Surface activation markers of T lymphocytes: role in the detection of infection in neonates

Usefulness of the New Hematological Parameter: Reactive Lymphocytes RE-LYMP with Flow Cytometry Markers of Inflammation in COVID-19

Identification of patients with activation of the immune system which indicates the presence of infection is essential, especially in the times of the global coronavirus 2019 (COVID-19) pandemic. The aim of the present study was to evaluate the reactive lymphocytes (RE-LYMP) parameter in COVID-19 and to correlate it with activation lymphocytes markers by flow cytometry. The study group consisted of 40 patients: with COVID-19 infection (n = 20) and with others virus infections without COVID-19 (COVID-19(−) virus (n = 20)) and 20 healthy donors (HC). Blood count and flow cytometry were performed. The COVID-19(+) group had significantly lower RE-LYMP parameter than the COVID-19(−) virus group (5.45 vs. 11.05, p < 0.05). We observed higher proportion of plasmablasts in the COVID-19(+) and COVID-19(−) virus groups than HC (8.8 vs. 11.1 vs. 2.7, p < 0.05). In the COVID-19(+) there was a lower proportion of CD4+ CD38+ cells than in the other groups (significant differences between COVID-19(+) and COVID-19(−) virus groups). RE-LYMP correlated with activated T lymphocytes CD38+ and HLA-DR+ in the COVID-19(−) virus group, however in the COVID-19(+) group correlations with T lymphocytes CD25+ and CD45RO+ were observed. In summary the analysis of the RE-LYMP together with flow cytometric activation markers can be helpful in identifying and distinguishing patients with COVID-19(+) from other viruses and HC.

Multiparameter flow cytometry analysis of leukocyte markers for diagnosis in preterm neonatal sepsis

PURPOSE

Neonatal sepsis is an important public health concern worldwide due to its immediate lethality and long-term morbidity rates, Clinical evaluation and laboratory analyses are indispensable for diagnosis of neonatal sepsis. However, assessing multiple biomarkers in neonates is difficult due to limited blood availability. The aim is to investigate if the neonatal sepsis in preterm could be identified by multiparameter analysis with flow cytometry.

MATERIALS AND METHODS

The expression of activation-related molecules was evaluated by flow cytometry in newborn with or without risk factors for sepsis.

RESULTS

Our analysis revealed that several markers could be useful for sepsis diagnosis, such as CD45RA, CD45RO, or CD71 on T cells; HLA-DR on NKT or classic monocytes, and TREM-1 on non-classic monocytes or neutrophils. However, ROC analysis shows that the expression of CD45RO on T lymphocytes is the only useful biomarker for diagnosis of neonatal late-onset sepsis. Also, decision tree analyses showed that CD45RO plus CD27 could help differentiate the preterm septic neonates from those with risk factors.

CONCLUSIONS

Our study shows a complementary and practical strategy for biomarker assessment in neonatal sepsis.

Immune cell subsets at birth may help to predict risk of late-onset sepsis and necrotizing enterocolitis in preterm infants

BACKGROUND

Parameters predicting late-onset sepsis (LOS) and necrotizing enterocolitis (NEC) in preterm infants would be valuable. Ten-color flow-cytometry enables the estimation of cellular immune status requiring only small sample volumes.

AIMS

Identifying predictive parameters for LOS and NEC in the cellular immune status of preterm infants.

STUDY DESIGN AND SUBJECTS

In this prospective study in 40 preterm infants (week 26+0 to 30+6) and 10 healthy full-term newborn infants (control group, week 37+0 to 40+6), flow cytometric analyses of lymphocyte subpopulations were performed between the 2nd and the 6th day of life, with a follow-up until the preterm infant reached the calculated gestational age of week 40. Patients' episodes of infections and NEC were analyzed according to the NEO-KISS criteria of the German National Reference Center.

RESULTS

Ten preterm infants showed events within the first week of life and were excluded from the analysis. Of the other 30, five developed NEC, twelve LOS. In patients with LOS, the proportion of double-negative (DN) T cells was significantly elevated compared to patients without LOS, while immune-regulatory CD56bright and CD56negCD16+ NK cells were significantly decreased (p<0.05). Patients with NEC showed a reduction in the NK cell proportion (<3.7%) and significantly decreased naïve cytotoxic CD45RA+CD62L+ T cells (p<0.05).

CONCLUSION

NK cells and DN-T cell counts within the first week of life may be predictors for NEC and LOS in preterm infants. In order to identify patients at risk early, further analysis of these populations might be of interest.

Phenotypic characterization of bovine memory cells responding to mycobacteria in IFNγ enzyme linked immunospot assays

Bovine tuberculosis (bTB) remains a globally significant veterinary health problem. Defining correlates of protection can accelerate the development of novel vaccines against TB. As the cultured IFNγ ELISPOT (cELISPOT) assay has been shown to predict protection and duration of immunity in vaccinated cattle, we sought to characterize the phenotype of the responding T-cells. Using expression of CD45RO and CD62L we purified by cytometric cell sorting four distinct CD4(+) populations: CD45RO(+)CD62L(hi), CD45RO(+)CD62L(lo), CD45RO(-)CD62L(hi) and CD45RO(-)CD62L(lo) (although due to low and inconsistent cell recovery, this population was not considered further in this study), in BCG vaccinated and Mycobacterium bovis infected cattle. These populations were then tested in the cELISPOT assay. The main populations contributing to production of IFNγ in the cELISPOT were of the CD45RO(+)CD62L(hi) and CD45RO(+)CD62L(lo) phenotypes. These cell populations have been described in other species as central and effector memory cells, respectively. Following in vitro culture and flow cytometry we observed plasticity within the bovine CD4(+) T-cell phenotype. Populations switched phenotype, increasing or decreasing expression of CD45RO and CD62L within 24h of in vitro stimulation. After 14 days all IFNγ producing CD4(+) T cells expressed CD45RO regardless of the original phenotype of the sorted population. No differences were detected in behavior of cells derived from BCG-vaccinated animals compared to cells derived from naturally infected animals. In conclusion, although multiple populations of CD4(+) T memory cells from both BCG vaccinated and M. bovis infected animals contributed to cELISPOT responses, the dominant contributing population consists of central-memory-like T cells (CD45RO(+)CD62L(hi)).

