Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene.

The Northern Hemisphere experienced dramatic changes during the last glacial, featuring vast ice sheets and abrupt climate events, while high northern latitudes during the last interglacial (Eemian) were warmer than today. Here we use high-resolution aerosol records from the Greenland NEEM ice core to reconstruct the environmental alterations in aerosol source regions accompanying these changes. Separating source and transport effects, we find strongly reduced terrestrial biogenic emissions during glacial times reflecting net loss of vegetated area in North America. Rapid climate changes during the glacial have little effect on terrestrial biogenic aerosol emissions. A strong increase in terrestrial dust emissions during the coldest intervals indicates higher aridity and dust storm activity in East Asian deserts. Glacial sea salt aerosol emissions in the North Atlantic region increase only moderately (50%), likely due to sea ice expansion. Lower aerosol concentrations in Eemian ice compared to the Holocene are mainly due to shortened atmospheric residence time, while emissions changed little.

NSAID treatment with meloxicam enhances peripheral stem cell mobilization in myeloma.

Chemotherapy with G-CSF is used to mobilize peripheral stem cells in multiple myeloma (MM) patients, with plerixafor as a rescue strategy for poorly mobilizing patients. Preclinical studies suggested that the nonsteroidal anti-inflammatory drug meloxicam enhances the mobilization of CD34+ cells. In this single-center study, we evaluated whether adding meloxicam to chemotherapy/G-CSF mobilization increases peripheral hematopoietic CD34+ cell levels and reduces the need of using plerixafor. We prospectively compared two consecutive cohorts of MM patients in first remission mobilized with G-CSF and non-myelosuppressive chemotherapy with vinorelbine or gemcitabine. The second cohort additionally received oral meloxicam. The cohorts comprised 84 patients without meloxicam (-M) and 66 patients with meloxicam (+M). Meloxicam was well tolerated and associated with similar hematologic engraftment after transplantation and equal survival rates. However, the meloxicam group had higher CD34+ cell levels on day 8 of the mobilization procedure (53 200 versus 35 600 CD34+ cells/mL; P=0.007), and fewer patients needed >1 collection day (+M: 6 (9%) patients versus -M: 16 (19%) patients; P=0.04). This resulted in reduced plerixafor administrations (+M: 7 (11%) patients versus -M: 18 (21%) patients; P=0.03) and less costs. Our data suggest that meloxicam enhances the mobilization of hematopoietic CD34+ blood cells in MM patients.

Milk replacers supplemented with either L-arginine or L-carnitine potentially improve muscle maturation of early reared low birth weight piglets from hyperprolific sows.

As a result of the selection for genotypes with greater sow prolificacy, litter size increased and, concomitantly, average litter birth weight and early postnatal survival rates of low birth weight (L-BtW) offspring decreased. This study compared the impact of l-carnitine (CAR) and l-arginine (ARG) supplemented with a milk replacer and fed to L-BtW piglets born from large litters from days 7 to 28 of age on growth performance, carcass composition, organ and Semitendinosus muscle (STM) development. A total of 30 female and castrated Swiss Large White piglets weaned at 7 days of age were assigned to three milk replacer diets containing either no supplement (CON), CAR (0.40 g/piglet per day) or ARG (1.08 g/kg BW per day). Piglets were kept in pairs in rescue decks (0.54 m2). They were weighed daily and daily allowance of both, feed and ARG, was adjusted accordingly. Thus, feed allowance depended on growth. Each day, the milk replacer was prepared with water (1:4). Feed (allowance: 60 g dry matter/kg BW per day) was offered daily in six equal rations. Feed intake and feed efficiency was assessed for the pairs and apparent total tract-energy and -protein digestibility was determined from days 21 to 28 of age. On day 28, piglets were euthanized, blood samples were collected and the whole STM and organs were weighed. In STM, the size and metabolic properties of myofibers were determined. No difference in growth performance was found between dietary treatments, but piglets from the CAR group tended (P<0.10) to grow faster during the 1st experimental week and consume more feed from days 14 to 21 as compared with piglets of the CON group. A setback in growth in the last week in the CAR group coincided with the lower (P<0.05) energy and protein digestibility. Dietary treatments had no effect on STM and organ weight and myofiber size. Compared with the other groups, there were trends (P<0.10) for blood serum urea and glucose level to be greater in CAR and for non-esterified fatty acid level to be greater in ARG piglets. The greater (P<0.05) ratio of lactate dehydrogenase to either citrate synthase or ß-hydroxyacyl-CoA dehydrogenase indicated that the relative importance of the glycolytic compared with the oxidative pathway was greater in STM of CAR and ARG compared with CON piglets. These results suggest that ARG and CAR supplements were beneficial for muscle maturation whereas findings on phenotypic traits were rather unsystematic.

