PMN MOTILITY AND ADHERENCE IN NEONATES

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Human neonates and individuals with heritable Mac-1, LFA1 deficiency are at high risk for the development of infectious complications resulting from impaired tissue mobilization of phagocytic cells. These studies will evaluate pathogenic mechanisms that may account for impaired PMN or mononuclear leukocyte mobilization in these populations. Major emphases will include determinations of: a) functional relationships between cellular adherence and migratory properties, b) mechanisms regulatin the induction, modulation and functional activation of cellular adherence by inflammatory stimuli, and c) possible pathologic influences of cytoskeletal proteins (microtubules) on cell translocation. They will focus on the contributions of a family of "adhesive" glycoproteins (GPs) (Mac-1, LFA1, p150,95) to adherence-dependent properties of leukocytes; comparative studies employing neonatal and Mac-1 deficient cells will allow a unique opportunity to understand functional and clinical consequences of abnormal expression. Surface expression of Mac-1 GP when mediated by chemotactic or secretory stimuli will be quantitated using immunofluorescence flow cytometry and 125I immunoprecipitation techniques employing monoclonal antibodies (MAb); their topographical relationships to other surface reptors (FcR and CR1) and to "adhesion sites" will be evaluated by IIF microscopy. MAbs to each Mac-1 subunit will be employed in blocking experiments to assess their functional contributions to adhesion-dependent cell functions including microtubule and microfilament assemblage (IIF tubulin and actin probes). The relationships of Mac-1 GP "up regulation", hyperadherence and secretory events will be studied and possible secretory determinants of impaired Mac-1 GP induction and hyperadherence of neonatal PMNs will be assessed. Subcellular fractionation and a new concanavalin A binding assay will be employed to determine the location of intracellular Mac-1 pools and to evaluate mechanisms regulating their surface expression, redistribution and/or recycling. Selected pathogenic mechanisms accounting for disturbed MT assembly of neonatal PMN including: abnormal cell adherence-dependent cytoskeletal activation, abnormal post-translational tubulin tyrosylation, or intrinsic immunochemical abnormalities of or Alpha or Beta tubulin will be evaluated with intracellular immunofluorescence probes under conditions promoting MT assembly or disassembly. These studies should provide a basis for understanding the functional and clinical consequences of disturbed adhesion-dependent cellular functions in the inflammatory response, and potentially allow the development of therapeutic strategies in these and other high risk pediatric models.