Effect of major burns on early and late activating markers of peripheral blood T lymphocytes

It is known that lymphocytes immunophenotype is a reflection of the functional level of the immune system. The immunosuppressive effect of major burns is also known for many years. T lymphocytes of 50 major burn patients were analyzed in base line (BL) samples at 24 hours and at 1 week and 2 weeks after burn, using monoclonal antibodies of CD3, CD4, CD8, CD25 (IL2R) and HLA-DR by flow cytometry and β2-microglobulin (β2-m) by ELISA. Recorded values were compared with those of 50 healthy donors. There was statistically significant reduction in absolute number of CD3 positive cells (CD3+) (p<0.000) and CD4/CD8 ratio (p=0.01) in the first 24 hours in comparison with controls. CD25 (IL-2R) shows insignificant upregulation on T lymphocytes after burn with significant upregulation of HLA-DR. The absolute number of CD3+ cells began to increase after 2 weeks (p=0.03) but remained less than controls (p=0.08). CD4/CD8 ratio was more or less same as healthy controls after 2 weeks. Upregulation of CD25 was insignificantly increased and that of HLA-DR was markedly increased after 2 weeks (p=0.001). Significant negative correlations were detected between mean values of β2-m and both absolute numbers of CD3 and CD4 positive cells in BL and one week samples. In addition there was significant correlation between mean values of β2-m and values of CD25 expression in the BL samples. The obtained data is suggestive of persistent activation of T lymphocytes two weeks after major burns whereas early shedding of β2-m is related to activation of lymphocytes increasing their susceptibility to apoptosis, both indicative of altered immune response. Burn intensivists and surgeons should be keen to support the patients' immune system in the first hours following major burns. This support will ensure free-bacteremic blood with a consequent better prognosis.

T Lymphocyte Activation Profiles in Peripheral Blood of Long-Versus Short-Term Residents of Kuwait: Comparison with Asthmatics

Introduction: During the Arabian Gulf Wars of 1991 and 2003, the resident population of Kuwait sustained heavy exposure to environmental toxicants introduced by military activities. No comprehensive studies have been conducted to assess how exposure to the wartime and postwar environment may have altered the fundamental patterns of immune reactivity among Kuwaitis in ways that affect pathogenesis of disease. This present study addresses this issue by characterising immunological features of asthma and allergies in a Kuwaiti population that is unique and possibly correlates with toxicant exposures. Materials and Methods: Twenty-five long-term residents of Kuwait afflicted with bronchial asthma concurrent with rhinitis; and 2 healthy control groups: 18 long-term residents and 10 newcomers to Kuwait were evaluated by 2- and 3-colour flow cytometry for peripheral blood T cell subpopulation frequencies. Results: Relative to healthy, long-term residents, significantly elevated frequencies of all activated cell phenotypes were observed in the blood of the asthmatic group (P <0.05 to P <0.001), except for CD8+HLA-DR+ cells and a presumed T-regulatory (Treg) subpopulation: CD4+CD25high. The asthmatic group was also observed to have larger populations of CD3+ (pan-T cells), CD4+ (T helper cells) and CD8+ (cytotoxic T cells), CD3+CD56 (NKT-like cells) and CD56+CD16+ (NK cells) compared to healthy long-term residents. Compared to healthy recent immigrants, the blood of long-term residents contained elevated levels of CD3+CD56+ (NK-like), CD4+CD45RA+/CD45RO+ (Naive-to-Memory Transitional), but lower CD4+CD25+high (Treg) (P <0.05). Conclusions: Elevated representation of natural killer (NKT)-like and memory phenotypes may predispose long-term residents towards enhanced susceptibility for airway disease; while at the same time, reducing representation of Treg cells which are protective against airway disease, and this may increase vulnerability to these syndromes among the residents of Kuwait. These results may provide insight into the features of immunopathogenesis of asthma and allergies in Kuwait that arise as a result of the special environment of the country. Key words: Asthma, Immune reactivity, Kuwait, Rhinitis, T cells

T cell activation in abnormal perinatal events

The aim of this study was to determine the percentage of CD45RO(+) T cells in umbilical cord blood from neonates born at less than 37 weeks of gestation. Fifty-nine patients were enrolled in this study, including 49 with preterm and 10 with term deliveries. Preterm deliveries were divided into two categories; spontaneous (Group A, n= 31) and indicated (Group B, n= 18). Perinatal infection was categorized as C-CAM, H-CAM and neonatal infection. The percentage of CD45RO(+) T cells in the umbilical cord was assessed using flow cytometry. IL-6 was measured using ELISA. In Group A, the percentage of CD45RO(+) T cells and concentrations of IL-6 in patients with perinatal infection (n= 18) were significantly higher than in those without perinatal infection (n= 13). A significant correlation between percentage of CD45RO(+) T cells and IL-6 concentrations was observed in the cord blood (r= 0.62, P= 0.001). In Group B, pink-tinged amniotic fluid was observed in seven cases. In these cases, an increase in the percentage of CD45RO(+) T cells (>10%) was noted. In the cases without perinatal infection, which included all those delivered at term (n= 32), no correlation was observed between the percentage of CD45RO(+) T cells and gestational age at delivery (r=-0.139, P= 0.448). We concluded that a high percentage of CD45RO(+) cord blood T cells is observed not only in perinatal infection, but also in the presence of abnormal perinatal events such as maternal bleeding in preterm gestation.

