Objective To prospectively evaluate relationships among serum cytokine levels, innate immune responsiveness, and mortality in a multicenter cohort of critically ill children with influenza infection. Design Prospective, multicenter, observational study. Setting Fifteen pediatric ICUs among members of the Pediatric Acute Lung Injury and Sepsis Investigators network. Patients Patients ≤18 yrs old admitted to a PICU with community-acquired influenza infection. A control group of outpatient children was also evaluated. Interventions ICU patients underwent sampling within 72 hrs of ICU admission for measurement of a panel of 31 serum cytokine levels and quantification of whole blood ex vivo lipopolysaccharide-stimulated tumor necrosis factor-α production capacity using a standardized stimulation protocol. Outpatient control subjects also underwent measurement of tumor necrosis factor-α production capacity. Measurements and Main Results Fifty-two patients (44 survivors, eight deaths) were sampled. High levels of serum cytokines (granulocyte macrophage colony-stimulating factor, interleukin-6, interleukin-8, interferon-inducible protein-10, monocyte chemotactic protein-1, and macrophage inflammatory protein-1α) were associated with mortality (p < 0.0016 for each comparison) as was the presence of secondary infection with Staphylococcus aureus (p = 0.007), particularly methicillin-resistant S. aureus (p < 0.0001). Nonsurvivors were immunosuppressed with leukopenia and markedly reduced tumor necrosis factor-α production capacity compared with outpatient control subjects (n = 21, p < 0.0001) and to ICU survivors (p < 0.0001). This association remained after controlling for multiple covariables. A tumor necrosis factor-α response <250 pg/mL was highly predictive of death and longer duration of ICU stay (p < 0.0001). Patients with S. aureus coinfection demonstrated the greatest degree of immunosuppression (p < 0.0001). Conclusions High serum levels of cytokines can coexist with marked innate immune suppression in children with critical influenza. Severe, early innate immune suppression is highly associated with both S. aureus coinfection and mortality in this population. Multicenter innate immune function testing is feasible and can identify these high-risk children.

Background Critical injury has been associated with reduction in innate immune function in adults, with infection risk being related to degree of immune suppression. This relationship has not been reported in critically injured children. Hypothesis Innate immune function will be reduced in critically injured children, and the degree of reduction will predict the subsequent development of nosocomial infection. Materials and Methods Children (≤ 18 years of age) were enrolled in this longitudinal, prospective, observational, single-center study after admission to the pediatric intensive care unit (PICU) following critical injury, along with a cohort of outpatient controls. Serial blood sampling was performed to evaluate plasma cytokine levels and innate immune function as measured by ex vivo LPS-induced TNFα production capacity. Results Seventy-six critically injured children (and 21 outpatient controls) were enrolled. Sixteen critically injured subjects developed nosocomial infection. Those subjects had higher plasma IL-6 and IL-10 levels on post-trauma day (PTD) 1–2 compared to those who recovered without infection and outpatient controls. Ex vivo LPS-induced TNFα production capacity was lower in children on PTD 1–2 (p=0.006) and over the first week following injury (p=0.04) in those who went on to develop infection. A TNFα response of < 520 pg/ml at any time in the first week after injury was highly associated with infection risk by univariate and multivariate analysis. Among transfused children, longer red blood cell storage age, not transfusion volume, was associated with lower innate immune function (p < 0.0001). Trauma-induced innate immune suppression was reversible ex vivo via co-culture of whole blood with GM-CSF. Conclusions Trauma-induced innate immune suppression is common in critically injured children and is associated with increased risks for the development of nosocomial infection. Potential exacerbating factors, including red blood cell transfusion, and potential therapies for pediatric trauma-induced innate immune suppression are deserving of further study.

Intensive cardiopulmonary support plays an important and potentially life-saving role in the care of pediatric stem cell transplant patients. Survivors of intensive support do not have compromised 1-year survival or organ function compared with children who did not receive intensive support.

