Humoral and cellular immunity in humans studied at the cell level from birth to two years of age

Childhood diarrhoea in Danish day care centres could be associated with infant colic, low birthweight and antibiotics

AIM

Diarrhoea is very common in children attending day care centres. The aim of this study was to examine certain predisposing risk factors for an association with diarrhoea, including foreign travel, treatment with antibiotics, having household pets, infant colic, bottle feeding, using a pacifier and low birthweight.

METHODS

A dynamic one-year follow-up cohort study comprising 179 children from 36 day care centres was conducted from September 2009 to July 2013 in Copenhagen, Denmark. Questionnaires were sent to the children's parents or legal guardians every two months for a year, requesting information on gastrointestinal symptoms and exposure. A logistic regression was performed to identify the odds ratios of different risk factors for diarrhoea.

RESULTS

The odds ratios for diarrhoea were 1.97 (0.93-4.20) for children with a history of infant colic, 1.91 (0.90-4.04) for low birthweight children and 1.45 (0.74-2.82) for children who had used antibiotics. Having a pet in the household had a possible protective effect towards diarrhoeal events, with an odds ratio of 0.47 (0.20-1.09).

CONCLUSION

A history of infant colic, low birthweight, and to a lesser extent antibiotic use, possibly increased the risk of diarrhoea in Danish children in day care centres.

B lymphocyte subsets and their functional activity in the early months of life

In the present study we evaluated B-cell subsets and their functional development in 74 newborns from birth to 6 months of life. Moreover, we evaluated natural antibody production in vitro. The results documented a predominance of naive B-lymphocytes at all time-points evaluated, decreasing from birth to 6 months (p=0.009). The percentages of CD27+IgD+ and CD27+IgDneg memory B-cells were very low at birth and significantly increased only at 6 months (p=0.02 and p less than 0.001, respectively). We found a significant increase only in in vitro stimulated IgG production at 6 months as compared to birth (p less than 0.001). Moreover, a lower secretion of anti-Pn IgM antibodies up to 6 months of age, as compared to controls was observed. Our results underline that the susceptibility and severe course of infection in the neonate can be attributed, at least in part, to the lack of pre-existing immunological memory and competent adaptive immunity.

Immunoglobulin V(H) chain gene analysis of peripheral blood IgM-producing B cells in patients with Kawasaki disease

PURPOSE

Kawasaki disease is a systemic vasculitis, and its etiology and pathogenesis are still not clear. Our study was undertaken to investigate the characteristics of the activation of B cells in the peripheral blood of Kawasaki disease (KD) patients and evidence of stimulation by superantigens.

MATERIALS AND METHODS

Blood samples were obtained from three patients (2 males, 1 female) with KD, who were admitted to our Hospital, Seoul, Korea. The mean age was 1.2 years. Distribution of B cells was studied in the acute and subacute phases of KD patients. From the RNA of B cells, we obtained complementary DNA (cDNA) and performed polymerase chain reaction (PCR). To determine the oligoclonal expansion of immunoglobulin M (IgM) V(H) family, we cloned and sequenced the PCR products from each group and analyzed DNA.

RESULTS

In the peripheral blood of acute phase patients, T cells were significantly decreased (p < 0.05), whereas B cells were significantly increased (p < 0.05). When the first PCR was done on the B cell chains, V(H)1 to V(H)6 were all found to be expressed. The number of micro gene clones obtained from 3 patients was 312, and they belonged to V(H)3, V(H)4 and V(H)5 family. M99686 germ line was most frequently used and the next most frequently used, were X92224/J, L21967 and L21964. A similar order was seen in patients. Among the clones, 20 sets of clones showed the same base sequence and this was frequent between V(H)2 and V(H)5. There was one set, which showed almost the same base sequence between different patients, and the homology was 99.5%. Twenty sets of clones that had the same base sequence showed high similarity to the germ line (94 - 100%). Among these, the clones that utilized the M99686 germ line were 4 sets which were most frequent. The 3-dimensional structure of one of these clones showed typical beta, sheet structure of immunoglobulin chains.

CONCLUSION

The IgM transcripts expressed by the B cells in the peripheral blood of KD patients in the acute phase of the disease clearly showed an oligoclonal expansion, suggesting that KD is caused not by stimulation of a superantigen, but rather by a conventional antigen.

Intrapulmonary application of a 5-lipoxygenase inhibitor using surfactant as a carrier reduces lung edema in a piglet model of airway lavage

Leukotriene-generated effects on microvascular integrity and polymorphonuclear leukocytes (PMNL) play a key role in the inflammatory process of the alveolar-capillary unit in neonatal acute respiratory distress syndrome. We asked if intrapulmonary application of MK886, a 5-lipoxygenase inhibitor, and the use of a porcine surfactant preparation (Curosurftrade mark) as a carrier substance would improve lung function in a neonatal piglet model of airway lavage. Anesthetized, mechanically ventilated newborn piglets (n = 19) underwent repeated airway lavage to induce acute lung injury. Piglets then received either surfactant alone (S, n = 6), or MK886 admixed with surfactant (S + MK, n = 7), or an air-bolus injection as control (C, n = 6). Measurements of gas exchange, lung function, extravascular lung water (EVLW), cell counts, and leukotriene B(4) (LTB(4)) concentrations in bronchoalveolar lavage fluid (BAL) were performed during 6 hr of mechanical ventilation. Arterial oxygen partial pressure (PaO(2)) (S, 13.8 +/- 4.2 kPa, vs. S + MK, 20 +/- 6.6; P < 0.05), functional residual capacity (S, 15.1 +/- 6.8 ml/kg, vs. S + MK, 18.8 +/- 3.7 ml/kg; P < 0.05), and EVLW (S, 29 +/- 14 ml/kg, vs. S + MK 24 +/- 4 ml/kg; P < 0.05) were significantly improved in the MK886 group. This clinical effect was linked with a decrease in LTB(4) concentration in BAL (S, 3.5 (1.9-5.4) pg/ml, vs. S + MK, 1.6 (0.7-4.7) pg/ml; P < 0.05) and an increase in IL-8 (S, 2,103 (852-4,243) pg/ml, vs. S + MK, 3,815 (940-26,187) pg/ml; P < 0.05). PMNL counts in BAL were reduced (S, 570 +/- 42 cells/ml, vs. 275 +/- 35 cells/ml; P < 0.05). In conclusion, intrapulmonary application of the 5-lipoxygenase inhibitor MK886 with surfactant as a carrier improves lung function by decreasing EVLW as the main response to LTB(4) reduction.

