Objective: To directly assess whether genomewide expression profiles derived from leukocyte subsets are comparable to that of whole blood as measured by enrichment for genes corresponding to metabolic and signaling pathways.
Design: Prospective observational study involving microarray-based bioinformatics based on RNA individually derived from whole blood, neutrophils, monocytes, and lymphocytes, respectively.
Setting: Three pediatric intensive care units in the United States.
Patients: Children ≤10 yrs of age: five normal control subjects and 13 meeting criteria for septic shock on day 1 of presentation to the pediatric intensive care unit.
Interventions: None other than standard care.
Measurements and Main Results: Baseline analyses using whole blood-derived RNA demonstrated increased expression of genes corresponding to signaling pathways involving innate immunity, redox balance, and protein ubiquitination and decreased expression of genes corresponding to the adaptive immune system. Subsequent analyses using leukocyte-specific RNA were congruent with the gene expression profiles demonstrated using whole blood-derived RNA as measured by enrichment for genes corresponding to metabolic and signaling pathways. Gene network analysis, derived from a composite gene list involving the individual gene expression profiles of neutrophils, monocytes, and lymphocytes, respectively, revealed a gene network corresponding to antigen presentation, cell-mediated immunity, and humoral-mediated immunity. Finally, a subanalysis focused on network gene nodes localized to the nuclear compartment revealed functional annotations related to transcriptional repression and epigenetic regulation.
Conclusions: These data demonstrate that genome-level repression of adaptive immunity gene programs early in the course of pediatric septic shock remained evident when analyses were conducted using leukocyte subset-specific RNA.