Unexplained fetal death is associated with changes in the adaptive limb of the maternal immune response consistent with prior antigenic exposure

OBJECTIVE

The causes of fetal death are largely unknown. CD4 T cells have been classified according to the expression of the CD45 isoforms into 'naive-like' T cells (CD45RA) and 'memory-like' T cells (CD45RO). An increase in the percentage of the CD45RO has been interpreted as indicating prior antigenic exposure of the host and, in newborns, evidence of infection. The purpose of this study was to determine whether unexplained fetal death was associated with a change in the proportion of 'naive-like' and 'memory-like T cells' in the maternal blood, as determined by the CD45 isoforms on the surface of CD4+ lymphocytes.

STUDY DESIGN

A prospective study was conducted to compare the CD45 sub-population of lymphocytes in patients with intrauterine fetal death (n = 26) and normal pregnancy (n = 89). The percentages of CD45RA+, CD45RO+ and CD45RA+/CD45RO+ on CD4+ T lymphocytes were determined in maternal blood using flow cytometry and monoclonal antibodies. Results were reported as a percentage of CD4+ lymphocytes. Non-parametric statistics were used for analysis. A p value of < 0.05 was considered significant.

RESULTS

Patients with intrauterine fetal death had a higher percentage of CD45RO+ CD4+ T lymphocytes than normal pregnant women (fetal death: median 57.7%, range 35.4-78.6 vs. normal pregnancy: median 49.9%, range 19.1-86.8; p = 0.004). Fetal death was associated with a lower median percentage of CD45RA+ CD4+ lymphocytes than in normal pregnant women (fetal death: median 32.3%, range 15.3-58.0 vs. normal pregnancy: median 40.2%, range 11.2-67.3; p = 0.01). There was no significant difference in the percentage of cells with dual expression (CD45RA+/CD45RO+) between the study groups.

CONCLUSION

Prior exposure to microbial products (bacterial or viral) or other unidentified antigens may result in a shift of the sub-population of 'naive-like' T cells to 'memory-like' T cells in mothers with unexplained fetal death.

Chemotactic mediators of Th1 T-cell trafficking in smokers and COPD patients

Chronic obstructive pulmonary disease (COPD) is smoking-related and associated with increased cytotoxic CD8+ T-cells in the airway. There is a wide range of susceptibility to the damaging effects of cigarette smoke with only a small proportion of smokers progressing to COPD. We have previously reported increased intracellular Th1 cytokines in blood, BAL and intraepithelial CD8+T cells in current and ex-smokers with COPD, whereas healthy smokers showed localized Th1 response in the lung only. We thus hypothesised that Th1-associated chemokines or their receptors on CD8+T-cells may be differentially expressed in the blood of healthy smokers, current smoker COPD subjects and those who had ceased smoking. We investigated chemokines, chemokine receptors and Th1 and cytotoxic T-cell markers in blood and BAL using flow cytometry, ELISA and cytometric bead array. In blood, CXCR3, CCR4, intracellular CCR3 and the Th1 marker 62L(-)CD45RO(+) were increased in both COPD groups and healthy smokers. In contrast, cytotoxic T-cells, ITAC, MIG, IFN-gamma and CCR5 were increased in both COPD groups but not smokers. In BAL, the Th1 marker 62L(-)CD45RO(+), CCR5, CXCR3, IFN-gamma, RANTES, IL-8, MCP-1, MIG and ITAC were increased in both COPD groups and smokers versus controls. Our findings are consistent with systemic inflammation in COPD associated with an increased influx of cytotoxic and Th1 cells into the airway. The differential expression of specific chemokines and their receptors in blood from COPD subjects and healthy smokers suggests that inclusion of these markers in any panel designed for the non-invasive investigation of smokers with a disposition to COPD would be clinically relevant.

Insulin-like growth factor I promotes cord blood T cell maturation through monocytes and inhibits their apoptosis in part through interleukin-6

Background

The functional immaturity of T cells contributes to the susceptibility of neonates to infections and the less severe graft-versus-host disease associated with cord blood (CB) transplantation. We have previously reported that insulin-like growth factor – I (IGF-I) promotes the phytohaemagglutinin (PHA)-induced CB T cell maturation and inhibits their apoptosis in mononuclear cell (MC) culture. We hypothesized that the effects of IGF-I may be mediated by accessory cells and soluble factors.

Results

This study showed that the kinetics of PHA-induced maturation in purified CD3+ T cell was delayed compared to that in CBMC. The addition of autologous CD14+ monocytes increased T cell maturation and potentiated the effect of IGF-I. The addition of IL-6 had no effect on CB T cell maturation but it reduced PHA-induced apoptosis significantly. We further demonstrated that the neutralisation of IL-6 in CBMC culture partially abrogated the anti-apoptotic effect of IGF-1 on T cells. The anti-apoptotic effect of IL-6 was not mediated via the reduction of Fas expression in T cell subsets.

Conclusion

Our results suggested that the maturation effect of IGF-1 is partially mediated by monocytes and the anti-apoptotic effect in part via IL-6. Further investigation is needed to explore the therapeutic use of IGF-I in enhancing neonatal immunity.