IntroductionInnate immune suppression occurs commonly in pediatric critical illness, in which it is associated with adverse outcomes. Less is known about the adaptive immune response in critically ill children with sepsis. We designed a single-center prospective, observational study to test the hypothesis that children with septic shock would have decreased adaptive immune function compared with healthy children and that among children with sepsis, lower adaptive immune function would be associated with the development of persistent infection or new nosocomial infection.MethodsChildren (18 years or younger) who were admitted to the pediatric intensive care unit with septic shock (by International Consensus Criteria) were enrolled in the study. Blood samples were taken within 48 hours of sepsis onset and again on Day 7 of illness. Adaptive immune function was assessed with ex vivo phytohemagglutinin (PHA)-induced cytokine production capacity of isolated CD4+ T cells. Percentage of regulatory T cells was measured with flow cytometry. Absolute lymphocyte counts were recorded when available.ResultsIn total, 22 children with septic shock and eight healthy controls were enrolled. Compared with those from healthy children, CD4+ T cells isolated from septic shock children on Days 1 to 2 of illness and stimulated with PHA produced less of the pro-inflammatory cytokine interferon gamma (IFN-γ) (P = 0.002), and the antiinflammatory cytokines interleukin (IL)-4 (P = 0.03) and IL-10 (P = 0.02). Among septic shock children, those who went on to develop persistent or nosocomial infection had decreased T-cell ex vivo PHA-induced production of IFN-γ (P = 0.01), IL-2 (P = 0.01), IL-4 (P = 0.008), and IL-10 (P = 0.001) compared with septic shock children who did not. Percentage of regulatory T cells (CD4+CD25+CD127lo) did not differ among groups.ConclusionsAdaptive immune suppression may occur early in the course of pediatric septic shock and is associated with adverse infection-related outcomes.

Critically ill children with severe sepsis or septic shock demonstrate early innate and adaptive immune suppression. Early innate and adaptive immune suppression are associated with longer durations of organ dysfunction and may be useful markers to help guide future investigations of immunomodulatory therapies in children with sepsis.

rs12252 was not associated with susceptibility to influenza-related critical illness in children or with critical illness severity. Our data also do not support it being a splice site.

BACKGROUND Reduced monocyte function is associated with adverse outcomes from critical illness. PRBC are thought to impair monocyte function but relationships between PRBC storage solution and monocyte suppression are unknown. This study was designed to test the hypothesis that immunosuppressive effects of PRBC on monocytes are related to both storage time and preservative solution. STUDY DESIGN AND METHODS Monocytes from healthy adult donors were co-cultured with PRBC that had been stored in AS-1, AS-3, or CPD-only for 7, 14, or 21 days. Cells were then stimulated with LPS and their supernatants assayed for TNFα and IL-10. Transwell experiments were performed to evaluate the role of cell-to-cell contact. Monocyte mRNA expression was quantified by RT-PCR. RESULTS LPS-induced TNFα production capacity was reduced compared to controls for all groups, but CPD-only PRBC suppressed monocyte function more than PRBC stored in AS-1 (p = 0.007) and AS-3 (p = 0.006). IL-10 production was preserved or augmented in all groups. Longer storage time was associated with reduced TNFα production capacity for AS-1 and AS-3 groups but not CPD. Preventing cell-to-cell contact did not eliminate the inhibitory effect of PRBC on monocyte responsiveness. PRBC exposure was associated with decreased LPS-induced TNFA mRNA expression (p < 0.05 for all groups). CONCLUSIONS CPD-only PRBC suppressed monocyte function more than PRBC stored with additive solutions. TNFα production was reduced even in the absence of cell-to-cell contact and was impaired at the mRNA level. Further work is needed to understand the role of preservative solutions in this process.

SYNOPSIS While many forms of critical illness are initiated by a pro-inflammatory stimulus, it is now understood that a compensatory anti-inflammatory response can occur concurrently with systemic inflammation. When severe, this is termed immunoparalysis and it represents an important form of acquired immunodeficiency. Immunoparalysis can affect the innate and adaptive arms of the immune system and is characterized by reduced monocyte HLA-DR expression, reduced cytokine production capacities upon ex vivo stimulation of leukocytes or whole blood, the presence of lymphopenia, and by increase expression of inhibitory cell surface molecules such as PD-1. Immunoparalysis has been associated with increased risks for nosocomial infection and death in a wide variety of pediatric critical illnesses. Evidence suggests that immunoparalysis is reversible through treatment with immunostimulants such as GM-CSF or interferon-γ. Highly standardized, prospective immune monitoring regimens are needed in order to better understand the immunologic effects of ICU treatment regimens and to enrich clinical trials with subjects most likely to benefit from immunostimulatory therapies.