Expression of toll-like receptors in neonatal sepsis

Despite recent identification of specific pattern recognition receptors (PRR) for distinct microbial structures, data indicating their relevance in human infectious diseases are limited. We determined the expression levels of the Toll-like receptor (TLR)2 and TLR4 by flow cytometry on granulocytes and monocytes of healthy neonates compared with healthy adults. The basal expression of TLR2 was only slightly lower in neonatal phagocytes, whereas no differences could be detected for TLR4. Analyzing neonates with sepsis, we found an impressive up-regulation of TLR2 on blood phagocytes already at initial presentation of symptoms. Comparison with C-reactive protein, IL-8, and IL-6 suggested that TLR2 expression on monocytes is comparably valuable as an early sepsis marker. TLR2 was differentially regulated during neonatal sepsis, showing a constant up-regulation on monocytes but only a transient increase on granulocytes. Surprisingly, TLR4 showed no remarkable changes. Our results revealed a mild deficiency of TLR2 expression in newborns and demonstrated a differential expression of TLR2 but not TLR4 in the course of neonatal sepsis, which could reflect specific inflammatory responses to distinct pathogens. The definition of TLR expression patterns might open a new field of therapeutic targets for neonatal sepsis.

Topical interleukin-8 antibody attracts leukocytes in a piglet lavage model

OBJECTIVE

Acute respiratory distress syndrome (ARDS) in young infants is linked with a pulmonary inflammatory response part of which are increased interleukin-8 (IL-8) levels and migration of polymorphonuclear leukocytes (PMNL) into lung tissue. A topical application of an antibody against IL-8 might therefore decrease PMNL migration and improve lung function.

DESIGN

Randomized, controlled, prospective animal study.

SETTING

Research laboratory of a university children's hospital.

SUBJECTS AND INTERVENTIONS

Anesthetized, mechanically ventilated newborn piglets (n=22) underwent repeated airway lavage to remove surfactant and to induce lung inflammation. Piglets then received either surfactant alone (S, n=8), or a topical antibody against IL-8 admixed to surfactant (S+IL-8, n=8), or an air bolus injection (control, n=6).

MEASUREMENTS AND RESULTS

After 6 h of mechanical ventilation following intervention, oxygenation [S 169+/-51 (SD) vs S+IL-8 139+/-61 mmHg] and lung function (compliance: S 1.3+/-0.4 vs S+IL-8 0.9+/-0.4 ml/cmH(2)O/kg; extra-vascular lung-water: S 27+/-9 vs S+IL-8 52+/-28 ml/kg) were worse in the S+IL-8 group because reactive IL-8 production [S 810 (median, range 447-2323] vs S+IL-8 3485 (628-16180) pg/ml; P<0.05) with facilitated migration of PMNL into lung tissue occurred. Moreover, antibody application caused augmented chemotactic potency of IL-8 [linear regression of migrated PMNL and IL-8 levels: S r(2)=0.30 (P=ns) vs S+IL-8 r(2)=0.89 (P=0.0002)].

CONCLUSION

Topical anti-IL-8 treatment after lung injury increases IL-8 production, PMNL migration, and worsens lung function in our piglet lavage model. This effect is in contrast to current literature using pre-lung injury treatment protocols. Our data do not support anti-IL-8 treatment in young infants with ARDS.

Species comparison of anatomical and functional immune system development

The components of the immune system have not been traditionally emphasized as potential target organs in standard developmental and reproductive toxicity (DART) protocols. A number of workshops have been organized in recent years to examine scientific questions that underlie developmental immunotoxicity tests, and the interpretation of results as they relate to human risk assessment. A key question that must be addressed is to determine the most appropriate species and strains to model the developing human immune system. The objective of this review is to compare the anatomical and functional development of the immune system in several species important to either preclinical studies for drug development or safety assessments for chemicals, with what is known in humans. The development of the immune system in humans will be compared to what is known in mice, rats, dogs and nonhuman primates.

Protective immunity of pneumococcal glycoconjugates

Pneumococcal polysaccharides (PSs), designated as T-cell independent type 2 (TI-2) antigens, induce poor immune responses in young children. Splenic marginal zone B cells, associated with CD21, CD19 and C3d, play an important role in TI-2 antibody responses, and provide host defense against bacterial pathogens. Antibody response, avidity, and opsonophagocytic activity of antisera were examined in mice immunized with type 9V PS conjugated to inactivated pneulmolysin (Ply) or to autolysin (Aly). Compared to mice given 9V PS alone, serum IgG and IgM concentrations against the 9V PS were higher in mice immunized with conjugates. High concentrations of serum antibodies were maintained for over 12 weeks. The relative avidities of IgG and IgM antibodies and opsonophagocytic activity against 9V pneumococci were high in mice immunized with conjugates. Thus, conjugate vaccines can induce high as well as long duration of antibody response and effective functional activity. In another study, mice received intranasal immunization with type 9V conjugate or 9V PS. These animals produced 9V PS IgG and IgA antibodies in their serum, spleen, intestine, lung, Peyer's patch and fecal extract samples. Mice immunized with these glycoconjugates exhibited opsonophagocytic activity and rapid bacterial clearance from blood and provided homologous and cross-protection against challenge with virulent pneumococci. These results indicate that intranasal immunization with glycoconjugate vaccines may serve as an alternative and convenient approach for prevention of pneumococcal infection.

Anti-interleukin-8 autoantibody in the tracheobronchial aspirate of infants with chronic lung disease

BACKGROUND

A high concentration of interleukin (IL)-8 has been observed in the tracheobronchial aspirate of infants with chronic lung disease (CLD), although the pattern varies depending on the type of CLD. Alveolar fluid from patients with adult respiratory distress syndrome (ARDS) also contains an elevated level of IL-8. Recently, the presence of anti-IL-8 autoantibody was demonstrated in the alveolar fluid from patients with ARDS.

METHODS AND RESULTS

The concentration of anti-IL-8 autoantibody in the tracheobronchial aspirate of infants with CLD was measured in order to discover whether there was any correlation with the concentration of IL-8. Similar to IL-8 concentration, the anti-IL-8 IgM antibody concentration in all infants with CLD following intrauterine infection was already high during the first 48 h. However, the concentration in infants with CLD following respiratory distress syndrome began to increase after 11 days of life, in contrast with the rise in IL-8 between 48 h after birth and day 5.

