The ontogeny of T lymphocyte maturation and function

Pro-inflammatory cytokine ratios determine the clinical course of febrile neutropenia in children receiving chemotherapy

Background

Febrile neutropenia is a common and serious complication during treatment of childhood cancer. Empirical broad-spectrum antibiotics are usually administered until neutrophil cell count recovery. It was the aim of this study to investigate cytokine profiles as potential biomarkers using in-vitro sepsis models to differentiate between distinct clinical courses of febrile neutropenia (FN).

Methods

We conducted an observational study in FN episodes of pediatric oncology patients. Courses of neutropenia were defined as severe in case of proven blood stream infection or clinical evidence of complicated infection. We collected blood samples at various time points from the onset of FN and stimulated ex vivo with lipopolysaccharide (LPS) and Staphylococcus epidermidis (SE) for 24 h. Twenty-seven cytokine levels were measured in the whole blood culture supernatants by a multiplex immunoassay system.

Results

Forty-seven FN episodes from 33 children were investigated. IL-8, IL-1β, and MCP-1 expression increased significantly over time. IL-8, MIP-1α, MIP-1β, MCP-1, and TNF-α showed significantly lower concentration in patients with a clinically severe course of the FN.

Conclusions

Distinct patterns of cytokine profiles seem to be able to determine infectious FN and to predict the severity of its clinical course. If these data can be verified in a multi-centre setting, this may finally lead to an individualized treatment strategy facilitating antibiotic stewardship in these patients.

Pharmacokinetics and Clinical Pharmacology of Monoclonal Antibodies in Pediatric Patients

Monoclonal antibodies (mAbs) and their derivatives are increasingly used in pediatric pharmacotherapy, and the number of antibody-based drug products with approved pediatric indications is continuously growing. In most instances, pediatric use is being pursued after the efficacy and safety of novel antibody medications have been established in adult indications. The pediatric extrapolation exercise that is frequently used in this context to bridge efficacy and safety from adults to children is oftentimes challenged through uncertainties and knowledge gaps in how to reliably extrapolate pharmacokinetics and clinical pharmacology of mAbs to different pediatric age groups, and how to derive age-appropriate dosing regimens that strike a balance between precision dosing and practicability. The article highlights some of the pharmacokinetic and clinical pharmacology challenges with regard to therapeutic use of mAbs and antibody derivatives in children, including immunogenicity events. Although considering body size-based differences in drug disposition can account for many of the perceived and actual differences in the distribution and elimination of antibody-based therapeutics between children and adults, increasing evidence suggests potential or actual age-associated differences beyond size differences, especially for young pediatric patients such as newborns and infants. To overcome age-associated differences in antibody disposition, various different dosing approaches have been applied to ensure safe and efficacious antibody exposure for pediatric populations of different ages. The development of such dosing regimens and the associated pathway to pediatric indication approval is illustrated in more detail for two antibody-based biologics, the fusion protein abatacept and the mAb tocilizumab.

Induction of IL-10 cytokine and the suppression of T cell proliferation by specific peptides from red cell band 3 and in vivo effects of these peptides on autoimmune hemolytic anemia in NZB mice

PURPOSE

The anion channel protein band 3 is the main target of the pathogenic red blood cells (RBC) autoantibodies in New Zealand black (NZB) mice. CD4 T cells from NZB mice with autoimmune hemolytic anemia respond to band 3. Previously, we have shown that IL-10 and peptides containing a dominant T cell epitope from red cell band 3 modulate autoimmune hemolytic anemia in NZB mice. Because of the immunoregulatory role of IL-10 in autoimmune diseases, we aim to identify individual band 3 peptides that induce high IL-10 production and simultaneously suppress CD4 T cell proliferation and to investigate the effect intranasal administration of IL-10 producing band 3 peptides on autoantibody responses of NZB mice.

