Antibody Secreting Cell and Cyotokine Profiles in Neonates on ECMO

Specific Aims Primary Objective 1\. Determine the rise, peak, and fall of immunoglobulin isotype-specific ASC's, and immunoactive proteins (cytokines and chemokines) from sequential samples of peripheral blood from infants on ECMO. Secondary Objectives: 1. Determine the most appropriate time to sample blood from infants with suspected sepsis for ASC diagnostic assay. 2. Characterize the incidence of culture-negative sepsis that leads to ECMO. 3. Determine immunoglobulin isotype-specific levels of ASC in infants with and without infection. 4. Establish an archive of mononuclear cells and plasma to use in development of pathogen specific ASC assays. Hypothesis Infants on ECMO will have a high ASC response and unique cytokine/chemokine patterns due to possible underlying infection and exposure to many foreign antigens (blood products, ECMO circuit). A significant portion of these will have ASC's with specificity for common causes of neonatal sepsis that is not detected by routine blood culture. Procedures: Residual samples will be collected from those used in routine procedures for infants on ECMO. The approximate volume/sample will be 0.5-0.8ml. Specimens will be processed using methods well established in our laboratory. Briefly, PBMC's will be isolated via Ficoll gradient and archived in liquid nitrogen at -80C. Batch analysis of ASC levels and lymphocyte proliferation activity will be performed when sufficient number of specimens are accumulated. A detailed profile and quantification of immune cells will be determined by Fluorescent Activated Cell Sorter (FACS) staining for CD3, CD4, CD8, CD27, CD38, CD45, and HLA-DR. A bead micro-array will be used to detect levels of immunoactive molecules, also done on the FACS. The proteins detected will include, but may not be limited to, the following: IL1β, IL2, IL4, IL5, IL6, IL7, IL8, IL10, IL12p70, IL13, IL17, GCSF, GMCSF, IFN-γ, MCP-1, MIP-1β, TNFα. The ASC procedure be that established by Van de Verg modified to use membrane surface microculture plates in place of agar with outcomes read by CTL analyzer in place of manual count. LPA assays will use long established techniques.