CONCLUSIONS

The presence of anti-IL-8 autoantibody may provide a mechanism that limits the bioavailability of free IL-8 in the lungs. In addition, the time lag between the increase in IL-8 and anti-IL-8 IgM autoantibody demonstrated in the present study could be used to estimate the time when the inflammation begins, even if the IL-8 concentration is already high.

Oligoclonal IgA response in the vascular wall in acute Kawasaki disease

Kawasaki Disease (KD) is a potentially fatal acute vasculitis of childhood. Although KD is the leading cause of acquired heart disease in children in developed nations, its pathogenesis remains unknown. We previously reported the novel observation that IgA plasma cells infiltrate the vascular wall in acute KD. We have now examined the clonality of this IgA response in vascular tissue from three fatal cases of KD to determine whether it is oligoclonal, suggesting an Ag-driven process, or polyclonal, suggesting nonspecific B cell activation or a response to a superantigen. We first sequenced VDJ junctions of 44 alpha genes isolated from a primary, unamplified KD vascular cDNA library. Five sets of clonally related alpha sequences were identified, comprising 34% (15 of 44) of the isolated alpha sequences. Furthermore, point mutations consistent with somatic mutation were detected in the related sequences. Next, using formalin-fixed coronary arteries from two additional fatal KD cases, we sequenced VDJ junctions of alpha genes isolated by RT-PCR, and a restricted pattern of CDR3 usage was observed in both. We conclude that the vascular IgA response in acute KD is oligoclonal. The identification of an oligoclonal IgA response in KD strongly suggests that the immune response to this important childhood illness is Ag-driven.

CD5-positive and CD5-negative human B cells converge to an indistinguishable population on signalling through B-cell receptors and CD40

Whether CD5 on B cells marks a subset functionally distinct from the conventional CD5 negative (CD5neg) adult population or is more an indicator of activation, remains contentious. Here we have investigated whether CD5 positive (CD5pos) and CD5neg B cells can be distinguished in terms of their response to surrogate signals aimed to model, in vitro, T-cell dependent (TD) and T-independent (TI) encounters with antigen in vivo: the predominantly CD5pos B-cell population found in cord blood, CD5 B cells positively selected from tonsils and their CD5neg counterparts, were compared. Neonatal B cells displayed a near-identical phenotype to that of adult CD5pos B cells, being characterized by uniform immunoglobulin M (IgM), immunoglobulin D (IgD), CD23 and CD44 coexpression. When cultured with anti-IgM maintained at high density on CD32-tranfected mouse L cells to model TI responses or on CD40 ligand (CD40L)-bearing L cells (with or without captured anti-IgM) to model TD encounters, DNA synthesis was stimulated to a similar extent in all three populations. Focusing on CD5 and CD23, we found that - although the signals delivered promoted distinct profiles of expression - under each condition of activation, the phenotypes that emerged for adult CD5pos and CD5neg B cells were remarkably similar. Neonatal B cells displayed a greater diminution in CD5 expression than adult CD5pos B cells following CD40 signals but otherwise the two populations again behaved similarly. The inclusion of interleukin-4 (IL-4) to cultures where cells were costimulated via surface (s)IgM and CD40 resulted in a complete loss of CD5 expression and a corresponding hyperexpression of CD23, irrespective of the population studied. The near-identical response of CD5pos and CD5neg B cells to surrogate TD or TI signals in vitro and their convergence to indistinguishable phenotypes is wholly supportive of CD5 being a fluctuating marker of activation rather than it delineating functionally distinct subsets.

Immune and hematopoietic reconstitution after transplantation of cord blood progenitor cells: case report and review of the literature

Transplantation using umbilical cord progenitor cells as the source of the stem cells is increasingly recognized as another form of allogeneic transplantation with curative intent. However, the different patterns of hematopoietic and immunological reconstruction have been described in very few patients. A 20-month-old boy presented with acute leukemia. He received standard AML induction and consolidation therapy, after which he underwent allogeneic transplantation using HLA-matched sibling stem cells obtained from the umbilical cord. The preparative regimen consisted of busulfan and cyclophosphamide. White cell recovery, despite concomitant use of G-CSF, was slow, reminiscent of the engraftment pattern without the use of growth factor. Erythroid recovery was best recorded using fetal cell HbF level. Platelet transfusion independence occurred on day +31. Immunologic reconstitution revealed an early NK cell recovery by 6 weeks and progressive T cell recovery until 3 months, with continued increase in counts thereafter. However, the CD4/CD8 ratio remained low even at 14 months post-transplantation. Recovery of B cells was slower until day +120. Proliferative response was within normal range on day +120. This report describes the unique engraftment pattern following umbilical cord blood transplant and emphasizes the pattern of immunological and hematological reconstitution.

Expression of the costimulator molecules, CD40 and CD154, on lymphocytes from neonates and young children

Differential expression of the costimulator molecules CD40 and CD154 on neonatal lymphocytes may be one explanation for limited T-dependent antibody responses in human neonates. CD40 was expressed at similar levels on resting B cells from adults, young children (2-20 months of age) or cord blood. CD40 expression was higher on cord blood B cells compared to adult B cells after stimulation with PMA and ionomycin, but similar on adult and cord blood B cells activated by CD3-stimulated T cells. In contrast to previous reports, cord blood T cells stimulated with PMA and ionomycin expressed adult levels of CD154 initially, but this expression was more transient on cord blood T cells. When adult and cord blood mononuclear cells were stimulated with CD3 mAb, T cells from some cord blood specimens showed different kinetics of CD154 expression compared with adult T cells. However, some cord blood specimens showed adult patterns of T cell CD154 expression. When mononuclear cells were depleted of B cells and monocytes prior to stimulation with CD3 mAb, the MFI and percentage of T cells expressing CD154 increased, with adult and cord T cells showing similar patterns of expression. These results show some differences in expression of CD40 and CD154 between neonatal and adult lymphocytes, but do not directly account for the relative deficiencies of humoral immunity in neonates.