METHODS

Splenic CD4 T cells of NZB mice were isolated and stimulated by co-culture of T cells with individual band 3 peptides. IL-10 production was measured by enzyme-linked immunosorbent assay and proliferative response of CD4 T cells was estimated by incorporation of [³H] thymidine assay. NZB mice were given either PBS, or peptides 25 (241-251) and 29 (282-296) or both peptides intranasally on three occasions at 2-day intervals. The mice were bled at 6, 10 and 18 weeks after peptide inhalation, and the number of RBC auto-antibodies was measured by DELAT and hematocrit values were assessed.

RESULTS

Peptides 25 (241-251) and 29 (282-296) induced the highest IL-10 production by CD4 T cells. These peptides also inhibited the peak T cell proliferative response. 6 and 10 weeks after peptide inhalation, the total IgG, IgG1 and IgG2a in mice treated with both peptides 241-251 and 282-296 were significantly higher than control (P < 0.05). However, no significant difference in the mean hematocrit between of the peptide-treated mice and the control group was found.

CONCLUSIONS

Although band 3 peptides 241-251 and 282-296 induced to the highest IL-10 production by CD4 T cells in vitro but fail to reverse the RBC autoantibody response in vivo. Modifications to improve solubility these peptides might help to modulate the immune response toward a T helper-2 profile and decrease the severity of anemia.

T-Cells Underlie Some but Not All of the Cerebellar Pathology in a Neonatal Rat Model of Congenital Lymphocytic Choriomeningitis Virus Infection

Lymphocytic choriomeningitis virus (LCMV) infection during pregnancy injures the human fetal brain. Neonatal rats inoculated with LCMV are an excellent model of congenital LCMV infection because they develop cerebellar injuries similar to those in humans. To evaluate the role of T-lymphocytes in LCMV-induced cerebellar pathology, congenitally athymic rats, deficient in T-lymphocytes were compared with euthymic rats. Peak viral titers and cellular targets of infection were similar, but viral clearance from astrocytes was impaired in the athymic rats. Cytokines and chemokines rose to higher levels and for a greater duration in the euthymic rats than in their athymic counterparts. The euthymic rats developed an intense lymphocytic infiltration, accompanied by destructive lesions of the cerebellum and a neuronal migration defect because of T-cell-mediated alteration of Bergmann glia. These pathologic changes were absent in the athymic rats but were restored by adoptive transfer of lymphocytes. Athymic rats were not free of pathologic effects, however, as the virus induced cerebellar hypoplasia. Thus, T-lymphocytes play key roles in LCMV clearance, cytokine/chemokine responses, and pathogenesis of destructive lesions and neuronal migration disturbances but not all pathology is T-lymphocyte-dependent. Cerebellar hypoplasia from LCMV occurs even in the absence of T-lymphocytes and is likely due to the viral infection itself.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Cytokine responses correlate differentially with age in infancy and early childhood

The functional differentiation of immune cells at early age plays a central role in immune physiology, e.g. for the sufficient eradication of pathogens. However, imbalances in effector cell responses may also have an impact in the pathophysiology of childhood diseases such as atopy and autoimmune disorders. As information on immune cell responses in infancy and early childhood is scarce, we conducted an observational, cross-sectional study in healthy newborns (n = 18), infants and young children (n = 54) aged 1-96 months and adult controls (n = 19) to assess cytokine mRNA and protein expression upon phorbol 12-myristate 13-actate/ionomycin stimulation and LPS-induced IL-12 expression in monocytes. The intracellular expression of interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha (R = 0.748, P < 0.0001; R = 0.784, P < 0.0001, respectively) and interleukin (IL)-2 protein expression (R = 0.384, P = 0.008) was demonstrated to increase progressively with age. While a correlation between IL-4 protein expression and age was noted (R = 0.342, P = 0.007), the levels of IL-5 and IL-10 protein expression tended to be regulated on an individual basis during infancy and early childhood. An age correlation was also observed for intracellular IL-12 expression (R = 0.331, P = 0.009) in monocytes. These findings are valuable for further assessment of normal variations and maturation processes in immune cell responses and for the clinical-therapeutic monitoring of immunological status in various childhood diseases.