Morphometry of skeletal muscle capillaries: the relationship between capillary ultrastructure and ageing in humans.

AIM: To determine whether the ultrastructure of the capillary system in human skeletal muscle changes during advancing senescence, we evaluated the compartmental and subcompartmental organization of capillaries from vastus lateralis muscle (VL) biopsies of 41 non-diseased persons aged 23-75 years. METHODS: From each VL biopsy, 38-40 randomly selected capillaries were assessed by transmission electron microscopy and subsequent morphometry with a newly established tablet-based image analysis technique. RESULTS: Quantification of the compartmental organization revealed most indicators of the capillary ultrastructure to be only non-significantly altered (P > 0.05) over age. However, the peri-capillary basement membrane (BM) was thicker in the older participants than in the younger ones (P ≤ 0.05). Regression analysis revealed a bipartite relationship between the two parameters: a homogenous slight increase in BM thickness up to the age of approximately 50 years was followed by a second phase with more scattered BM thickness values. In 44.5% of the capillary profiles, projections/filopodia of the pericytes (PCs) traversed the BM and invaded endothelial cells (ECs) visible as PC pegs in pale cytoplasm holes (EC sockets). Strikingly, PC pegs were often in proximity to the EC nucleus. In PC profiles, sockets were likewise detected in 14.2% of the capillaries. Within these PC sockets, cellular profiles were frequently seen, which could be assigned to EC filopodia, internal PC curling or PC-PC interactions. Quantification of the occurrence of peg-socket junctions revealed the proportions of empty EC sockets and empty PC sockets to increase (P ≤ 0.05) during ageing. CONCLUSION: Our investigation demonstrates advancing senescence to be associated with increase in BM thickness and loss of EC and PC filopodia length in skeletal muscle capillaries.

Risk factors for pneumocystis pneumonia in giant cell arteritis: a single-centre cohort study.

OBJECTIVES: Pneumocystis jiroveci pneumonia (PCP) is a life-threatening opportunistic infection. Few PCP cases in giant cell arteritis (GCA) have been described, but it remains unknown, which patients need PCP prophylaxis. METHODS: Sixty-two patients with GCA from a prospective cohort were studied to identify treatment-related predictors of PCP infection. RESULTS: Four PCP infections occurred, all in patients treated with methotrexate in addition to prednisone. Moreover, PCP is associated with higher cumulative PDN doses and severe lymphocytopenia (<400/µl). CONCLUSIONS: Our findings support PCP-prophylaxis in GCA patients who are treated with methotrexate and PDN, and need high prednisone doses to achieve remission, or develop severe lymphocytopenia.

Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core.

Dust can affect the radiative balance of the atmosphere by absorbing or reflecting incoming solar radiation; it can also be a source of micronutrients, such as iron, to the ocean. It has been suggested that production, transport and deposition of dust is influenced by climatic changes on glacial-interglacial timescales. Here we present a high-resolution record of aeolian dust from the EPICA Dome C ice core in East Antarctica, which provides an undisturbed climate sequence over the past eight climatic cycles. We find that there is a significant correlation between dust flux and temperature records during glacial periods that is absent during interglacial periods. Our data suggest that dust flux is increasingly correlated with Antarctic temperature as the climate becomes colder. We interpret this as progressive coupling of the climates of Antarctic and lower latitudes. Limited changes in glacial-interglacial atmospheric transport time suggest that the sources and lifetime of dust are the main factors controlling the high glacial dust input. We propose that the observed approximately 25-fold increase in glacial dust flux over all eight glacial periods can be attributed to a strengthening of South American dust sources, together with a longer lifetime for atmospheric dust particles in the upper troposphere resulting from a reduced hydrological cycle during the ice ages.

Southern Ocean sea-ice extent, productivity and iron flux over the past eight glacial cycles.