Expression of the costimulator molecules, CD80, CD86, CD28, and CD152 on lymphocytes from neonates and young children

The expression of CD80, CD86, CD28, and CD152 were examined on peripheral blood lymphocytes from adults, neonates (cord blood lymphocytes) and young children (2-20 months of age). There was no difference in the expression of CD80 or CD86 between adult and neonatal B cells, either resting or activated. A higher percentage of resting T cells expressed CD28 in neonates and young children compared to adults. CD28 expression was similar on adult and neonatal T cells activated with PMA and ionomycin. However, CD28 was expressed at greater intensity on a higher percentage of neonatal T cells than adult T cells stimulated with CD3. CD152 expression was lower on neonatal T cells than adult T cells stimulated with PMA and ionomycin and undetectable on neonatal T cells stimulated with CD3. In contrast, intracellular CD152 was equivalent in adult and neonatal T cells stimulated with PMA and ionomycin, suggesting trafficking of CD152 to the cell surface may be differentially regulated in neonatal T cells. Since the T cell response is determined by the balance of signals received from CD28 and CD152, high levels of CD28 expression and lower surface expression of CD152 on neonatal T cells may represent specialisation to promote activation of neonatal T cells.

Rapid conversion of naive to effector T cell function counteracts diminished primary human newborn T cell responses

The reduced incidence of graft versus host disease following the use of human cord blood as a source of stem cells for bone marrow reconstitution challenges our understanding of the immunocompetence of newborn T cells. Newborn CD4+ T cells express mainly the CD45RA phenotype and have been considered to respond comparably to adult CD4+ T cells exhibiting the CD45RA phenotype. We compared the in vitro kinetics of phenotypic conversion of newborn and adult CD4+CD45RA+ T cells to CD4+CD45RO+ T cells. The cytokine profile and B cell helper activity of the converted CD4+CD45RO+ T cell population were also determined. Newborn CD4+CD45RA+ T cells were converted to CD4+CD45RO+ with significantly faster time kinetics than adult CD4+CD45RA+ T cells, following either phytohaemagglutinin (PHA) or anti-CD2 activation. Freshly purified newborn naive T cells did not produce IL-2, IL-4 or interferon-gamma (IFN-gamma) following stimulation, whereas adult naive T cells secreted IL-2 and adult-derived CD4+CD45RO+ T cells secreted all three cytokines under the same stimulatory conditions. However, newborn and adult CD4+CD45RA+ T cells, following primary stimulation and maturation in vitro, acquired the ability to secrete a Th1-type cytokine profile of IL-2 and IFN-gamma after secondary stimulation. Newborn CD4+ naive T cells that acquired the CD45RO phenotype in vitro also gained B cell helper activity equivalent to that of adult in vitro matured CD4+ naive T cells. These findings suggest that newborn and adult CD4+CD45RA+ T cell subsets are differentially responsive to various stimuli. They show that newborn CD4+CD45RA+ naive T cells can transform more quickly than their adult counterparts into functionally equivalent CD4+CD45RO+ T cells, a process that may be important to counteract the immature immune environment which exists in the newborn.

Ontogeny of the fetal immune system: study on pregnancies with Rh-isoimmunization and nonimmune fetal hydrops

This study aims at observing and comparing the antigen expression of some fetal T- and B-lymphocyte subpopulations in Rh-isoimmunization, which determines anemic hypoxia in the fetus, and nonimmune fetal hydrops (NIFH) which, even if there are some etiological factors involved, causes hipoxic hypoxia in the fetus. Twelve fetuses were studied by way of 30 fetal blood samples obtained by ultrasound-guided cordocentesis between the 20th and 36th gestational week. Twenty-four blood samples in all where taken from the eight fetuses with Rh-isoimmunization. Six blood samples were obtained from the four fetuses with NIFH. The lymphocyte phenotypes studied by monoclonal antibodies and flow cytometry were the following: CD3, CD4, CD8, expression of T-lymphocyte subpopulations; BsIg, CD19, expression of B-lymphocyte subpopulations. We observed a near-normal maturation process in fetuses with Rh isoimmunization, whereas in fetuses with NIFH we observed inhibition and/or delayed expression of T-lymphocytes. An early and increased B-lymphocyte activation marked a cooperation between the two systems in the early gestational periods.

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.

B Cell Sensitization to Helminthic Infection Develops In Utero in Humans

Human neonates are generally deficient in their ability to generate humoral immunity. This deficiency is thought to reflect physiologic immaturity of T and B cell function and lack of previous exposure to exogenous Ags. To determine whether neonatal humoral immunity can be modified by maternal helminth infection during pregnancy, we assessed Ig production by cord blood lymphocytes from healthy newborns of mothers living in an area of Kenya where schistosomiasis, bancroftian filariasis, and geohelminth infections are endemic. Twelve of 40 and 17 of 39 cord blood lymphocyte preparations from healthy newborns in Coast Province, Kenya, spontaneously made polyclonal IgE (range, 0.15–21 ng/ml) and IgG (1.6–10.1 ng/ml) in vitro. In vitro IgE synthesis by cord blood lymphocytes (CBL) was, on the average, 10-fold less than that of PBMC of Kenyan mothers (1.1–98 ng/ml) and was undetectable for CBL from newborns delivered in the United States. Schistosome and filarial Ags stimulated a 3- to &gt;100-fold increase in the production of polyclonal IgE and parasite-specific IgG Abs by lymphocytes from 10 of 40 and 6 of 39 Kenyan newborns, respectively. CBL observed to have helminth Ag-driven B cell responses were more likely to be from newborns of schistosome- or filaria-infected mothers than from uninfected mothers (p &lt; 0.05). These data indicate that the human fetus can be sensitized in utero to produce helminth-specific B cells and that neonatal B cells are intrinsically capable of IgE and IgG production.

