of expression was slower. We hypothesize that reduced IL-2R beta may curtail early autocrine IL-2 activation of immune responses in the newborn. This hypothesis was supported by the observation that an increased proportion of stimulated T cells from newborns produced IL-2 at 4 h poststimulation, but at 24 h the proportion was lower than for adult T cells. The very low levels of interferon (IFN)-gamma produced by neonatal T cells and NK cells may also be partly explained by a curtailment of early autocrine activation of T cells. Expression and kinetics of upregulation for other functional molecules were studied. CD71, HLA-DR, tissue factor and CD152 levels were not significantly different for adults and newborns, suggesting that cord blood leucocytes, in some respects, may demonstrate functional maturity. IL-6 secretion by stimulated monocytes was also comparable in cord and adult blood. However, IL-1 alpha and IL-1 beta were produced by a lower proportion of monocytes from newborns than adults. Similarly, tumour necrosis factor (TNF)-alpha production for monocytes and T cells was lower in cord blood. The mean fluorescence intensity for IL-1 alpha, IL-1 beta and TNF-alpha was also lower for leucocytes from cord blood. These findings are significant in relation to the inability of newborn infants to mount a febrile response to infection. The findings of lower expression of IL-2R beta and lower production of inflammatory cytokines IL-1 alpha, IL-1 beta and TNF-alpha is a basis for improved understanding of the immunological immaturity of leucocytes in the newborn.

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.

Analysis of the human neonatal thymus: evidence for a transient thymic involution

The neonatal period is marked by the impairment of the major components of both innate and adaptive immunity. We report a severe depletion of cortical CD4+CD8+ double-positive thymocytes in the human neonatal thymus. This drastic reduction in immature double-positive cells, largely provoked by an increased rate of cell death, could be observed as early as 1 day after birth, delaying the recovery of the normal proportion of this thymocyte subset until the end of the first month of postnatal life. Serum cortisol levels were not increased in newborn donors, indicating that the neonatal thymic involution is a physiological rather than a stress-associated pathological event occurring in the perinatal period. Newborn thymuses also showed increased proportions of both primitive CD34+CD1- precursor cells and mature TCRalphabetahighCD69-CD1-CD45RO+/RAdull and CD45ROdull/RA+ cells, which presumably correspond to recirculating T lymphocytes into the thymus. A notable reinforcement of the subcapsular epithelial cell layer as well as an increase in the intralobular extracellular matrix network accompanied modifications in the thymocyte population. Additionally neonatal thymic dendritic cells were found to be more effective than dendritic cells isolated from children's thymuses at stimulating proliferative responses in allogeneic T cells. All these findings can account for several alterations affecting the peripheral pool of T lymphocytes in the perinatal period.

Occurrence of cytokine receptors on different lymphoid leukaemic cells

We have studied the expression of cytokine receptors CD25 (IL-2R alpha, 55 kD), CD116 (hGM-CSFR, 145 kD), CD117 (CSFR, 145 kD), CD120a (TNFR, 55 kD), CD120b (TNFR, 75 kD), CD121a (IL-1R, type I, 80 kD), CDw123 (IL-3R), CD124 (IL-4R, 140 kD), CD126 (IL-6R, 80 kD), CD127 (IL-7R, 75 kD), CDw128 (IL-8R), CD130 (gp130 subunit), CDw131 (common beta), CD132 (IL-2Rgamma), CD134 (OX40) and also CD95 (Fas antigen) on the lymphoid leukaemic cells. Cells from peripheral blood or bone marrow of 24 patients with disorders in lymphoid lineage mostly included acute lymphoid leukaemias (with a high leukocyte count and percentage of blasts) were analysed for the expression of surface membrane molecules by the immunofluorescence method evaluated by flow cytometry. The findings indicate that some monoclonal antibodies have a reactivity against cytokine receptors of pathological cells in individual cases, but with very variable qualitative and quantitative expression (number copies/cell). The lymphoid leukaemic cells demonstrate unique cytokine receptor profiles, which reveal the great diversity of immunophenotypes within the main functional characterisation of T and B lymphoproliferative malignancies.

Analysis of the cord blood T lymphocyte response to superantigen

We have characterized the T lymphocyte population of the human neonate in respect of the expression of phenotypic profiles for naive, memory and differentiated populations. We have examined the response of the neonate T cell to the superantigen Staphylococcus enterotoxin B (SEB) and compared the response to T cells from healthy adults. We found that the primary response to SEB is equivalent in neonates and adults but that the secondary response demonstrates hyporesponsiveness in the neonate that is more profound than in adults. This response was associated with increased expression of CD25; the alpha chain of the IL-2 receptor, equivalent to that seen in responding cells from adults. A modest increased expression of CD122 and CD132, the beta and gamma chains of the IL-2 receptor, was also observed. There was no increase in the IL-4 receptor (CD124). The hyporesponsive neonate T cells proliferated in response to exogenous IL-2 but the response was less than none SEB treated cells. The neonate cells did not respond to IL-4. We also examined the expression of MHC class II molecules on SEB stimulated cells and found that both neonate and adult T cells upregulate MHC class II to a similar degree. The difference in the hyporesponsive cells appears to result in part from a lower production of IL-2 and in part from a lower ability of cord cells to respond to IL-2. Since the stimulated cord cells expressed IL-2 receptor at the same levels as similarly treated adult cells; there may be differences in down stream signaling pathways.

