1162 NEUTROPHIL AND MACROPHAGE RESPONSES ELICITED BY MONOCLONAL ANTIBODIES AGAINST GROUP B STREPTOCOCCI

Abstract

Previously we showed that type specific monoclonal antibodies of IgM and IgG2a isotypes protect against intraperitoneal(IP) infection with type III group B streptococci(GBS) in neonatal rats. In contrast, monoclonal IgA does not protect against IP GBS infection. The present study was designed to evaluate mobilization of neutrophils(PMN) and macrophages(M0) in GBS infected neonatal rats. Rats were infected IP with 10⁶ GBS and given buffered saline or type specific IgG, IgM or IgA. Peritoneal lavage and peripheral blood counts were obtained 0, 4, 8, 12 and 20hrs postin-fection. Significantly enhanced PMN responses were seen in IgG and IgM treated rats(4hr-IgG x=38997, IgM 31957, IgA 17981; 8hr-IgG 84127, IgM 57008, IgA 43243, untreated 38120). Peritoneal M0 increased only slightly in IgG or IgM treated rats(NSD). By 20hrs peritoneal PMN in IgG or IgM treated rats actually decreased (IgG 35258; IgM 29538, untreated 46004) as GBS were cleared from blood and peritoneal cavity (GBS culture+ rats-IgG 3/8; IgM 1/6; untreated 6/6). Mobilization was also evaluated using GBS infected polyvinal sponges implanted subcutaneously. Cell recovery from sponges was significantly greater in IgG or IgM treated rats (20 hrs-GBS alone x=300 PMN/2450 M0; IgM 1950/3250; IgG 700/3600; IgA 0/2000). These results suggest that antibody protection is mediated in part by enhanced PMN mobilization to the site of infection. This local PMN response may be essential for protection of human neonates from GBS infection.

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