Differential Cytotoxicity of Cord Blood and Bone Marrow–Derived Natural Killer Cells

Allogeneic cord blood is now being widely used as a source of stem cells for hematologic reconstitution after myeloablative therapy, with reported significantly lower levels of graft-versus-host disease (GVHD) compared with the use of allogeneic bone marrow (BM). This study was undertaken to investigate biologic aspects of natural killer (NK) cell activity, as recognized effector cells of the GVHD and graft-versus-leukemia (GVL) response, from cord blood and conventional BM. NK-cell activity levels of freshly isolated cells from cord blood and BM against K562 targets were comparable. Lymphokine activated killer (LAK) cells from both hematopoietic cell sources were compared for their ability to kill target cells by necrotic or apoptotic mechanisms using specific target cell lines. Cord blood cells had significantly higher necrosis-mediated cytotoxic activity against Daudi target cells compared with BM-derived cells. Cord blood LAK cells had relatively high levels of apoptotic-mediated cytotoxicity against YAC-1 target cells, whereas BM-derived LAK cells were unable to induce apoptosis in these cells. Interleukin-2 (IL-2) induced significant granzyme B activity in cord cells in contrast to BM cells, in which very little activity was measured. Western blotting confirmed these findings, with IL-2 inducing granzyme B protein expression in cord cells but not detectable levels in BM cells. BM cells had significantly lower cell surface expression of IL-2R and prolonged culture in IL-2 was only partially able to restore their deficient apoptotic cytotoxic activity. Thus, major differences exist between cord blood-derived and BM-derived mononuclear cells with respect to their NK-cell–associated cytotoxic behavior. This could have important implications for stem cell transplantation phenomena, because it suggests that cord blood may have increased potential for a GVL effect.

Differential Cytotoxicity of Cord Blood and Bone Marrow–Derived Natural Killer Cells

Allogeneic cord blood is now being widely used as a source of stem cells for hematologic reconstitution after myeloablative therapy, with reported significantly lower levels of graft-versus-host disease (GVHD) compared with the use of allogeneic bone marrow (BM). This study was undertaken to investigate biologic aspects of natural killer (NK) cell activity, as recognized effector cells of the GVHD and graft-versus-leukemia (GVL) response, from cord blood and conventional BM. NK-cell activity levels of freshly isolated cells from cord blood and BM against K562 targets were comparable. Lymphokine activated killer (LAK) cells from both hematopoietic cell sources were compared for their ability to kill target cells by necrotic or apoptotic mechanisms using specific target cell lines. Cord blood cells had significantly higher necrosis-mediated cytotoxic activity against Daudi target cells compared with BM-derived cells. Cord blood LAK cells had relatively high levels of apoptotic-mediated cytotoxicity against YAC-1 target cells, whereas BM-derived LAK cells were unable to induce apoptosis in these cells. Interleukin-2 (IL-2) induced significant granzyme B activity in cord cells in contrast to BM cells, in which very little activity was measured. Western blotting confirmed these findings, with IL-2 inducing granzyme B protein expression in cord cells but not detectable levels in BM cells. BM cells had significantly lower cell surface expression of IL-2R and prolonged culture in IL-2 was only partially able to restore their deficient apoptotic cytotoxic activity. Thus, major differences exist between cord blood-derived and BM-derived mononuclear cells with respect to their NK-cell–associated cytotoxic behavior. This could have important implications for stem cell transplantation phenomena, because it suggests that cord blood may have increased potential for a GVL effect.

Umbilical cord blood lacks circulating B lymphocytes expressing surface IgG or IgA

In vitro umbilical cord blood B lymphocytes fail to form IgG and IgA secreting plasma cells when stimulated with Pokeweed mitogen. Since previous investigators have found percentages of B lymphocytes expressing surface IgG or surface IgA comparable to those seen in adults, this implies a defect in umbilical cord blood B-lymphocyte function. We have examined surface Ig expression on umbilical cord blood B lymphocytes by flow cytometry under conditions in which serum derived Ig are rigorously excluded. Under these conditions no B lymphocytes expressing surface IgG or IgA, which should serve as precursors for IgG and IgA secreting plasma cells, were observed. This finding was confirmed by comparing the ratio of mRNA levels for immunoglobulin gamma-chain to mu-chain in mononuclear cells by quantitative mRNA-based PCR. The ratio in umbilical cord mononuclear cells was 10-fold less than that seen in adult cells. The inability of newborn peripheral blood to form IgG and IgA plasma cells may result from an absence of appropriate precursor cells and not a defect in B lymphocyte maturation.

Oral IgA-IgG treatment of chronic non-specific diarrhoea in infants and children

The effect of orally administered immunoglobulin (IgAbulin) on chronic non-specific diarrhoea of infancy was studied in seven children, median age 26 (21-36) months and duration of diarrhoea 32 (18-84) weeks. Routine laboratory tests for malabsorption and small bowel biopsies were taken in all children before and after 3 weeks of IgAbulin treatment. The biopsy specimens were analysed with regard to histopathology, electronmicroscopy, immunohistochemistry and microbiology. The number of stools decreased from a median of 4.0 (3.0-5.0) to 1.5 (1.0 3.5) (p < 0.05) stools per day over the study period.

In vitro cytokine production and phenotype expression by blood mononuclear cells from umbilical cords, children and adults

Age related differences in immunological reactions include variations in the in vitro functions of blood mononuclear cells (MNC). In an attempt to understand the mechanism behind these differences we examined age related differences in the phenotype profiles of MNC in parallel with the in vitro production of interleukin IL-6, tumour necrosis factor alpha (TNF alpha) and interferon gamma (IFNg) in neonates, children and adults. In cultures without added polyclonal activators IL-6 and TNF alpha levels in children were 3-6 times higher than those of umbilical cords and adults. However, using optimal in vitro stimulation (E. coli lipopolysaccharide (LPS), phytohaemmagglutinin or pokeweed mitogen (PWM)) no significant differences in the levels of these cytokines were observed. The levels of IFNg in PWM driven cultures followed a different pattern with comparable levels in children and adults, and unmeasurable levels in cord blood MNC. Flow cytometry analysis of the phenotypic distribution of MNC revealed age related differences in the expression of CD3, CD4, CD8, CD14, CD19, CD45RA, CD45R0, CD2, LFA-1, ICAM-1 and LFA-3. Correlation studies did not indicate that the observed differences in cytokine production could be ascribed to differences in the frequency of monocytes, T cells or B cells. The TNF alpha levels in suboptimally stimulated cultures correlated negatively with the expression of LFA-3 and positively with CD45RA, while IFNg correlated positively with CD2, LFA-1, CD45R0 and CD8. In conclusion, the study provides evidence of age related differences in the production of TNF alpha, IL-6 and IFNg among neonates, children and adults. These differences may to some extent be caused by differences in the expression of cell surface molecules involved in cellular interactions and signalling.

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.

Mycobacterial infections: are the observed enigmas and paradoxes explained by immunosuppression and immunodeficiency?