Sea ice and dust flux increased greatly in the Southern Ocean during the last glacial period. Palaeorecords provide contradictory evidence about marine productivity in this region, but beyond one glacial cycle, data were sparse. Here we present continuous chemical proxy data spanning the last eight glacial cycles (740,000 years) from the Dome C Antarctic ice core. These data constrain winter sea-ice extent in the Indian Ocean, Southern Ocean biogenic productivity and Patagonian climatic conditions. We found that maximum sea-ice extent is closely tied to Antarctic temperature on multi-millennial timescales, but less so on shorter timescales. Biological dimethylsulphide emissions south of the polar front seem to have changed little with climate, suggesting that sulphur compounds were not active in climate regulation. We observe large glacial-interglacial contrasts in iron deposition, which we infer reflects strongly changing Patagonian conditions. During glacial terminations, changes in Patagonia apparently preceded sea-ice reduction, indicating that multiple mechanisms may be responsible for different phases of CO2 increase during glacial terminations. We observe no changes in internal climatic feedbacks that could have caused the change in amplitude of Antarctic temperature variations observed 440,000 years ago.

Crystal structure of the E. coli dipeptidyl carboxypeptidase Dcp: further indication of a ligand-dependent hinge movement mechanism.

Dcp from Escherichia coli is a 680 residue cytoplasmic peptidase, which shows a strict dipeptidyl carboxypeptidase activity. Although Dcp had been assigned to the angiotensin I-converting enzymes (ACE) due to blockage by typical ACE inhibitors, it is currently grouped into the M3 family of mono zinc peptidases, which also contains the endopeptidases neurolysin and thimet oligopeptidase (TOP). We have cloned, expressed, purified, and crystallized Dcp in the presence of an octapeptide "inhibitor", and have determined its 2.0A crystal structure using MAD methods. The analysis revealed that Dcp consists of two half shell-like subdomains, which enclose an almost closed two-chamber cavity. In this cavity, two dipeptide products presumably generated by Dcp cleavage of the octapeptide bind to the thermolysin-like active site fixed to side-chains, which are provided by both subdomains. In particular, an Arg side-chain backed by a Glu residue, together with two Tyr phenolic groups provide a charged anchor for fixing the C-terminal carboxylate group of the P2' residue of a bound substrate, explaining the strict dipeptidyl carboxypeptidase specificity of Dcp. Tetrapeptidic substrates are fixed only via their main-chain functions from P2 to P2', suggesting a broad residue specificity for Dcp. Both subdomains exhibit very similar chain folds as the equivalent but abducted subdomains of neurolysin and TOP. Therefore, this "product-bound" Dcp structure seems to represent the inhibitor/substrate-bound "closed" form of the M3 peptidases, generated from the free "open" substrate-accessible form by a hinge-bending mechanism. A similar mechanism has recently been demonstrated experimentally for ACE2.

High-resolution record of Northern Hemisphere climate extending into the last interglacial period.

Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 degrees C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time.

IL-10 transgenic mice present a defect in T cell development reminiscent of SCID patients.

To analyze the effect of IL-10 overexpressed by APCs as observed in some SCID patients, we have expressed the human IL-10 cDNA under the control of the murine MHC class II promoter in transgenic mice. Similar to SCID patients, these mice presented a defect in T cell maturation characterized by a rapid thymic aplasia that started after birth. The blockage in T cell maturation was strictly restricted to TCR-alpha beta T cells as the absolute number of thymic dendritic, TCR-gamma delta and NK1.1 T cells were equivalent to control littermates. Crossing IL-10 transgenic mice with TCR transgenic mice or treatment with staphylococcal enterotoxin B showed that the defect was not related to the impairment of positive or negative selection. However, repopulating of IL-10 transgenic mouse-fetal thymic organ culture with different stages of triple negative T cells isolated from control mice showed that the blockage occurred specifically at the pre-T cell stage and was reverted by treatment with blocking anti-IL-10 mAbs. These results demonstrate that IL-10 regulates T cell maturation and that dysregulation of IL-10 expression can lead to severe T cell immunodeficiency.

High spontaneous IL-10 production in unrelated bone marrow transplant recipients is associated with fewer transplant-related complications and early deaths.