Neonates with culture proven sepsis have lower amounts and percentage of CD45RA+ T cells

To evaluate the expression of lymphocyte subsets in newborns diagnosed as culture proven or culture negative sepsis and to investigate the differentiation. The aim of this study is to explore neonatal immunology in newborns diagnosed as culture proven or culture negative neonatal sepsis and to identify their place in the diagnosis. This prospective study was performed in newborns who were diagnosed as neonatal sepsis and hospitalized in a tertiary care hospital and who were classified as culture proven sepsis (n=12), as culture negative sepsis (n=21) and healthy (n=17). Lymphocyte subsets were obtained at time of diagnosis. Culture proven sepsis had statistically significant increase of WBC compared to culture negative sepsis and control groups (p<0.05). Significant decreases were observed of percentage of lymphocyte, when compared to culture negative sepsis and control group (p<0.05). Percentage of CD4(+) was lower in culture proven sepsis and absolute count of CD4(+) was lower in culture negative sepsis (p<0.05). Percentage and absolute count of CD45RA(+) were lower in culture negative sepsis than control and percentage of CD45RA(+) was lower in culture proven sepsis than control (p<0.05). Percentage of CD45RO(+) was higher in culture proven sepsis than control group (p<0.05). It is clear that during neonatal sepsis lymphocyte subsets are different from healthy controls. Whether the described abnormalities represent the absence of a normal maturation process, rather, pathological events is still not clear.

Biomarkers in neonatal infection

Infected newborn infants are often difficult to differentiate from patients suffering from noninfective diseases. Whilst delaying treatment with antibiotics of infected infants may be fatal, widespread indiscriminate use in all cases with suspected bacterial infection could lead to both drug-induced complications and the development of multidrug-resistant organisms. Conventional biomarkers, such as blood cell counts and morphology, have serious limitations. Investigators in this area of research have, therefore, made strenuous efforts to discover more reliable biomarkers with superior diagnostic utilities and clinically relevant characteristics to help neonatal clinicians differentiate between infected and noninfected infants. The major classes of biomarkers in neonatal infection of recent interest will be discussed, including: acute phase reactants, cytokines, chemokines and leukocyte surface antigens. The application of these biomarkers to derive prognostic information useful to neonatal clinicians will also be considered.

Increased airway granzyme b and perforin in current and ex-smoking COPD subjects

Increased bronchial epithelial cell apoptosis and CD8+ T-cell numbers in the blood and airways have been reported in COPD. These cells can induce apoptosis via the granzyme-b/perforin-mediated pathway. We hypothesized that increased levels of granzyme-b/perforin would be detected in COPD, contributing to apoptosis and tissue damage. Intracellular granzyme-b/perforin were measured in blood-derived T-cells and natural killer (NK) cells from COPD subjects (30 current and 30 ex-smokers), 20 asymptomatic current-smokers and 30 never-smokers, and bronchoalveolar lavage (BAL)-derived T-cells from a cohort of these subjects using flow cytometry. Soluble granzyme-b was determined by ELISA. In blood, there was an increased percentage of T-cells expressing intracellular granzyme-b/perforin for both COPD groups but not asymptomatic smokers (versus never-smokers). Soluble granzyme-b was undetectable. In BAL, soluble granzyme-b levels and the percentage of T-cells expressing intracellular granzyme-b/perforin were increased in both COPD groups and asymptomatic smokers. There was a significant correlation between granzyme-b expression in BAL and apoptosis of bronchial epithelial cells. Most circulating NK cells expressed granzyme-b/perforin, with the median fluorescence intensity of staining increased in both COPD groups and asymptomatic smokers. Granzyme-mediated apoptosis may thus be one mechanism of lung injury in COPD. The changes that persist despite smoking cessation in COPD likely reflect pathophysiological changes in COPD as opposed to the effects of smoking per se.

Diagnostic markers for neonatal sepsis

PURPOSE OF REVIEW

To review the current evidence on the use of infection markers for diagnostic evaluation of sepsis in neonates.

RECENT FINDINGS

Recent research in immunology has led to the discovery of cell surface antigens, chemokines, cytokines and acute phase proteins that can potentially be used to 'rule in' or 'rule out' sepsis. The diagnostic utilities of key inflammatory mediators, including CD11b, CD64, interleukin-6 and interleukin-8, are promising and likely to become increasingly used as markers of infection for both diagnostic and prognostic purposes.

SUMMARY

Serial measurements and use of combinations of markers have been reported to improve sensitivity and negative predictive value of these tests. Current markers are not infallible, however, and do not permit neonatologists to withhold antibiotics in sick infants with suspected infection. Thus, many have emerged as useful indicators for early discontinuation of unnecessary antimicrobial therapy. Some infection markers are also useful for identifying infants with severe infection and adverse prognosis. Advances in flow cytometry have allowed simultaneous measurement of key markers using only minimal blood volume. Judicious selection of a panel of markers with complementary properties could greatly increase the ability of neonatologists to diagnose infection and discern valuable prognostic information.

Differential Rates of Apoptosis in Bronchoalveolar Lavage and Blood of Lung Transplant Patients

BACKGROUND

Lung transplant tolerance depends on effective control of T-cell proliferation and activation. Commonly used immunosuppressive agents promote peripheral blood-derived lymphocyte apoptosis and inhibit production of cytokines involved in lymphocyte proliferation and survival. However, there have been no studies of the effectiveness of immunosuppressive treatments on apoptosis of T cells derived from the airways of lung transplant recipients. Our main aim was to compare apoptosis of T cells derived from peripheral blood and bronchoalveolar lavage (BAL) from lung transplant recipients, with no evidence of chronic or acute cellular rejection, and healthy volunteers. Lung transplantation may also be associated with increased apoptosis of airway epithelial cells. To investigate this possibility, we also examined apoptosis of epithelial cells derived from bronchial brushing.

METHODS

BAL, blood, and bronchial brushings were obtained from lung transplant recipients (n = 9) and age-matched controls (n = 15). T cell and epithelial cell apoptosis, Fas, Bax, Bcl-2, and p53 were evaluated by flow cytometry.

RESULTS

Increased apoptosis of peripheral blood T cells and decreased Bcl-2 were observed in the transplant patients. In contrast, there was no significant change in apoptosis of airway T cells or apoptosis-related proteins. Increased apoptosis and increased p53 were observed in the airway epithelial cells from the transplant recipients, possibly as a result of ineffective control of infiltrating cytotoxic T cells.