The enigmas and paradoxes observed in tuberculous patients, in Bacille Calmette-Guérin-vaccinated people and in Bacille Calmette-Guérin-treated cancer patients have been examined, in an attempt to explain them through the mechanisms of immunodeficiency and immunosuppression. A dual effect is postulated: an immunosuppression induced by the infecting mycobacteria that adds to a pre-existing or emerging state of immunodeficiency of the infected individual. The immunological cellular and humoral anergies observed at the beginning of a tuberculous therapy are usually lifted after the first two weeks of treatment. This restoration of immune responsiveness may be attributed to the destruction or to the growth inhibition of immunosuppressive mycobacteria. The observation that drugs cytocidal in vitro do not always sterilize the patients under treatment whereas bacteriostatic drugs do, may find an explanation in the dual immunosuppression induced by cytocidal drugs and mycobacteria. The fact that Bacille Calmette-Guérin applied as an immunotherapy to residual cancer has either a favorable or an unfavorable action may be due to the immunosuppressive activity attached to some Bacille Calmette-Guérin strains and to some cancers. The variable protective activity of Bacille Calmette-Guérin vaccines may be due to the immunological status of the vaccinated people and the compositional differences between strains. The protective activity of subunit vaccines in experimental models can be attributed to the elimination of immunosuppressive factors present in whole killed mycobacteria.

Delineation of producing ability of IgG and IgA subclasses by naive B cells in newborn infants and adult individuals

Neonatal B cells with the naive (sIgD+) phenotype are able to generate IgG- and IgA-producing cells as well as IgM production in the presence of memory CD4+ T cells expressing L-selectin (CD62L) in pokeweed mitogen-stimulated cultures. We used this system to examine comparatively the ability of naive B cells to produce IgG and IgA subclasses in newborn infants and adult individuals. Naive B cells were enriched from both donors on the basis of sIgD positivity, and memory (CD45RO+) CD4+ T cells with CD62L expression were isolated from adults. We here demonstrate some differences in profiles of IgG and IgA subclass production between neonatal and adult naive B cells. In neonatal B cells, IgG1 and IgG3 were predominantly produced, but IgG2 and IgG4 production was virtually absent. Similar to neonatal B cells, adult naive B cells produced mainly IgG1 and IgG3, although memory (sIgD-) B cells from adults secreted all of the IgG subclasses. It should be noted that low but detectable levels of IgG2 and IgG4 were found in adults' naive B cell cultures. Although IgA produced by neonatal B cells was exclusively IgA1, IgA2-secreting cells were identifiable in adult naive B cells. The results suggest that further class switch of naive B cells to IgG2, IgG4 and IgA2 in addition to IgG1 and IgG3 may be controlled by their own age-dependent maturation process.

Immune status of newborns in perinatal chlamydial infection

PROBLEM

Thirty newborns, delivered by mothers with urogenital chlamydiosis, diagnosed on the 35th-36th weeks of gestation, and 10 newborns of healthy mothers were studied immunologically. CD3 (T-lymphocytes), CD19 (B-lymphocytes), CD4 (T-helpers-inductors), CD8 (T-suppressor-cytotoxic), T-lymphocyte response to PHA, levels of Ig G, A, M in umbilical blood were detected.

METHOD

Chlamydia trachomatis antibody's titers in umbilical blood were determined by indirect immunofluorescent method (with antigen C. trachomatis, serovar L2). Antibody titers found in umbilical blood were in 50% of cases higher than antibody level in mother's blood serum, and they later varied from 1:64 to 1:256. It was established that newborns delivered by mothers with urogenital chlamydiosis had imbalance of T-lymphocyte subsets, decrease in the numbers of T- and B- lymphocytes, and increased level of Ig M, while the level of Ig G did not change significantly. The exposed disproportion in immune status neonatal, born from mothers with urogenital chlamydiosis, in combination with high C. trachomatis antibody titers in umbilical blood may be prognostic of the development of neonatal chlamydial infections.

Relationships between maternal malaria and malarial immune responses in mothers and neonates

Immune responses of 97 Gambian women and their neonates were studied. New methods distinguished between active and previous placental malaria, were used to examine relationships between maternal malaria and neonatal immune responses. Many placentas (61%) had active or previous malarial infection. Maternal and cord malarial IgG levels correlated (P < 0.001). Malarial IgG was raised in cord blood in active placental malaria; IgM was not detected. Mean lymphoproliferation and the proportion of responders to soluble P. falciparum antigens (F32) and conserved regions of p190 expressed on trophozoites and schizonts (190L and 190N) were higher in neonates than mothers. There was no clear relationship between maternal malaria and neonatal mean lymphoproliferation to malarial antigens, although fewer neonates responded when mothers were actively infected. Matched maternal and neonatal lymphoproliferation responses did not correlate. However, first born neonatal lymphoproliferation to PPD and malarial antigens appeared lower than other neonates, in agreement with lower lymphoproliferation in primigravidae compared with multigravidae. Also in common with mothers, autologous plasma suppressed neonatal lymphoproliferation to PPD and malarial antigens, suggesting common immunoregulation. Higher cortisol or other circulating factors in first pregnancies may be implicated. The relevance of cell-mediated malarial immune responses detected at birth remains to be established.

BY55 monoclonal antibody delineates within human cord blood and bone marrow lymphocytes distinct cell subsets mediating cytotoxic activity

We had previously reported, using BY55 monoclonal antibody, a cell surface 80-kDa protein restricted to human functional peripheral blood cytotoxic lymphocytes with either natural killer CD3- or cytotoxic T lymphocyte CD3+CD8+ phenotype. In the present report, we studied the cytotoxic lymphocytes in adult bone marrow and newborn cord blood as these organs are commonly used as sources of hematological stem cells for allogeneic transplantation. Our results showed that BY55 mAb labeled only 5-10% of the bone marrow lymphocytes, which included a major proportion of CD3+ CD8+ cytotoxic T lymphocytes. Interestingly, within cord blood cells, BY55+ lymphocytes represented 20-35% of the lymphocytes corresponding exclusively to a CD3- cell subset. Furthermore, we detected in cord blood no cytotoxic T lymphocyte activity but we demonstrated that the CD3-BY55+ cell subset contained the whole natural killer activity.