Mononuclear cell subpopulations in preterm and full-term neonates: independent effects of gestational age, neonatal infection, maternal pre-eclampsia, maternal betamethason therapy, and mode of delivery

Blood samples from 29 preterm (24-32 weeks of gestation) and 21 full-term (37-42 weeks of gestation) neonates were analysed for surface markers of lymphocyte subtypes and macrophages, and the effects of gestational age, neonatal infection, maternal pre-eclampsia, maternal betamethason therapy and mode of delivery were assessed with multiple regression analysis. Gestational age alone had few independent effects (increase in CD3+, CD8+CD45RA+, and CD11alpha+ cells, and decrease in CD14+, HLA-DR- cells) during the third trimester on the proportions of the immune cell subtypes studied. Neonatal infection and mother's pre-eclampsia had the broadest and very opposite kinds of effects on the profile of immune cells in the blood. Infection of the neonate increased the proportions of several 'immature' cells (CD11alpha-CD20+, CD40+CD19-, and CD14+HLA-DR-), whereas mother's pre-eclampsia decreased the proportions of naive cell types (CD4+CD8+, CD5+CD19+). In addition, neonatal infection increased the proportion of T cells (CD3+, CD3+CD25+, and CD4+/CD8+ ratio, and CD45RA+ cells), while maternal pre-eclampsia had a decreasing effect on the proportion of CD4+ cells, CD4+/CD8+ ratio, and proportions of CD11alpha+, CD14+ and CD14+HLA-DR+ cells. Maternal betamethason therapy increased the proportion of T cells (CD3+) and macrophages (CD14+, CD14+HLA-DR+), but decreased the proportion of natural killer (NK) cells. Caesarean section was associated with a decrease in the proportion of CD14+ cells. We conclude that the 'normal range' of proportions of different mononuclear cells is wide during the last trimester; further, the effect of gestational age on these proportions is more limited than the effects of other neonatal and even maternal factors.

Interleukin 2 receptor regulation and IL-2 function in the human infant

IL-2 receptor is expressed at low levels on adult blood lymphocytes, and at lower levels on cord blood cells. IL-2 receptor alpha and beta chain expression increases gradually from 0-18 months of age. The level of soluble CD25 (IL-2 receptor alpha chain) has been reported to be elevated in cord blood. Quantitative RT-PCR showed that adult cells express 10 times as much CD25 mRNA as cord cells. Cord plasma showed only a marginal ability to strip CD25 from the membrane. To assess the functional consequences of low IL-2 receptor expression, cord and adult cells were activated in vitro. The response was stimulus-dependent, but cord cells upregulated CD25 readily. Cord and adult cells proliferated in an IL-2-dependent assay to a similar extent. Infants suffering acute infection showed marginally higher levels of membrane CD25 expression than infants without overt infection. Thus neonatal and infant lymphocytes express lower levels of IL-2 receptors than adult cells, reflecting lower mRNA concentrations at least for CD25; they are able to up-regulate receptors in response to in vitro stimulation and are able to respond in vitro to IL-2-dependent stimulation; however in vivo there may be a dampening down of the IL-2 system in infancy.

Differential cytokine regulation of natural killer cell-mediated necrotic and apoptotic cytotoxicity

Natural killer (NK) cells can kill target cells by either necrotic or apoptotic mechanisms. Using the 51Cr-release assay to measure necrotic death of target cells, neonatal NK cells had low NK activity (K562 targets) and high lymphokine-activated killer (LAK) activity (Daudi targets) compared with adult cells, as has been previously reported. Using a 125I-deoxyuridine (125I-UdR) release assay, cord cells were shown to also have higher apoptotic LAK activity against YAC-1 target cells. Interleukin-4 (IL-4) inhibited interleukin-2 (IL-2)-induced necrotic killing of target cells by adult effectors but had no such inhibitory effect on cord cells. In contrast, IL-4 inhibited both adult and cord LAK cytotoxicity of YAC-1 target cells by apoptotic mechanisms with higher suppression observed in cord cell preparations. Using a colorimetric substrate conversion assay, IL-2 induced higher, and IL-4 had a more significant suppressive effect on, cord cell granzyme B enzyme activity compared with adult cells, paralleling apoptosis cytotoxicity data. Co-culture of either adult or cord LAK cells with IL-4 had a similar inhibitory effect on granzyme B protein expression, as detected by Western blotting. In contrast, IL-4 did not inhibit perforin expression, thereby defining IL-4 as a cytokine that can differentially regulate the NK cell-mediated cytotoxicity processes of apoptosis and necrosis. The differential sensitivity of cord cells to cytokine regulation of cytotoxicity may also have implications for cord blood transplantations, as NK cells are known to function as an effector cell in both graft-versus-host disease and in the graft-versus-leukaemia phenomena.