CONCLUSIONS

Immunosuppressive agents may not be as effective in inducing apoptosis of airway-derived T cells as peripheral blood-derived T cells after lung transplantation. These findings may have implications on the outcome of the immune response in the airways after immunosuppressive therapy and may be particularly relevant to lung allograft rejection.

Immunologic markers in the neonatal period: diagnostic value and accuracy in infection

Diagnosis of early-onset neonatal infection has led to the development of several screening tests including C-reactive protein, a very commonly used marker, and cytokines (mainly interleukin-6 and -8), alone or in combination with C-reactive protein, based on the premise that their increases in response to infection may precede that of C-reactive protein. In recent years the search for diagnostic tests has turned to procalcitonin, a propeptide of calcitonin, which appears to be a promising marker of infection in newborn infants. Additionally, specific leukocyte cell surface antigens (mainly CD11b and CD64), detected by flow cytometry, are evaluated as markers of neonatal infection, since their expression on the cell membrane increases in substantial quantities after leukocyte activation by bacteria or their cellular products. This review aims to examine the role of these newly available immunologic indices and to assess their validity as diagnostic markers of infection during the neonatal period.

Neutrophil CD64 is a sensitive diagnostic marker for early-onset neonatal infection

This prospective study aimed to evaluate the diagnostic utilities of neutrophil CD64 expression for the identification of early-onset clinical infection and pneumonia in term infants and to define the optimal cutoff value so that it may act as a reference with which future studies can be compared. Term newborns in whom infection was suspected when they were <72 h of age were recruited into the study. C-reactive protein (CRP) and expression of CD64 on neutrophils were measured at 0 h (at the time of sepsis evaluation) and 24 h. The sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of CRP, CD64, and the combination of these two markers for predicting neonatal sepsis were determined. A total of 338 infants with suspected clinical sepsis were investigated, 115 of whom were found to be clinically infected. CRP and CD64 in infected infants were both significantly elevated at 0 and 24 h compared with noninfected infants (p < 0.001). The calculated optimal cutoff value for CD64 was 6136 antibody-phycoerythrin molecules bound/cell. CD64 has a very high sensitivity (96%) and NPV (97%) at 24 h. The addition of CRP only marginally enhanced the sensitivity and NPV (97 and 98%, respectively). In conclusion, neutrophil CD64 is a very sensitive diagnostic marker for the identification of early-onset clinical infection and pneumonia in term newborns. The results strongly suggest that measurement of neutrophil CD64 may allow neonatal clinicians to discontinue antibiotic treatment at 24 h in infants who are clinically stable and whose CD64 expressions are below the optimal cutoff level.

CD25+CD4+ T cells in human cord blood: an immunoregulatory subset with naive phenotype and specific expression of forkhead box p3 (Foxp3) gene

OBJECTIVE

To address the role of cord blood (CB) CD25+CD4+ T cells, the gene expressions and function of this subset were analyzed.

MATERIALS AND METHODS

CD25+CD4+ T cells fractionated from CB of term and preterm infants were subjected to flow cytometry, quantitative polymerase chain reaction analysis for cytokines, costimulatory molecules, and transcription factors, and functional assays.

RESULTS

Human preterm CB contained a high proportion of CD25+CD4+ T cells that declined with gestational age to the level of adult peripheral blood (PB). CD25+ or CD25-CD4+ T cells in CB had a higher frequency of CD45RA+ and CD38+ cells than in PB. CB CD25+CD4+ T cells less frequently expressed CD45RO, CD71, and HLA-DR than PB CD25+CD4+ T cells, despite similar expressions on CB and PB CD25-CD4+ T cells. No expression of IL-10, transforming growth factor-beta, interleukin-4, and interferon-gamma mRNA differed between CB CD25+CD4+ and CD25-CD4+ T cells, in contrast to the high interleukin-10 expression in PB CD25+CD4+ T cells. CTLA-4 was more transcribed in CB and PB CD25+CD4+ T cells than in the counterpart CD25-CD4+ T cells. CD28 or ICOS was similarly expressed in CB and PB T cells. CB CD25+CD4+ T cells effectively suppressed the proliferation of CB CD25-CD4+ T cells in a dose-dependent manner. Human CB and PB CD25+CD4+ T cells preferentially transcribed Foxp3, which governs the regulatory function of this subset in mice.

CONCLUSIONS

These results suggest that CB contains CD25+CD4+ regulatory T cells as a functionally mature population with naive phenotype. This subset may naturally arise and decline in fetus to play a potential immunoregulatory role in intrauterine life.

Maternal and Neonatal Lymphocyte Subpopulations at Delivery and 3 Days Postpartum: Increased Coexpression of CD45 Isoforms

PROBLEM

Huge physiologic changes during parturition involve immune cells. Alterations in maternal and neonatal lymphocytes postpartum might ascertain the subpopulations that are most affected and may possibly be of importance in the process.

METHOD OF STUDY

Peripheral blood was taken from 20 healthy women at vaginal delivery and 3 days later, concomitantly with cord and peripheral blood from their newborns. Lymphocyte immunophenotyping was done by three-color flow-cytometry.

RESULTS

Maternal T helper cells were decreased and natural killer (NK) cells were significantly increased during labor. Percentage of CD4(+) and percentage and absolute count of CD8(+) cells coexpressing CD45RA and CD45RO antigens were higher than 3 days later. In cord blood NK cells were considerably increased and more CD4(+) cells expressed CD45RO antigen.

CONCLUSION

Coexpression of CD45RA and CD45RO molecules indicates activation of maternal CD4(+) and CD8(+) lymphocytes. NK cells increase suggests their possible association with parturition processes. Lymphocyte subsets in cord blood correspond to maternal subsets to some extent.