Relative immunocompetence of the newborn harbour seal, Phoca vitulina

The immune system of many mammalian species is not fully developed at birth, with newborns obtaining temporary immunological protection from maternal antibodies. Little is known of the immune system of the harbour seal, and developmental aspects of its immune system have not been systematically studied. We collected blood and milk samples from nine free-ranging mother-pup pairs throughout the lactation period on Sable Island, Canada, in an effort to characterise developmental aspects of the immune system of this newborn pinniped. Pup lymphocytes responded stronger to the mitogens concanavalin A, phytohaemagglutinin, and pokeweed mitogen than the lymphocytes of their mothers. In contrast to newborn cats and dogs, newborn seal pups developed high specific antibody responses after immunisation with an inactivated rabies vaccine. Circulating levels of total IgG in newborn pups were low (3% of maternal levels), but increased rapidly after colostrum intake (to 65% of maternal levels after 15 days). A similar pattern of increase in pup serum was observed for phocine distemper virus specific antibodies which had been detected in the serum and milk of mothers, suggesting that the transfer of colostral antibodies is an important feature of temporary protection for the pup. We speculate that the relative immunocompetence of the harbour seal at birth reflects an adaptation to its relatively short nursing period and limited maternal care.

New concepts of allergy to cow's milk

CMA is a diagnostic and therapeutic problem in the field of pediatrics. The response to oral cow's milk challenge was evaluated in patients with suspective CMA. To investigate immune mechanisms in different subtypes of CMA, suppressor activity, in vitro IFN-gamma and IL-4 generation, eosinophil activation and humoral immune response were measured. Also, changes in the function of the immune system were evaluated when patients had clinically recovered from CMA. The results of different measurements were correlated with the patients' clinical response to cow's milk challenge. The prechallenge suppressor activity was found to be low in patients with challenge-proven CMA when compared with those clinically negative to oral cow's milk challenge but had normalized after a 4-18 month milk-elimination period in patients who had recovered from CMA. IFN-gamma generation was low in patients with active CMA but had clearly enhanced in patients recovering from CMA. The serum concentration of ECP increased significantly during oral cow's milk challenge in patients with cutaneously manifested CMA. Measured by the ELISPOT method, the patients with active CMA mounted a high, non-antigen-specific immune response but were unable to direct the antigen-specific response, especially in the IgA class. After a follow-up of a mean 13.5 months on cow's milk elimination diet, the immune response to cow's milk antigens had developed in patients who had recovered from CMA. The development in the capacity to mount an adequate immune response to specific protein antigens, especially in the IgA class, can be interpreted as deriving from the development in T-lymphocyte regulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Immune activation during infancy in healthy humans

Immune activity during infancy was investigated using blood samples from 30 neonates and 52 healthy infants between 2 and 15 months of age attending for immunization. The purpose of this study was to assess the total immune activity of T cells using soluble interleukin-2 receptor (IL-2R) and interferon-gamma concentrations. These were compared with the proportion of CD4 CD45RO-, IL-2R (CD25)-, and transferrin receptor (CD71)-positive peripheral blood lymphocytes. The median duration of breast-feeding and of introduction of solid feeds was 4.2 and 4.0 months, respectively. Compared to neonates, the mean +/- SE soluble IL-2R concentration peaked at 4 months of age (1670 +/- 94 vs 3060 +/- 252 U/ml; P < 0.0001), as did pooled interferon-gamma levels. The percentage of CD4 CD45RO T cells remained low and the proportion of activated peripheral blood lymphocytes decreased during infancy. We conclude that noncirculatory immune activity is increased during infancy and this is associated with weaning.

Increased cyclosporine sensitivity of T cells from cord blood compared with those from the adult

Despite the increasing numbers of paediatric transplants performed, little is known about the immune responses of T lymphocytes in human neonates. Here we have compared the effects of cyclosporine on the phytohaemagglutinin (PHA) response of immature (cord) and mature (adult) lymphocytes using the following parameters of activation: (i) proliferation, measured by 3H-thymidine uptake; (ii) expression of cell surface IL-2 receptor; (iii) release of IL-2 into the supernatant. Cyclosporine was added to cultures of PHA-stimulated lymphocytes at doses ranging from 5 to 5000 ng/ml. The proliferative response of cord lymphocytes was considerably more sensitive to cyclosporine at each dose, so that 50% inhibition was achieved by 6 ng/ml and 21.5 ng/ml doses of cyclosporine on cord and adult lymphocytes, respectively. Expression of the IL-2 receptor by PHA-activated T cells and their subsets was assessed by flow cytometry. Cyclosporine inhibited IL-2 receptor expression to a significantly greater degree in cord CD4 and CD8 cells (49.7% and 70.1%) than in adults (17.9% and 30.0%). Biologically active IL-2 release was measured using the IL-2-dependent cell line CTLL-2. Cyclosporine at doses 50-5000 ng/ml produced 80-99% inhibition of both cord and adult responses. However, at very low doses (5 ng/ml) cyclosporine produced 69.3% inhibition of cord lymphocytes, compared with 42.0% of adult lymphocytes. These results suggest that the T cells of neonates are considerably more sensitive to cyclosporine than are adult T cells.

Maternal infections influence infection susceptibility in childhood

The proposed hypothesis suggests that the types of infections commonly experienced in pregnancy and in childhood are linked. The suggestion is made that maternal infections leave an impression on the developing fetal immune system and modulate future responsiveness to infection and/or vaccination challenge. A number of factors are explored which may influence this process, namely immunoregulation in pregnancy and infection type, gestation, maturity of the fetal immune system, and parity.

Ontogeny of anti-human immunodeficiency virus (HIV) antibody production in HIV-1-infected infants

The early serologic response of infants to infection with human immunodeficiency virus type 1 (HIV-1) is normally obscured by the presence of transplacentally acquired maternal HIV antibody. By measuring HIV antibody produced in vitro by lymphocytes isolated from peripheral blood of infants and children of HIV-1-infected mothers, we have been able to study the natural acquisition of humoral immunity to perinatal HIV-1 infection. One hundred ninety-seven infants of HIV-1-infected women were studied prospectively and longitudinally from birth. In the neonatal period, infected infants produced only small amounts of HIV-specific IgG antibodies to a restricted number of antigens. The amount of immunoglobulin to HIV-1 and the number of HIV-1 antigens recognized increased with age. After 6 months of life 85% of infected infants made detectable antibody to two or more viral proteins. Antibody to gp160 appeared first and was the most frequently found at all ages, followed by antibody to the envelope proteins gp120 and gp41. The amount of HIV antibody produced correlated positively with the percentage of CD4+ T lymphocytes in peripheral blood. This assay provides a method of studying the immunogenicity of vaccines against HIV-1 in HIV-1-infected infants and of assessing the effect of early therapeutic interventions on the humoral response to HIV-1.