Perinatal transmission and viral evolution of hepatitis C virus quasispecies in infants coinfected with HIV

OBJECTIVES

Three HIV/hepatitis C virus (HCV)-coinfected children and the mothers of 2 were studied to examine the nature of perinatal HCV infection in HIV-coinfected infants and to assess the evolution of viral quasispecies thereafter. Sequences of the hypervariable region in the N terminus of the E2/NS1 region (HVR-1) of the children and their mothers were compared. HCV quasispecies changes in the infants were tracked over several years.

METHODS

Sequence similarity comparisons and phylogenetic trees were derived from cDNA of plasma isolates. Quantitation of plasma HCV and HIV was performed in the children, as well as CD4 T-cell percentage and liver transaminases.

RESULTS

Phylogenetic analysis of the mother-child pairs suggested that transmission of multiple dominant and nondominant variants identified in the mother were seen. HCV diversification in the children was seen as early as 2 months of life. The child with the best immune status and HIV control demonstrated the most diversification throughout.

CONCLUSION

Multiples HCV variants transmitted from mother to child and their early changes in the child may be related to maternal antibody. Variation after the 1st year of life may reflect immunologic pressure from the child. There was no trend suggesting that the presence or absence of selective immunologic pressure affected HCV load or liver transaminase values.

Mechanisms of the natural reactivity of lymphocytes from noninfected individuals to membrane-associated Leishmania infantum antigens

Membrane-associated Leishmania Ags (MLA) or soluble Leishmania Ags were used in vitro to stimulate cord blood or PBMC from healthy donors noninfected by Leishmania parasites. MLA, but not soluble Leishmania Ags, constantly induce strong proliferation of cord blood mononuclear cells and PBMC from noninfected individuals. Responding cells are CD3+, CD4+, TCRalphabeta+, CD45RO+, and CD45RA+ and secrete IFN-gamma and IL-10, but not IL-4. MLA do not activate NK cells nor NKT cells. Membrane Ags also induce purified macrophages from noninfected individuals to secrete IL-10 and TNF-alpha, but have no effect on IL-1alpha or IL-12 secretion. The effects of MLA are proteinase K-sensitive and resistant to lipid extraction. The lymphoproliferative responses are inhibited by anti-HLA-DR Abs and require Ag processing by APCs, excluding that the biological effect of MLA could be attributed to a superantigen. Finally, TCR repertoire analysis shows that the T cell expansion induced by MLA uses TCR with various variable beta segment rearrangements and CDR3 lengths, features much more characteristic to those observed with a polyclonal activator than with a conventional Ag. These results suggest a particular mechanism developed during the host's natural response to Leishmania parasites that allows direct activation of naive CD4 lymphocytes by parasite membrane-associated Ags.

Cytomegalovirus infection and development of allergic diseases in early childhood: interaction with EBV infection?

BACKGROUND

Chronic replication of cytomegalovirus and EBV in early life may affect the immune system and play a role in the development of allergy in children.

OBJECTIVE

To assess the relation between cytomegalovirus infection and allergic disorders in children, including a possible interaction with EBV infection.

METHODS

From a prospective birth cohort study in Stockholm, on factors of importance for development of allergy, 2581 four-year-old children were enrolled. The classification of allergic diseases was based on questionnaire answers and determination of IgE antibodies to common airborne and food allergens. IgG to cytomegalovirus was determined by a commercial ELISA and to EBV by indirect immunofluorescence.

RESULTS

A total of 1191 (46%) children were cytomegalovirus-seropositive. There were no significant associations between seropositivity to cytomegalovirus and allergic manifestations, such as bronchial asthma, suspected allergic rhinitis, or atopic dermatitis. Seropositivity to cytomegalovirus alone, ie, without seropositivity to EBV, was related to IgE antibodies to airborne and food allergens (adjusted odds ratio, 1.8; 95% CI, 1.2-2.9). An antagonism between cytomegalovirus and EBV in relation to sensitization to airborne and food allergens was suggested ( P = .05).

CONCLUSION

The study does not support the hypothesis that previous cytomegalovirus infection plays an important role in the pathogenesis of bronchial asthma, suspected allergic rhinitis, or atopic dermatitis in children. However, in the absence of EBV infection, cytomegalovirus infection may be related to sensitization to airborne and food allergens.

