Abstract
We studied the role of the early components of complement (C') in determining clearance of Hib by assessing clearance of Hib in C5 deficient (C5D), in congenic C5 sufficient (CSS) and in cobra-venom treated, C' depleted (CoV) mice. Quantitative blood cultures were done at 10 min, 1hr, 3hr, 24hr and 48hr after iv inoculation of 1-5×105 organisms. C5D cleared Hib as well as CSS mice. However, CoV mice had impaired clearance of Hib as reflected by persistent high grade bacteremla.
Mouse sera contained no antibody to Hib as assessed by an immunofluorescence assay (IFA) and were not bactericidal at concentrations up to 50% (10xACH50). Deposition of C3 was demonstrated by IFA with CSS and C5D sera but not with CoV sera and required Mg++ but not Ca++ implying a role for the alternative pathway (ACP). In this animal model that allows distinction of the opsonic and lytic roles of C', (1) Hib is cleared in the absence of serum bactericidal activity and (2) C3 fixation via the ACP is associated with improved clearance of Hib. C' mediated opsonization rather than lysis may be the important mechanism for defense against Hib in the non-immune host.
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Noel, G., Katz, S. & Edelson, P. CLEARANCE OF HAEMOPHILUS INFLUENZAS TYPE b (Hib) BACTEREMIA REQUIRES C3 FIXATION BUT NOT LYSIS IN THE NONIMMUNE HOST. Pediatr Res 21 (Suppl 4), 331 (1987). https://doi.org/10.1203/00006450-198704010-00982
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DOI: https://doi.org/10.1203/00006450-198704010-00982