Interleukin 10 (IL-10) is a potent inhibitor of proliferative T cell responses toward alloantigens, and suppresses the production of pro-inflammatory cytokines which are important in cellular activation and recruitment to sites of inflammation. Because of these properties, we hypothesized that high IL-10 production in patients prior to BMT may predict a better outcome. To investigate this, peripheral blood mononuclear cells (PBMNC) were obtained from 58 recipients (11 autologous, 25 related donor (RD), and 22 unrelated donor (URD)), prior to conditioning therapy. PBMNC were cultured for 24 h in the presence and absence of lipopolysaccharide (LPS) and culture supernatants were assayed for IL-10 using an ELISA method. Spontaneously produced and LPS-stimulated IL-10 levels were correlated with the development of transplant-related complications (TRC) including grade II-IV acute GVHD, veno-occlusive disease, idiopathic pneumonia syndrome and multi-organ dysfunction syndrome, and with death before day 100. For the autologous group, there were no TRC and only one death prior to day 100; therefore, no statistical comparisons to IL-10 levels could be made. In the RD group, 36% developed one or more TRC and 24% died before day 100; however, there were no statistically significant associations between spontaneous or LPS-induced IL-10 levels. In URD patients 41% developed TRC and 55% died prior to day 100. In this group, higher levels of spontaneous IL-10 production were associated with a lower overall occurrence of TRC (P = 0.03) and early death (P = 0.04). Our data would indicate that higher levels of IL-10 production prior to URD BMT may predict fewer TRC, as well as early deaths. The hypothesis that high IL-10 production prior to BMT may decrease complications following URD BMT warrants further testing.

A transgenic model to analyze the immunoregulatory role of IL-10 secreted by antigen-presenting cells.

IL-10 is a cytokine secreted by a wide variety of cells type that has pleiotropic stimulatory and suppressive activities on both lymphoid and myeloid cells in vitro. To analyze the consequences of high IL-10 secretion by APCs in immune responses, we produced transgenic mice expressing human IL-10 directed by the MHC class II Ea promoter. Despite alterations in the development of T and B cells, no gross abnormalities were detected in peripheral lymphocyte populations or serum Ig levels. However, when immunized using conditions that give either a Th2-type or a Th1-type response, IL-10 transgenic mice failed to mount a significant T or B cell immune response to OVA. IL-10 transgenic mice were also highly susceptible to infection with intracellular pathogens like Listeria monocytogenes or Leishmania major, in contrast to IL-10 transgenic mice, where the transgene was express in T cells. Finally, the recently described stimulatory effect of IL-10 on CD8+ T cells was confirmed by the ability of IL-10 transgenic mice to limit the growth of immunogenic tumors by a CTL-mediated mechanism. These results demonstrate, that, depending on the type of immune response, IL-10 can mediate immunosuppressive or immunostimulatory activities in vivo.

Inhibitory and stimulatory effects of IL-10 on human CD8+ T cells.

IL-10 is a well-documented immunosuppressant that inhibits macrophage-dependent Ag presentation and CD4+ T cell proliferation in vitro. We report that IL-10 inhibits alloantigen-specific proliferative responses and induces a long lasting anergic state in human purified CD8+ T cells when added concomitantly with the Ag in the presence of APC. Moreover, the generation of allospecific cytotoxic activity is inhibited by IL-10. These effects are indirect and are mediated through inhibition of the costimulatory functions of APC. In contrast, IL-10 has no direct inhibitory effects on the proliferation of purified CD8+ T cells activated by anti-CD3 mAb and promotes the growth of activated CD8+ T cells in combination with low doses of IL-2. Taken together, these results indicate that IL-10 has differential effects on CD8+ T cells depending on their state of activation, which may explain both the enhancing and inhibitory effects observed after IL-10 treatment in different in vivo experimental models.

A CD4+ T-cell subset inhibits antigen-specific T-cell responses and prevents colitis.

Induction and maintenance of peripheral tolerance are important mechanisms to maintain the balance of the immune system. In addition to the deletion of T cells and their failure to respond in certain circumstances, active suppression mediated by T cells or T-cell factors has been proposed as a mechanism for maintaining peripheral tolerance. However, the inability to isolate and clone regulatory T cells involved in antigen-specific inhibition of immune responses has made it difficult to understand the mechanisms underlying such active suppression. Here we show that chronic activation of both human and murine CD4+ T cells in the presence of interleukin (IL)-10 gives rise to CD4+ T-cell clones with low proliferative capacity, producing high levels of IL-10, low levels of IL-2 and no IL-4. These antigen-specific T-cell clones suppress the proliferation of CD4+ T cells in response to antigen, and prevent colitis induced in SCID mice by pathogenic CD4+CD45RB(high) splenic T cells. Thus IL-10 drives the generation of a CD4+ T-cell subset, designated T regulatory cells 1 (Tr1), which suppresses antigen-specific immune responses and actively downregulates a pathological immune response in vivo.

Interleukin-10 induces a long-term antigen-specific anergic state in human CD4+ T cells.