Bordetella pertussis infection in 2-month-old infants promotes type 1 T cell responses

Neonatal immaturity of the immune system is currently believed to generally limit the induction of immune responses to vaccine Ags and to skew them toward type 2 responses. We demonstrated here that Bordetella pertussis infection in very young infants (median, 2 mo old) as well as the first administration of whole-cell pertussis vaccine induces B. pertussis Ag-specific IFN-gamma secretion by the PBMC of these infants. IFN-gamma was secreted by both CD4(+) and CD8(+) T lymphocytes, and the levels of Ag-induced IFN-gamma secretion did not correlate with the age of the infants. Appearance of the specific Th-1 cell-mediated immunity was accompanied by a general shift of the cytokine secretion profile of these infants toward a stronger Th1 profile, as evidenced by the response to a polyclonal stimulation. We conclude that the immune system of 2-mo-old infants is developmentally mature enough to develop Th1 responses in vivo upon infection by B. pertussis or vaccination with whole-cell pertussis vaccines.

Increased Th1 and Th2 allergen-induced cytokine responses in children with atopic disease

BACKGROUND

Polyclonal cytokine responses following stimulation of T cells with mitogens or superantigens provides information on cytokine production from a wide range of T cells. Alternatively allergen-induced T cell responses can provide information on cytokine production by allergen-reactive T cells. While there is evidence of increased Th2 and reduced Th1 cytokine production following T cell stimulation with non-specific mitogens and superantigens, the evidence that Th1 cytokine production to allergens is decreased in line with a postulated imbalance in Th1/Th2 responses is unclear, with studies finding decreased, no difference or increased IFN-gamma responses to allergens in atopic subjects.

OBJECTIVE

To examine childhood polyclonal and allergen-induced cytokine responses in parallel to evaluate cytokine imbalances in childhood atopic disease.

METHODS

PBMC cytokine responses were examined in response to a polyclonal stimulus, staphylococcal superantigen (SEB), in parallel with two inhalant allergens, house dust mite (HDM) and rye grass pollen (RYE), and an ingested allergen, ovalbumin (OVA), in (a) 35 healthy children (non-atopic) and (b) 36 children with atopic disease (asthma, eczema and/or rhinitis) (atopic).

RESULTS

Atopic children had significantly reduced IFN-gamma and increased IL-4 and IL-5 but not IL13 production to SEB superantigen stimulation when compared with non-atopic children. HDM and RYE allergens stimulated significantly increased IFN-gamma, IL-5 and IL-13, while OVA stimulated significantly increased IFN-gamma production in atopic children.

CONCLUSION

We show that a polyclonal stimulus induces a reduced Th1 (IFN-gamma) and increased Th2 (IL-4 and IL-5) cytokine pattern. In contrast, the allergen-induced cytokine responses in atopic children were associated with both increased Th1 (INF-gamma) and Th2 (IL-5 and IL-13) cytokine production. The increased Th1 response to allergen is likely to reflect prior sensitization and indicates that increases in both Th1 and Th2 cytokine production to allergens exists concomitantly with a decreased Th1 response to a polyclonal stimulus in atopic children.

Ontogeny of T-helper 1 and T-helper 2 cytokine production in childhood

Compared to adults, infants and young children demonstrate differences in their immune response, indicating that there is maturation or change over time and it is probable that this may be reflected in cytokine production. Cytokine responses have been demonstrated to be different in atopic and non-atopic individuals. In this study, we examined T-helper 1 (Th1) (interferon-gamma [IFN-gamma]) and T-helper 2 (Th2) (interleukin [IL]-4, IL-5, and IL-13) cytokine release from atopic and non-atopic children in response to the staphylococcal superantigen, staphylococcal enterotoxin B (SEB). In non-atopic and atopic children, IFN-gamma, IL-4, and IL-5 release was significantly related to age. Non-atopic children younger than 2 years of age were found to have significantly reduced Th2 (IL-4, IL-5, and IL-13) responses when compared with older, non-atopic children. Atopic children had a reduced IFN-gamma response when compared with non-atopics in early childhood; however, the decreased IFN-gamma response seen in early childhood did not persist after 10 years. These age-related changes in cytokine production provide further support for the concept that cytokine deviations may determine the natural history of atopic disease during early childhood. In addition, the present study indicates the necessity of age-matched controls when examining children for both Th1 (IFN-gamma) and Th2 (IL-4) cytokine release.

