Supplemental complement component C9 enhances the capacity of neonatal serum to kill multiple isolates of pathogenic Escherichia coli.

Previous studies demonstrated that, compared with adult serum, neonatal serum contained a diminished concentration of complement component C9 and that supplemental C9 enhanced the capacity of neonatal serum to kill an isolate of Escherichia coli. Therefore, experiments were designed to determine the mechanisms by which supplemental C9 enhances the bactericidal capacity of neonatal serum and to determine whether supplemental C9 enhances the capacity of neonatal serum to kill several different pathogenic strains of E. coli. A radiobinding assay and immunogold electron microscopy using a monoclonal anti-C9 antibody revealed that, compared with 40% adult serum, neonatal serum deposited a diminished quantity of C9 onto E. coli O7w:K1:NM. Supplemental C9 (75 mg/L) significantly enhanced the quantity of C9 deposited by the neonatal serum. Treatment with 10 mM MgEGTA (a mixture of 100 mM MgCl2 and 100 mM EGTA that blocks activation of the classic complement pathway but leaves the alternative pathway intact) abolished the capacity of neonatal serum to deposit C9 and to kill the bacteria. Supplemental C9 enhanced the capacity of neonatal serum to kill eight different blood isolates of E. coli. Therefore, supplemental C9 enhanced the capacity of neonatal serum to kill E. coli by increasing the total quantity of C9 deposited via activation of the classic complement pathway. Neonatal serum contained sufficient quantities of classic pathway components, other than C9, to deposit the supplemental C9 onto E. coli and to enhance bacterial killing. The bactericidal activity of neonatal serum against multiple isolates of pathogenic E. coli was increased after C9 supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural colocalization of the bioactive mediators 5-hydroxytryptamine and bombesin in endocrine cells of human fetal airways.

Endocrine cells in the airway epithelium of human fetal lungs are known to contain an amine, 5-hydroxytryptamine (5HT), and a peptide, bombesin (BOM). These mediators may be involved in regulating smooth muscle and secretory activity in the airways as well as in development of the fetal lung. However, the exact endocrine cell type that contains 5HT and BOM has not been described at the ultrastructural level. This investigation provides immunocytochemical evidence that 5HT and BOM are stored in a single cell type, the P1 cell. Thin sections of airways from human fetal lungs were incubated either in anti-5HT antiserum (diluted 1:3000) or in anti-BOM antiserum (diluted 1:600) and then labeled with affinity purified goat anti-rabbit IgG coupled to 16 nm gold particles. For colocalization, thin sections were incubated on one side to demonstrate 5HT and on the other side to demonstrate BOM. Two different sizes of gold particles (10 and 30 nm) were coupled to IgGs and used for the labeled second antibodies. Controls consisted of absorbing of the primary antiserum with an excess of either 5HT or BOM. 5HT- and BOM -like immunoreactivities were observed in the dense-core vesicles (DCV) of P1 cells, and it was apparent from serial sections that 5HT and BOM labeling was sometimes present in the same P1 cells. Sections labeled for 5HT on one side with large gold particles and for BOM on the other side with small gold particles revealed that 5HT- and BOM-like immunoreactivities were located in the same DCV.(ABSTRACT TRUNCATED AT 250 WORDS)