Human CD4+ T cells, activated by allogeneic monocytes in a primary mixed lymphocyte reaction in the presence of exogenous interleukin (IL) 10, specifically failed to proliferate after restimulation with the same alloantigens. A comparable state of T cell unresponsiveness could be induced by activation of CD4+ T cells by cross-linked anti-CD3 monoclonal antibodies (mAbs) in the presence of exogenous IL-10. The anergic T cells failed to produce IL-2, IL-5, IL-10, interferon gamma, tumor necrosis factor alpha, and granulocyte/macrophage colony-stimulating factor. The IL-10-induced anergic state was long-lasting. T cell anergy could not be reversed after restimulation of the cells with anti-CD3 and anti-CD28 mAbs, although CD3 and CD28 expression was normal. In addition, restimulation of anergized T cells with anti-CD3 mAbs induced normal Ca2+ fluxes and resulted in increased CD3, CD28, and class II major histocompatibility complex expression, indicating that calcineurin-mediated signaling occurs in these anergic cells. However, the expression of the IL-2 receptor alpha chain was not upregulated, which may account for the failure of exogenous IL-2 to reverse the anergic state. Interestingly, anergic T cells and their nonanergic counterparts showed comparable levels of proliferation and cytokine production after activation with phorbol myristate acetate and Ca2+ ionophore, indicating that a direct activation of a protein kinase C-dependent pathway can overcome the tolerizing effect of IL-10. Taken together, these data demonstrate that IL-10 induces T cell anergy and therefore may play an important role in the induction and maintenance of antigen-specific T cell tolerance.

Immune functions of cord blood cells before and after transplantation.

There have been numerous reports of decreased acute and chronic graft-versus-host disease in patients receiving HLA-matched or HLA-disparate umbilical cord transplants. It has been proposed that this may be due to the unique properties of the neonatal immune system, which permit the development of tolerance to alloantigens. This review discusses experimental evidence contrasting the immune functions of cells derived from cord blood and those from peripheral blood.

Dysfunctional cytokine production by host-reactive T-cell clones isolated from a chimeric severe combined immunodeficiency patient transplanted with haploidentical bone marrow.

We have investigated the mechanism of tolerance in a patient with severe combined immunodeficiency (SCID) transplanted with HLA-haploidentical, T cell-depleted bone marrow cells obtained from the mother. At 4 years after transplantation, T cells, natural killer (NK) cells, and a small percentage (2%) of B cells were found to be of donor origin, whereas monocytes and the majority of B cells remained of host origin. In primary mixed lymphocyte cultures (MLC), the engrafted T cells of the donor did not proliferate in response to the host cells, whereas untransplanted donor T cells showed good proliferative responses. However, CD4+ and CD8+ T-cell clones of donor origin with specificity for class II and class I HLA determinants of the host were isolated. CD8+, host-reactive T-cell clones displayed normal cytotoxic activity after stimulation with the host cells, but proliferative responses of CD4+, host-reactive T-cell clones were considerably reduced. In addition, both CD8+ and CD4+, host-reactive T-cell clones produced very low to undetectable levels of interleukin-2 (IL-2), IL-4, IL-5, IL-10, interferon-gamma, and granulocyte-macrophage colony-stimulating factor after specific antigenic activation, which may be responsible for their nonresponsive state in vivo. Expression of the CD3 zeta subunit of the T-cell receptor (TcR) was normal, and after stimulation via CD3, Raf-1 and p42 mitogen activated protein (MAP) kinase were phosphorylated, indicating that this part of the signaling pathway after triggering of the TcR/CD3 complex is present. These results, together with our previous observation that dysfunctional, host-reactive T-cell clones can be isolated in SCID patients transplanted with fetal liver stem cells, demonstrate that lack of clonal deletion of host-reactive T cells is a general phenomenon after HLA-mismatched stem cell transplantation.

HIV antibody testing and client retention in the therapeutic community. A preliminary report of Phoenix House.

This report describes the current approach to testing for the human immunodeficiency virus (HIV) antibody at Phoenix House, a large therapeutic community (TC) in the northeastern United States, and presents findings on retention of clients who have been tested for HIV antibodies and notified of their HIV serostatus. A total of 240 clients were tested while in treatment at Phoenix House between April 1988 and July 1992. Of these, 51 tested HIV positive. An additional 76 clients had tested positive for HIV antibodies prior to entering treatment. The difference in length of treatment stay between those who tested negative while in treatment and those who tested positive while at Phoenix House was not significant (t = 0.41, df = 238, p > .683). Although clients who tested seronegative during treatment were found to remain in treatment a significantly longer amount of time than the total population of seropositive clients (t = 4.54, df = 314, p < .001), those who learned of their seropositive status while in treatment remained in the program longer than clients who entered treatment aware of their seropositivity (t = 4.08, df = 125, p < .001). These findings suggest that acute reactions to the knowledge of seropositivity did not determine most premature terminations. The use of a small group, a core technical element of the TC, may have provided a favorable context for the task of HIV counseling and testing.