Immunologic monitoring of maintenance therapy for acute lymphoblastic leukaemia in children-preliminary report

BACKGROUND

In the study we evaluated immune reconstitution during maintenance therapy for acute lymphoblastic leukaemia (ALL) in relation to different treatment protocols and response of the immune system to the accompanying infections.

PROCEDURE

The study group consisted of 40 children. The BFM protocol'90 was used in the standard risk group, while the New York protocol-in the high risk group. Assessment of the immune system was based on the analysis of peripheral blood mono-nuclear cells by flow cytometry and concentrations of immunoglobulins: G, M, A and IgE. Each patient was examined at 1-3 months' intervals.

RESULTS

Following cessation of intensive therapy, the successive months of maintenance treatment showed: (1) a considerable depletion of B lymphocytes, a durable decrease in IgM, IgA and gradually increasing IgG; (2) a correlation between the time passing from the cessation of intensive therapy and increased numbers and percentage of B cells, and the helper/suppressor cell ratio. In the group of children treated according to the high risk protocol, compared to the low-risk group patients, we found lower levels of the following parameters: IgG, % lymphocytes: B and T lymphocytes (including CD4/CD8 ratio and "naive"/"memory" ratio) and NK cells (% and count). During infection: (1) a significant increase was noted in the percentage of T cells with HLA co-expression and monocytes with ICAM-1 co-expression, (2) the percentage of CD3(+)CD45RO(+) "memory" T cells was found to increase.

CONCLUSIONS

Our findings indicate quantitative and qualitative changes of the immunity in children with ALL during maintenance therapy.

Diagnostic markers of infection in neonates

Diagnostic markers of infection are useful indicators of neonatal sepsis. Serial measurements of infection markers can improve diagnostic sensitivity, and the use of multiple markers can enhance diagnostic accuracy. Current evidence suggests that promising markers may be useful for early termination of antimicrobial treatment, but none of the current diagnostic tests are sensitive and specific enough to influence the clinical decision for withholding antibiotic treatment at the onset of suspected infection.

Multiple leucocyte activation markers to detect neonatal infection

Diagnosis of congenital or neonatal infection is often based on clinical signs. However, clinical symptoms of infections may not be specific, and for this reason early diagnosis is often determined on results of laboratory tests, which may not currently be adequate. A more reliable method of detection of infection may be the demonstration of activated lymphocytes, which can be conducted rapidly and before the isolation of the infected organism. We have shown that detection of up-regulation of CD45RO, an activated/memory isoform of CD45 present on T cells, provides a reasonably sensitive screening test for neonatal infection. We also showed that dual expression of CD45RA/CD45RO was up-regulated early during the infective process in neonates with documented infection. However, other leucocytes are also activated during the infective process. To improve the sensitivity of the neonatal infection screening test and to identify the types of leucocytes involved in the immune response to the infective organism, we studied further the up-regulation of a comprehensive range of surface activation markers on T cells, monocytes and natural killer (NK) cells from a group of 17 newborn patients with positive culture, a group of 40 possibly infected patients based on clinical signs and a control group. 'Normal' ranges were established for each activation marker for each leucocyte subset from 1 to 7 and 7-14-day-old newborns <35 weeks' gestation and 35-40 weeks' gestation. There was a significant increase in the percentage of T cells expressing CD25 in the peripheral blood from infants at 2 weeks of age. Expression of HLA-DR on T cells, CD25 and CD69 on monocytes and HLA-DR on NK cells was also increased significantly in the peripheral blood from infants at 2 weeks of age and may reflect a maturation of these functional surface molecules. Up-regulation of CD69 on NK cells was the most sensitive marker for neonatal sepsis (positive in 13/16 patients). CD69 and CD25 expression was increased significantly on T cells in 11/17 and 10/17 patients, respectively. A combination of CD45RA/CD45RO and CD45RO identified 11/16 infected patients. Measurement of CD69 expression on NK cells with CD45RA, CD45RO, CD25 and CD69 expression on T cells resulted in a significant increase in at least two leucocyte activation markers from infected patients. In conclusion, this is the first report of the up-regulation of CD69 on NK cells as a sensitive marker of neonatal infection. A combination of this marker with CD45RA, CD45RO, CD25 and CD69 expression on peripheral blood derived T cells is the most sensitive and specific for neonatal infection.

Soluble L-selectin, a marker of immune activation, in neonatal infection

L-Selectin is an adhesion molecule shed from the surface of lymphocytes and granulocytes upon activation. Soluble L-selectin in the plasma can thus reflect immune activation and is elevated in several pathological states. Our objective was to evaluate plasma levels of L-selectin as an immune activation marker in neonates and to determine whether it can serve as a marker of infection, either neonatal or congenital, or if it is affected by the mode of delivery and obstetrical or perinatal complications. A solid-phase ELISA was used on 89 sera from neonates less than 2 days of age, according to the manufacturer's instructions. Levels of soluble L-selectin in the neonate were lower than those of older infants and children and comparable to the levels seen in adults. There was no difference between levels of soluble L-selectin of premature (median, 1172 ng/ml) and full-term babies (median, 1151 ng/ml) or between babies born via vaginal (median, 1233 ng/ml) or cesarean delivery (median, 1146 ng/ml). Conditions such as preeclampsia or administration of steroids to the mother did not affect the levels of L-selectin in the neonate. In contrast, the presence of maternal clinical chorioamnionitis resulted in an increase in levels of L-selectin in the neonate (median, 1377 vs 1072 ng/ml, p = 0.02), as did neonatal sepsis (median, 1331 vs 1149 ng/ml, p = 0.026). Soluble L-selectin, and thus immune activation level, is highest in neonates with neonatal infection and needs to be further evaluated as a surrogate marker for diagnosing sepsis in the neonate.