Characterization of early activation events in cord blood B cells after stimulation with T cell-independent activators

Human neonates are immunologically immature, particularly in their humoral antibody responses to T cell-independent antigens, as exemplified by their increased susceptibility to infections with polysaccharide-encapsulated bacteria. To clarify the mechanism(s) underlying the unresponsiveness of neonates to polysaccharide antigens, we used an in vitro model with neonatal cord blood cells that has been shown to mimic surface Ig-dependent signaling in the adult by T cell-independent antigens. We studied the ability of cord blood human B cells to become activated after ligation of their surface Ig by unconjugated anti-Ig, dextran-conjugated anti-Ig, and Staphylococcus aureus Cowan A1, and compared their response with that of adult B cells. After the addition of nanogram concentrations of anti-Ig-dextran, neonatal cord blood B cells proliferated at levels comparable to that observed with adult B cells. The majority of cord blood B cells showed a marked rise in intracellular calcium, increased surface expression of human leukocyte antigen DR, and an increase in cell size. Direct activation of protein kinase C by phorbol esters in neonatal B cells led to cellular proliferation, and when combined with anti-Ig, a synergistic effect on proliferation was observed. These data suggest that the unresponsiveness of human neonates to polysaccharide antigens does not represent an inability of these antigens to induce early activation events in circulating B cells.

The development of antibody responses in the infant

The human infant is a major subject of immunization to prevent infectious disease. A better understanding of immune responses in human infants could lead to more effective immunization. Analysis of individual mechanisms is a prerequisite to understanding the whole response. We have examined the mutation and selection of immunoglobulin genes, mechanisms required for the maturation of antibody affinity. Mutations were rare in cord blood and were not detected in peripheral blood of infants under 10 days of age. Mutations were detected in most blood samples from infants aged 10 days to 2 months but the number of mutations was generally low compared with adults and there was limited evidence of selection. The ability to make and select mutated Ig increased over the 2-8 months period, but did not reach adult levels. Neonates differ from adults in the expression of several components of the immune system that may take part in affinity maturation, including cytokine receptors, antigen receptor and co-stimulator molecules. Thus, the mechanisms required to make high-affinity antibody develop gradually during the first year of life. Possible evolutionary reasons for this are discussed.

Postnatal changes in mucosal immune response: a physiological perspective of breast feeding and weaning

There are profound changes of immune activity during infancy from suppression during breast feeding, activation with weaning, and later intrinsic down-regulation after weaning. Breast feeding, as well as protecting against infections, seems to have a fundamental role in modifying the immune system against certain disease states. Transforming growth factor (TGF)beta in breast milk may mediate this immunosuppressive effect. Although the infant immune system is not in an adult state, the notion that the infant immune system is immature is difficult to reconcile with evidence that most infants respond appropriately to immunization and to infections. The systemic immune system of neonates may be subject to Th2 immune deviation, while the mucosal immune system, particularly of the gastrointestinal tract and probably the respiratory tract, is up-regulated with physiological inflammation during infancy. Weaning is associated with a peak of intestinal immune activation which includes mucosal mast cells and T cells. The physiological effects of this activation are promotion of epithelial growth of the small intestine and initial activation of mechanisms leading to subsequent down-regulation of the physiological heightened immune activity. This coincides with the development of mucosal (oral) tolerance to food and bacterial antigens.

Analysis of neonatal T cell and antigen presenting cell functions

Neonates are more susceptible to infection than adults and exhibit more intense or prolonged clinical symptoms. The extent to which deficiencies in T cell or antigen presenting cell (APC) function underlie hyporesponsiveness is incompletely understood. Here, immune function of cord blood mononuclear cells (CBMC), from healthy, full-term neonates was compared with adult PBMC. As widely reported, polyclonally-stimulated T cell proliferation was found to be equivalent, while IFN gamma responses were markedly lower amongst neonates. Reasoning that such stimuli may elicit responses qualitatively different from those that would be obtained following MHC-dependent, cognate T cell activation, alloantigen-specific responses were evaluated. Strikingly, neonates exhibited IFN gamma, IL-4 and IL-10 production equal to adults in short term primary culture. Both the frequency (Fisher's p < 0.0004) and intensity (< 7.5 vs 36.5 pg/ml; Wilcoxon P = 0.005) of alloantigen stimulated IL-5 responses were elevated among neonates, a finding equally evident using irradiated adult or neonatal cells as stimulators. Finally, the relative capacity of neonatal APC as stimulators of cytokine synthesis was assessed by a novel approach using CBMC as both responders and stimulators in MLR. Irradiated neonatal cells consistently stimulated similar proliferative but substantially lower IFN gamma responses than did adult APC, independent of responder origin. The data argue; (i) T cells are largely immunocompetent at birth, (ii) accessory cell function is not fully mature, and (iii) the widely observed hyporesponsiveness to pathogenes may be primarily due to immaturity of APC function or costimulator molecule expression.