In vitro stimulation of human fetal lymphocytes by mitogens and interleukins

Human lymphocytes derived from fetal spleen and liver were studied for their capacity to respond to mitogens and interleukins using different in vitro models (cell volume increase, [3H]thymidine incorporation, Ig secretion). Although the number of mature B and T cells in the fetal liver preparations remained nearly constant [Settmacher et al. (1991) Immunobiol. 182, 256], only lymphocytes obtained from fetal organisms before the 25th week of gestation could respond to some of the polyclonal stimulators (PWM, anti-CD3 + IL-2, SAC + IL-2, SAC + IL-4) tested, whereas cells obtained after that period failed. In the fetal spleen, however, with increasing percentages of mature B and T cells during fetal development, a growing ability to respond to mitogens was registered, which, however, did not achieve the values found for the adult spleen material.

Fetal mononuclear cells show a comparable capacity with maternal mononuclear cells to produce IL-8 in response to lipopolysaccharide in chorioamnionitis

IL-8 is a chemotactic and activating cytokine for neutrophils which eliminate invading bacteria by releasing bactericidal metabolites. Cord blood mononuclear cells (CBMCs) obtained from neonates born to mothers with chorioamnionitis actively produced a significantly higher amount of IL-8 than those of neonates without chorioamnionitis, suggesting that the mononuclear cells of fetuses with chorioamnionitis had been activated in utero. As lipopolysaccharide (LPS) can often be detected in the uteroplacental space in chorioamnionitis, the LPS-mediated activation mechanism of neonatal mononuclear cells was analyzed in vitro to produce IL-8. Neonatal mononuclear cells stimulated with LPS increased IL-8 production in a time- and dose-dependent manner. The ability of term or preterm neonatal mononuclear cells to produce IL-8 was comparable with that of adult (maternal) mononuclear cells, suggesting functional maturity of the neonatal or fetal mononuclear cells to produce IL-8. However, IL-8 production by neonatal CBMCs was down-regulated by dexamethasone, a glucocorticoid which is clinically administered to mothers to promote fetal lung maturity in preterm delivery. Our present study revealed a regulatory mechanism of fetal IL-8 production, suggesting that functionally mature fetal mononuclear cells produce IL-8 in response to LPS in chorioamnionitis and activate the fetal defense mechanism against infection.

A study of interferon-gamma and interleukin-2 production in premature neonates and neonates with intrauterine growth retardation

Mononuclear cells from aborted fetuses, preterm infants, intrauterine growth retardation (IUGR) fetuses, and mature infants were stimulated with OK432 and PHA to study their effect on the production of interferon gamma (IFN-gamma) and interleukin-2 (IL-2), respectively. IFN-gamma production was reduced in the mature delivery group, while its production in preterm delivery and IUGR groups was markedly reduced compared to those in adults and the mature delivery group. Reduced IFN-gamma production in preterm delivery and IUGR groups was attributable neither to a decrease in T-cells nor to enhanced sensitivity of T-cells to prostaglandins. Unlike IFN-gamma production, IL-2 production in preterm delivery groups was higher than that in adults; its production in the IUGR group was comparable to that in adults. In addition, both IFN-gamma and IL-2 production in premature delivery cases was enhanced when these cases were exposed to the stress of infection.

Two different maturational stages of natural killer lymphocytes in human newborn infants

The objective of this study was to assess the basis for the diminished natural killer (NK) lymphocyte activity of neonates. We found either severely reduced (63% of 68 neonates) or normal (similar to healthy adult) levels of NK activity. The percentages of cord blood mononuclear cells from the two groups of infants that expressed CD16, a differentiation antigen found in NK cells, were similar and within the range found in peripheral blood mononuclear cells of adults. However, infants with low NK activity had reduced numbers of cells in the CD16+56+ subpopulation, whereas the number of these effector cells present in cord blood mononuclear cells from infants with normal NK activity was within the range found in adults. Recombinant interleukin-2, but not recombinant interferon-gamma, normalized the low NK activity of infants in a dose- and time-dependent manner. Analysis of the pattern of target cell susceptibility to lysis, together with the CD16+CD3- phenotype of the precursor and effector lymphocytes, demonstrated that the induced cytotoxicity was mediated by NK cells. In contrast, NK cells from infants with normal cytotoxic levels exhibited a functional response to interleukin-2 and interferon-gamma similar to that of adults. Our results indicate that NK cells in human neonates go through two different maturational stages.

Enumeration of human peripheral blood lymphocytes secreting immunoglobulins of major classes and subclasses in healthy children and adults

The reverse enzyme-linked immunospot assay was modified to enumerate peripheral blood mononuclear cells (PBMC) secreting IgG1-4, IgA1-2, and IgM. Anti-human IgG F(ab')2 and mouse monoclonal antibodies specific to each of the isotypes were used as solid-phase capture antibodies and developing antibodies, respectively. Although attempts were also made to detect IgD- and IgE-secreting cells (SC), their numbers in the peripheral blood were too few to be reliably estimated. The assay was applied to study healthy subjects including 21 neonates within 3 days of birth, 44 1- to 48-month-old children, and 32 adults. Sixty percent of these neonates had IgM SC in small numbers (less than 20 per 10(6) PBMC), but only three neonates had IgSC of other isotypes. In contrast, by 1-2 months of age children had IgSC of all isotypes, including IgA2 and IgG4, often in higher numbers than adults. The relative frequencies of IgSC were IgA1 greater than IgG1 greater than IgM greater than IgG2 greater than IgG3 greater than IgG4 greater than IgA2 in the children and IgA1 greater than IgG1 greater than IgA2 greater than IgM greater than IgG4 greater than IgG2 greater than IgG3 in the adults. The order of the serum concentrations in the adults was IgG1 greater than IgG2 greater than IgA greater than IgM greater than IgG4 greater than IgG3. No correlation was found between the serum level and the IgSC number of individual isotypes (except for serum IgA and IgA1-SC). This new methodology should facilitate investigating the current status of immunoglobulin synthesis and the Ig repertoire in adults and children, in health and in disease.