Effect of cefotaxime on cytokine production in newborns and adults in vitro

The in vitro effect of cefotaxime on the production of interleukin (IL)-1beta, IL-2, IL-6 and tumor necrosis factor alpha (TNFalpha) was studied in term neonates and was compared with that of adults. The addition of cefotaxime caused a significant enhancement of IL-2 production by cells of both adults and neonates, and increased the secretion of TNFalpha by peripheral blood mononuclear cells (PBMC) of adults, whereas the synthesis of this cytokine by cord blood mononuclear cells (CBMC) of the newborns was not affected. In contrast with the described stimulatory effects of cefotaxime, this drug induced dose-dependent inhibition of the spontaneous and lipopolysaccharide (LPS)-induced IL-1beta production by cells of the two groups, but had no effect on the in vitro production of IL-6. These data suggest that cefotaxime, apart from its known antimicrobial activity, may modify the host immune response of both newborns and adults, via the alteration of cytokine production.

Immunocytochemical localization of phospholipase C isozymes in cord blood and adult T-lymphocytes

The response of T-cells to peptide antigen plus major histocompatibility complex (MHC) consists of a series of cellular events collectively called T-cell activation. An essential component of this pathway is phospholipase C (PLC)gamma1, whose hydrolytic activity increases rapidly after binding of ligands to the T-cell receptor (TCR) and consequent activation of tyrosine kinases. Recent studies also suggest a GTP binding protein-dependent activation of PLCbeta during the early steps of T-cell activation. On the basis of these findings, we first checked the expression of PLC isoforms by Western blotting and by confocal and electron microscopy techniques, and then we looked for the phosphoinositide breakdown induced by CD3 engagement in cord and adult T-lymphocytes. Our results indicated that PLCbeta1 was almost exclusively expressed in cord T-cells, whereas PLCbeta2 was more strongly represented in the adult. The amount of PLCgamma1 was found to be larger in the adult than in cord cells. No significant differences were found in PLCgamma2 and delta2 expression. PLCdelta1 was scarcely detectable. On CD3 stimulation, adult lymphocytes gave rise, as expected, to a dramatic increase in phosphoinositide breakdown, whereas in cord cells this response was scarcely detected. These results indicate that a shift in PLC expression occurs in the postnatal period and that this change is associated with induction of the capability to respond to CD3 engagement with phosphoinositide hydrolysis.

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.

Cellular immune responses to Neisseria meningitidis in children

There is an urgent need for effective vaccines against serogroup B Neisseria meningitidis. Current experimental vaccines based on the outer membrane proteins (OMPs) of this organism provide a measure of protection in older children but have been ineffective in infants. We postulated that the inability of OMP vaccines to protect infants might be due to age-dependent defects in cellular immunity. We measured proliferation and in vitro production of gamma interferon (IFN-gamma), tumor necrosis factor alpha, and interleukin-10 (IL-10) in response to meningococcal antigens by peripheral blood mononuclear cells (PBMCs) from children convalescing from meningococcal disease and from controls. After meningococcal infection, the balance of cytokine production by PBMCs from the youngest children was skewed towards a TH1 response (low IL-10/IFN-gamma ratio), while older children produced more TH2 cytokine (higher IL-10/IFN-gamma ratio). There was a trend to higher proliferative responses by PBMCs from older children. These responses were not influenced by the presence or subtype of class 1 (PorA) OMP or by the presence of class 2/3 (PorB) or class 4 OMP. Even young infants might be expected to develop adequate cellular immune responses to serogroup B N. meningitidis vaccines if a vaccine preparation can be formulated to mimic the immune stimulus of invasive disease, which may include stimulation of TH2 cytokine production.