High levels of interleukin 10 production in vivo are associated with tolerance in SCID patients transplanted with HLA mismatched hematopoietic stem cells.

Transplantation of HLA mismatched hematopoietic stem cells in patients with severe combined immunodeficiency (SCID) can result in a selective engraftment of T cells of donor origin with complete immunologic reconstitution and in vivo tolerance. The latter may occur in the absence of clonal deletion of donor T lymphocytes able to recognize the host HLA antigens. The activity of these host-reactive T cells is suppressed in vivo, since no graft-vs. -host disease is observed in these human chimeras. Here it is shown that the CD4+ host-reactive T cell clones isolated from a SCID patient transplanted with fetal liver stem cells produce unusually high quantities of interleukin 10 (IL-10) and very low amounts of IL-2 after antigen-specific stimulation in vitro. The specific proliferative responses of the host-reactive T cell clones were considerably enhanced in the presence of neutralizing concentrations of an anti-IL-10 monoclonal antibody, suggesting that high levels of endogenous IL-10 suppress the activity of these cells. These in vitro data correlate with observations made in vivo. Semi-quantitative polymerase chain reaction analysis carried out on freshly isolated peripheral blood mononuclear cells (PBMC) of the patient indicated that the levels of IL-10 messenger RNA (mRNA) expression were strongly enhanced, whereas IL-2 mRNA expression was much lower than that in PBMC of healthy donors. In vivo IL-10 mRNA expression was not only high in the T cells, but also in the non-T cell fraction, indicating that host cells also contributed to the high levels of IL-10 in vivo. Patient-derived monocytes were found to be major IL-10 producers. Although no circulating IL-10 could be detected, freshly isolated monocytes of the patient showed a reduced expression of class II HLA antigens. However, their capacity to stimulate T cells of normal donors in primary mixed lymphocyte cultures was within the normal range. Interestingly, similar high in vivo IL-10 mRNA expressions in the T and non-T cell compartment were also observed in three SCID patients transplanted with fetal liver stem cells and in four SCID patients transplanted with T cell-depleted haploidentical bone marrow stem cells. Taken together, these data indicate that high endogenous IL-10 production is a general phenomenon in SCID patients in whom allogenic stem cell transplantation results in immunologic reconstitution and induction of tolerance. Both donor T cells and host accessory cells contribute to these high levels of IL-10, which would suppress the activity of host-reactive T cell in vivo.

Immune responses by cord blood cells.

In the present study, the biological properties of cord blood cells were investigated. Cord blood mononuclear cells and T cells responded normally to activation by alloantigens in primary mixed leukocyte reactions (MLRs), indicating that cord blood T cells can be normally activated via their TcR and have normal proliferative capacities. In addition, they expressed normal levels of accessory molecules such as CD28 and LFA-1, which contribute to amplify their responses. In contrast, cord blood mononuclear cells, but not cord blood monocytes, had a reduced capacity to stimulate allogeneic cells in primary MLRs. In addition, cord blood monocytes express lower levels of HLA-DR and ICAM-1 compared to adult peripheral blood monocytes. Cord blood mononuclear cells were also impaired in their capacity to generate allogeneic cytotoxic activity in primary mixed leukocyte cultures (MLCs). In contrast, cord blood B cells were similar to adult B cells in their capacity to switch to immunoglobulin E producing cells when incubated with interleukin-4 (IL-4) and anti-CD40 monoclonal antibody. We also demonstrated that IL-2, IL-6, and tumor necrosis factor-alpha (TNF-alpha) production by activated cord blood mononuclear cells was comparable to that observed with peripheral blood mononuclear cells isolated from normal adult donors. In contrast, interferon-gamma (IFN-gamma) was significantly decreased, whereas IL-4 and IL-5 were absent. Granulocyte-macrophage colony-stimulating factor (GM-CSF) levels were in general higher in the supernatants of cord blood cells. Thus, cord blood immune responses differ from those of peripheral blood at several levels. Whether these differences account for a reduced capacity of transplanted cord blood cells to modulate graft vs. host disease remains to be determined.