PMN LEUKOCYTE MOTILITY/ADHESIVE PROPERTIES IN NEONATES

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Human neonates and infants with protein calorie malnutrition are at high risk for the development of systemic infections resulting from impaired tissue mobilization of phagocytic cells. These investigations will evaluate pathogenic mechanisms that may account for impaired PMN leukocyte and/or monocyte mobilization in these and other high risk populations. Major emphases of these studies will include determinations of functional relationships between cellular adherence and migratory properties, characterization of pathologic cell adhesive properties in these models, and determinants of possible pathologic influences of cytoskeletal proteins on cell translocation and other adherence dependent cell functions. The pathologic contributions to impaired neonatal PMN motility of "adhesive" surface glycoproteins (GP138) will be studied employing fluorescence activated cell sorting, I125 immunoprecipitation (autoradiography) and Na3HB4 labelling techniques and blocking experiments employing specific subunit monoclonal antibodies to OKM-1, LFA-1, and GP138. Functional and structural relationships of GP138 to Triton X Insoluble cytoskeletal "proteins", and chemotactic factor receptors will be evaluated, and the characteristics of "up regulation" and modulation of expression of GP138 will be studied in comparative assessments in neonatal, adult, and GP138 deficient PMNs. Studies of pathologic secretory determinants of impaired motility/adherence of neonatal PMNs including abnormalities of degranulation (lactoferrin RIA), membrane "addition" (TEM morphometry) and/or alterations of cell surface charge (cell electrophoresis), and characteristics of secretion will be quantitatively and temporarily related to GP138 or FMLP receptor "up regulation". Pathogenic mechanisms accounting for impaired microtubule assembly by neonatal leukocytes will be studied by immunochemical characterization of immunoprecipitated tubulin (two dimensional gel electrophoresis) and quantitative assessments of calmodulin in neonatal leukocytes. A further characterization of abnormalities of chemotaxigenesis in healthy and infected neonates and infants with protein calorie malnutrition will be performed employing radioimmunoassays for C3a and C5a, functional assessments of serum chemotactic factors (aggregometry and shape change assays.) The relationship of elevated chemotaxigenesis to the clinical occurence of neutropenia or pulmonary dysfunction in neonates with systemic infection will be determined. Finally, the effects of modified intravenous immunoglobulin administered to healthy neonates with respect to chemotaxigenesis by and opsonophagocytosis for Group B streptococci in vitro will be evaluated. These investigations should provide new information concerning the clinical relevance of in vitro abnormalities of biologic functions of phagocytes, identify clinical risk factors in these and other high risk pediatric hosts, and provide a rationale for preventative or therapeutic approaches to inflammatory dysfunction in these clinical models.