Neonatal dendritic cells

The capacity of lymphoid dendritic cells from human cord blood or adult peripheral blood to support a mixed leukocyte reaction in cord blood and adult T cells has been compared. Cord blood dendritic cells have a limited ability to induce either adult or cord blood T cells to proliferate in response to typical concentration of phytohemagglutinin or concanavalin A. Adult blood dendritic cells, on the other hand, induce equivalent mitogen responses in cord blood and adult blood T cells. This relative deficiency can be overcome by increasing the concentration of mitogen or the numbers of dendritic cells in the culture. Neonatal primary immune responses may, in part, reflect the reduced function of dendritic cells.

Effect of dexamethasone on IL-2 and IL-3 production by mononuclear cells in neonates and adults

The effect of dexamethasone on interleukin 2 (IL-2) and interleukin 3 (IL-3) production by mononuclear cells in preterm and term infants and adults was evaluated. The capacity of mononuclear cells to produce these cytokines, in preterm infants with bronchopulmonary dysplasia (BPD) and treated with dexamethasone, was compared with that before treatment. Twenty six preterm and 36 term neonates and 24 healthy adults were included in the study. Mononuclear cells isolated from neonatal cord blood (CBMC) and adult peripheral blood (PBMC) were stimulated with phytohaemagglutinin (PHA) in the absence or presence of dexamethasone at concentrations between 10(-8)M and 10(-5)M. IL-2 and IL-3 activities in the supernatant fluids were tested using bioassays. The in vivo effect of the drug on the production of these cytokines by PBMC in 10 preterms was determined before and 24 hours after dexamethasone administration (0.5 mg/kg/day). The production of both cytokines was inhibited in a dose dependent manner. A difference in the sensitivity of mononuclear cells to the inhibitory effect of the drug was found between neonatal cord blood cells and adult PBMC, the former being more sensitive. PBMC from preterm infants treated with dexamethasone for BPD produced significantly less IL-2 and IL-3 as early as 24 hours after the initiation of the treatment (43% and 31%; P < 0.05, respectively). It is concluded that mononuclear cells from preterm and term neonates are more sensitive to the inhibitory effect of dexamethasone on IL-2 and IL-3 production.

Diminished soluble and total cellular L-selectin in cord blood is associated with its impaired shedding from activated neutrophils

We have previously shown that surface levels of the adhesive glycoprotein, L-selectin, are diminished on cord blood neutrophils (polymorphonuclear leukocytes, PMN) and associated with impaired adherence to endothelium under flow conditions. To test the hypothesis that diminished surface levels reflect a total cellular deficiency, we measured L-selectin in PMN lysates and plasma from cord and adult blood. L-selectin content was decreased in cord blood PMN lysates compared with those of adults by both Western blot analyses and ELISA (cord blood, 1195 +/- 160 pg/mL; adult, 1870 +/- 260 pg/mL; X +/- SEM; p < 0.05). Soluble L-selectin levels were also decreased in cord blood plasma (324 +/- 24 ng/mL versus 537 +/- 28 ng/mLiter in adult plasma, p < 0.01). To evaluate L-selectin function, we next compared the dose dependent effect of several chemoattractants on shedding of L-selectin from cord blood and adult PMN. Adult PMN showed greater overall shedding of L-selectin as compared with cord blood PMN after stimulation with fMet-Leu-Phe (p < 0.03) and granulocyte-macrophage colony-stimulating factor (p < 0.02). In contrast, shedding of L-selectin was similar between groups after IL-8 tested stimulation. We conclude that cord blood PMN have a decreased cellular content of L-selectin in addition to an impaired ability to shed surface L-selectin in response to specific inflammatory mediators.

Anergy, AIDS and tuberculosis

Human immunodeficiency virus causes an immunological 'state of anergy'. This state is due to a defective function of antigen-presenting cells, a depletion of CD4+ helper cells, a reduction in the production of soluble factors required for signal transduction, and a decrease in cytotoxic cell activation. The human immunodeficiency virus epidemic has resulted in a global resurgence of tuberculosis. Tuberculin skin testing is negative in 58% of the patients with acquired immunodeficiency syndrome who develop tuberculosis. The mechanism leading to a state of anergy and the mechanism leading to dissemination of dormant tuberculosis appear to be identical.