A marked decrease in L-selectin expression by leucocytes in infants with Bordetella pertussis infection: leucocytosis explained?

OBJECTIVE

Infants with Bordetella pertussis infection (whooping cough) have an unexplained lymphocytosis and leucocytosis characterized by an increase in small lymphocytes with convoluted and cleaved nuclei. To characterize these cells immunophenotyping using multiparameter flow cytometry was performed on leucocytes from a group of 11 infants aged 3-6 months with proven pertussis and from uninfected control subjects.

METHODOLOGY

The panel of monoclonal antibodies used to elucidate leucocyte subtypes included activation, adhesion, costimulatory, memory, T-helper (Th) 1 and Th2 markers.

RESULTS

Patients with pertussis showed an increase in absolute numbers of neutrophils, monocytes, T lymphocytes (both CD4 and CD8), B lymphocytes (including CD10+/CD19+ haematogones) and natural killer (NK) cells. All leucocyte subgroups showed a marked decrease in L-selectin (CD62L) expression. The expression of other adhesion molecules CD11a, CD44 and CD54 on all leucocyte subgroups was unchanged. Expression of costimulatory molecules, CD49D and CD28 on T cells and CD80 and CD86 on monocytes, was unchanged. Lymphocyte activation markers CD69, CD25 and HLA-DR were unchanged. There was an increase in CD45RA+/CD45RO+/CD4+ cells (activated) and CD62L-/CD45RO+/CD4+ cells (Th1-like) but no increase in CD7-/CD4+ T cells (Th2-like).

CONCLUSIONS

L-Selectin expression mediates extravasation of leucocytes into tissues and is important for homing of peripheral blood lymphocytes to lymph nodes. The significant down-regulation of L-selectin on leucocytes in pertussis infection may prevent leucocyte migration to areas of infection and homing and adhesion of T and B cells to peripheral lymphoid tissues. The increase in lymphocytes with Th1 phenotype may be required for effective immune response to the infective organism. These data provide a possible explanation for the absolute leucocytosis observed in this disease.

Maternal lymphocyte subpopulations (CD45RA+ and CD45RO+) in preeclampsia

OBJECTIVE

The maternal syndrome of preeclampsia has been attributed to a systemic intravascular inflammatory response and endothelial cell dysfunction. The stimulus responsible for intravascular inflammation in preeclampsia has not been determined. The expression of CD45 isoforms on the surface of human T cells has been used to classify CD4(+) T lymphocytes into naïve cells (CD45RA+) and memory T cells (CD45RO+). An increased percentage of CD45RO+ cells has been interpreted as consistent with previous exposure to microbial products or other antigens. The purpose of this study was to determine whether preeclampsia is associated with a change in the proportion of CD45RA+ and CD45RO+.

STUDY DESIGN

A prospective study was conducted in patients with preeclampsia (n = 24) and normal pregnancy (n = 75). The percentage of CD45RA+ and CD45RO+ on CD4(+) T lymphocytes in peripheral blood was determined using flow cytometry and monoclonal antibodies. Results were reported as a percentage of CD4(+) lymphocytes. Parametric statistics were used for analysis. A probability value of <.05 was considered statistically significant.

RESULTS

Patients with preeclampsia had a significantly higher percentage of CD45RO+ than normal pregnant women (P <.01). A significantly lower percentage of CD45RA+ was found in patients with preeclampsia than in normal pregnant women (P <.01).

CONCLUSION

Preeclampsia is associated with an increase in the percentage of CD45RO+ and a decrease in the CD45RA+ lymphocyte subpopulation. Therefore, patients with preeclampsia have evidence of previous antigenic exposure, the nature of which remains to be established.

Neutrophil CD64 expression: a sensitive diagnostic marker for late-onset nosocomial infection in very low birthweight infants

This study aims to evaluate the diagnostic utilities of four leukocyte surface antigens-two lymphocyte antigens (CD25 and CD45RO) and two neutrophil antigens (CD11b and CD64)-for identification of late-onset nosocomial bacterial infection in preterm, very low birthweight infants, and to define the optimal cutoff value for each marker so that it may act as a reference with which future studies can be compared. Very low birthweight infants in whom infection was suspected when they were >72 h of age were eligible for the study. A full sepsis screen was performed in each episode. IL-6, C-reactive protein, and leukocyte surface antigens (CD25, CD45RO, CD11b, and CD64) were measured at 0 (at the time of sepsis evaluation), 24, and 48 h by standard biochemical methods and quantitative flow cytometric analysis. The diagnostic utilities including sensitivity, specificity, and positive and negative predictive values of each marker and combination of markers for predicting late-onset neonatal infection were determined. One hundred twenty-seven episodes of suspected clinical sepsis were investigated in 80 infants. Thirty-seven episodes were proven infection. The calculated optimal cutoff values for CD25, CD45RO, CD11b, and CD64 were 3,100, 2,900, 10,450, and 4,000 phycoerythrin-molecules bound per cell, respectively. An interim analysis of data after 68 episodes suggested that CD25 and CD45RO were poor predictors of neonatal infection with sensitivity or specificity <75% during a single measurement. Thus, these two markers were excluded from further investigation. In the final analysis, CD64 has the highest sensitivity (95-97%) and negative predictive value (97-99%) at 0 and 24 h after the onset. The addition of IL-6 or C-reactive protein (0 h) to CD64 (24 h) further enhanced the sensitivity and negative predictive value to 100%, and has the specificity and positive predictive value exceeding 88% and 80%, respectively. Neutrophil CD64 expression is a very sensitive marker for diagnosing late-onset nosocomial infection in very low birthweight infants. If further validated, the use of CD64 as an infection marker should allow early discontinuation of antibiotic treatment at 24 h without waiting for the definitive microbiologic culture results. The quantitative flow cytometric analysis applied in this study could be developed into a routine clinical test with high comparability and reproducibility across different laboratories.