The antigen receptor complex on cord B lymphocytes

The neonatal immune system responds to a restricted range of antigens, producing largely IgM antibody of low affinity. Comparison of the components of the B-cell antigen receptor complex shows significantly elevated membrane levels of IgM in neonatal B cells, compared with adult cells. CD79, which acts as the signal transducer for membrane immunoglobulin, is elevated in parallel with IgM, while IgD is elevated to a lesser degree. CD19, CD21, CD22 and CD81, which are all involved in transmitting activation signals when immunoglobulin is engaged, are not elevated. CD32, which is involved in negative regulation of activation, is present at reduced levels on cord B cells. The elevation of B-cell membrane IgM persists during infancy. Neonatal B cells respond in vitro to interleukin-4 (IL-4) by further elevation of membrane IgM levels. The elevated level of membrane IgM may make neonatal B cells easier to trigger by low concentrations of antigen, but in vitro activation and immunoglobulin modulation experiments did not show significant differences between cord and adult B-cell responses to anti-IgM.

Antigen-independent responsiveness to interleukin-4 demonstrates differential regulation of newborn human T cells

The low incidence of graft-versus-host disease following clinical use of umbilical cord blood compared to adult bone marrow as a source of stem cells for bone marrow reconstitution, leads to questions concerning the level of immunocompetence of newborn T cells. The maturation and functional status of newborn CD4+ T cells, which are almost exclusively CD45RA+ naive T cells, compared with their adult phenotypic counterparts, is poorly understood. We examined the proliferative response to mitogens and cytokines of CD4/CD45RA+ T cells from adults and newborns, with and without accessory cells. Newborn CD4/CD45RA+ T cells demonstrated a distinct proliferative response profile which was determined by the number of accessory cells present in co-cultures with various stimuli. Newborn CD4/CD45RA+ T cells were particularly responsive to interleukin (IL)-4, IL-4 plus anti-CD2 monoclonal antibodies (mAb) and IL-4 plus phytohemagglutinin (PHA), whereas adult CD4/CD45RA+ T cells were unresponsive under similar conditions. The mitogenic responses of newborn and adult CD4/CD45RA+ T cells to PHA and anti-CD2 mAb, which were equivalent, were directly proportional to the number of accessory cells present, whereas the responsiveness to cytokines was inversely proportional to the number of co-cultured accessory cells. Anti-CD2 responses were much more sensitive to low numbers of accessory cells than PHA. The particular sensitivity of newborn CD4/CD45RA+ T cells to IL-4 represents an antigen-independent T cell activation response which could help promote a Th2 immune response resulting in the newborn.

Decreased interleukin-10 production by neonatal monocytes and T cells: relationship to decreased production and expression of tumor necrosis factor-alpha and its receptors

The production of IL-10 by human neonatal blood mononuclear leukocytes (BML) stimulated with lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha), antibodies to CD3, or phorbol 12-myristate 13-acetate (PMA) was measured. The production of IL-10 by neonatal BML cultured with LPS or TNF-alpha was approximately 20 and approximately 15%, respectively, of adult BML. The combination of human recombinant TNF-alpha and LPS failed to augment IL-10 production in neonatal BML. The decreased production of IL-10 by neonatal leukocytes was not due to an autocrine feedback mechanism because only low concentrations of IL-10 were found in newborn sera. A connection with TNF-alpha could not be ruled out, because TNF-alpha production by LPS-stimulated newborn BML and the expression of TNF-alpha receptors on newborn monocytes were reduced. Mean +/- SD of concentrations of IL-10 in supernatants from adult and neonatal BML after stimulation with antibodies to human CD3 for 48 or 72 h were 914 +/- 386 and 178 +/- 176 pg/mL, respectively (p < 0.0001). In experiments with enriched populations of neonatal T cells, the addition of PMA failed to augment IL-10 production. This suggested that newborn T cells may be in a different state of activation than adult T cells Thus, IL-10 production in neonatal monocytes and T cells is reduced and this study suggests that the reduction may be secondary in part to regulatory processes involving TNF-alpha and its receptors.