Effect of neonatal immunization with diphtheria and tetanus toxoids on antibody responses to Haemophilus influenzae type b conjugate vaccines

We randomly assigned 150 newborn infants to receive diphtheria and tetanus toxoids (DT) or Hib oligosaccharide conjugate (HbOC) at birth to determine whether exposure to the Haemophilus influenzae type b (Hib) conjugate vaccines' carrier proteins would enhance immune responses to subsequent administrations of HbOC or PRP-tetanus toxoid conjugate (PRP-T) at 2, 4, and 6 months of age. Their antibody responses were compared with those of 100 children immunized with HbOC or PRP-T beginning at 2 months of age. No serious adverse reactions were associated with neonatal vaccination. Administration of HbOC at birth did not lead to earlier or higher antibody levels. Newborn immunization with DT did not prime children for enhanced antibody responses. Moreover, Hib antibody levels were lower in DT-primed children than in children immunized beginning at 2 months of age. Diphtheria antibody levels, but not tetanus antibody levels, were also lower in children immunized with DT at birth. We conclude that neonatal immunization with Hib conjugate vaccines is not a means to provide earlier protection against invasive Hib disease. Newborn DT administration does not enhance subsequent antibody responses to Hib conjugate vaccines, and may lead to suppression of Hib and diphtheria antibody responses.

Immunology in the pediatrician's office

The development of antibody-mediated immunity is reflected in the maturation of B lymphocytes, in the changing levels of total immunoglobulins, and in the development of specific antibodies first to proteins and then sequentially to different types of polysaccharides. The measurement of anti-pneumococcal antibodies allows us to recognize specific antibody deficiencies, which need to be differentiated from normal developmental phases in the maturation of antibody-mediated immunity. The recognition of the late phase of IgE mediated allergic reactions is important to understanding the chronic manifestations of allergy. Chronic manifestations of allergy are frequently missed because they do not appear to be clearly related to acute triggers of allergic reactions. These conditions can be appropriately diagnosed, prevented, and treated, however, when the mechanisms of the late manifestations of allergy are understood. The integration of knowledge about the development of immunity and of allergic diseases enhances the pediatrician's ability to care for patients with immunologic abnormalities.

Analysis of T helper and antigen-presenting cell functions in cord blood and peripheral blood leukocytes from healthy children of different ages

The development of antigen-specific functional T lymphocyte immunity in infants and children is an area of immunology that needs elucidation. Leukocytes from cord blood (CBL) and from PBL of children of different ages who were in the hospital for minor surgical procedures were compared with PBL from healthy adults for their ability to generate T helper cell (Th) responses assessed by in vitro proliferation and IL-2 production after stimulation with: influenza A virus (FLU); tetanus toxoid (TET); adult allogeneic PBL that were either undepleted (ALLO) or depleted of adherent antigen presenting cells (ALLONW); and PHA. CBL generated Th responses to ALLONW, ALLO, and PHA, but not to FLU or TET. PBL from infants between 6 and 13 mo of age responded to ALLO and PHA; none responded to FLU or ALLONW, and two of four responded weakly to TET. PBL from children between 13 and 26 mo of age responded to all stimuli except FLU, to which only one child responded marginally. PBL from children older than 36 mo responded to all stimuli at levels comparable to those of PBL from adults. The use of undepleted and adherent cell-depleted CBL and PBL from children of different ages as allogeneic stimulators of responses generated by PBL from adults indicated that the antigen presenting function of CBL and PBL from children 13 mo or older are sufficiently developed to present alloantigen, whereas PBL from children younger than 13 mo are not. Therefore, our results indicate that age-dependent differences exist in both T helper and antigen-presenting functions of CBL and PBL from children of different ages. Surprisingly, CBL appear to be more efficient in antigen-presenting function than PBL from children younger than 13 mo. These findings are important for establishing developmental parameters of T helper cell immunity relevant for pediatric infection and transplantation in infants and children.