CD45RA and CD45RO isoforms in infected malnourished and infected well-nourished children

The aim of this study was to determine if the distribution in vivo of CD4(+)CD45RA(+)/CD45RO(-) (naive), CD4(+)CD45RA(+)/CD45RO(+) (Ddull) and CD4(+)CD45RO(+) (memory) lymphocytes differs in malnourished infected and well-nourished infected children. The expression of CD45RA (naive) and CD45RO (memory) antigens on CD4(+) lymphocytes was analysed by flow cytometry in a prospectively followed cohort of 15 malnourished infected, 12 well-nourished infected and 10 well-nourished uninfected children. Malnourished infected children showed higher fractions of Ddull cells (11.4 +/- 0.7%) and lower fractions of memory cells (20.3 +/- 1.7%) than the well-nourished infected group (8.8 +/- 0.8 and 28.1 +/- 1.8%, respectively). Well-nourished infected children showed increased percentages of memory cells, an expected response to infection. Impairment of the transition switch to the CD45 isoforms in malnourished children may explain these findings, and may be one of the mechanisms involved in immunodeficiency in these children.

Preoperative prediction of postoperative edema and effusion in pediatric cardiac surgery by altered antigen expression patterns on granulocytes and monocytes

Postoperative edema and effusion (POEE) following cardiopulmonary bypass (CPB) surgery in children retards recovery and may aggravate postpericardiotomy (PPS), capillary leak syndrome (CLS), or multiorgan failure (MOF). Compared with complication-free children, POEE affected children have different preoperative serum levels of circulating cytokines and adhesion molecules. These levels may be used preoperatively to assess POEE, but their determination is time consuming, costly, and a substantial blood volume is required. Altered serum levels of cytokines and adhesion molecules also may be reflected in altered antigen expression on circulating blood leukocytes. The predictive potential of flow cytometric (FCM) leukocyte immunophenotyping was explored as a sensitive and fast method that required small blood samples. Blood samples taken 24 h preoperatively from 49 patients (3-18 years old) were stained with monoclonal antibodies for adhesion molecules (ICAM-1, LFA-1, Mac-1) or constitutive/activation markers (CD4, CD14, CD16, CD25, CD54, CD69, HLA-DR) and measured on a microbead calibrated FCM. Neutrophils, monocytes, and eosinophils from POEE patients express higher preoperative levels of LFA-1, monocytes, HLA-DR, and other activation markers (all P < 0.03). Over 89% of the patients were classified correctly by using two discriminant analysis methods (sensitivity, >76%; specificity, >86%; positive prediction, >80%; negative prediction, >83%). Granulocytes and monocytes of postoperative POEE patients exhibit significant preoperative immune activation, suggesting an increased risk for patients with atopic/allergic predisposition. Surgical trauma and CPB cause additional immune activation, leading to POEE by a summative response. Most patients at risk for POEE can be identified preoperatively by using data pattern analysis on FCM-derived parameters.

Neonatal (cord blood) T cells can competently raise type 1 and 2 immune responses upon polyclonal activation

In the neonate, cellular immunity has generally been hypothesized as being incompetent. Accumulating evidence from several recent studies, together with our present report, contradicts this hypothesis. T-helper cell and T cytotoxic type 1 and 2 (Th1/Th2 and Tc1/Tc2, respectively) cytokine responses to polyclonal T cell receptor (TCR) activation were assessed in medium-term cultures of human cord blood T cells using intracellular cytokine staining, which could measure the frequencies of cytokine-producing cells. In this study, we examined the responses of cord blood CD4(+) and CD8(+) T cells in regard to the production of interferon (IFN)-gamma and interleukin (IL)-4 and compared the responses with those obtained from T cells of healthy adults. We found that the responses in cord blood T cells activated with TCR stimulation were comparable to those of their adult counterparts. Moreover, the Th/Tc cells that developed in cord blood were as competent as adult cells for both IFN-gamma and IL-4 secretion. In addition, IL-12 production, which is critical for both Th1 and Tc1 responses, was equally comparable in the two groups. The production of two major cross-regulatory cytokines, tumor necrosis factor-alpha and IL-10, was similarly comparable and not significantly different between the two groups. Taken together, these results indicate that, though naive, the neonatal T cell is competent to respond to TCR-mediated stimulation and to produce both type 1 and type 2 cytokines.

Leucocyte activation markers in clinical practice

The response against tissue injury and infection begins with the early activation of molecular and cellular elements of the inflammatory and immune response. Severe tissue injury, necrosis, and infection induce imbalanced inflammation associated with leukocyte over-stimulation and excessive or dysregulated release of cellular mediators. Clinical and experimental studies have shown that these mediators are directly related to progressive post-injury complications. Persistent increased levels of pro-inflammatory mediators produce tissue injury. Excessive production and activity of anti-inflammatory mediators cause anergy and/or immune dysfunction with increased susceptibility to infection. Leukocyte activation is assessed by cell surface phenotype expression, cellular mediators determination, or by measuring functional responses using isolated cells. Potential routine clinical uses are: evaluation of severity and prognosis in critically ill patients, immunomonitoring of sepsis, and detection of tissue injury, necrosis, and infection. In practice, the determination of cellular activation markers is restricted by a limited number of automated methods and by the cost of reagents. The availability of flow cytometry and immunoassay automated systems can contribute to a wider use in practice. Here we review the immunopathophysiology of polymorphonuclear neutrophil, monocyte, macrophage, and lymphocyte activation in response to tissue injury and infection. In addition, laboratory methods for their determination, and clinical applications in practice, are discussed.

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.