1276 FUNCTIONAL BACTERIAL OPSONIC ACTIVITY OF HUMAN AMNIOTIC FLUID

Abstract

There is some data to suggest that amniotic fluid (AF) protects the fetus from invasion by pathogenic bacteria. To examine methods by which AF may offer such protection, quantitative antibody, complement activity, and functional opsonic capacity were measured. Immunoglobulins were measured by laser nephelometry and total hemolytic complement by radial diffusion; results suggested activity adequate for bactericidal capacity. The chemiluminescence assay was used to quantitate the functional interaction between PMN's and E. coli, group B strep (GBS) or zymosan particles preopsonized with amniotic fluid obtained at different stages of gestation. Results were compared to those for normal serum. Data were analyzed by evaluation of the initial slope, area under the curve, and peak chemiluminescence response. Opsonic activity of amniotic fluid for E. coli and GBS was demonstrated with E. coli showing greater reactivity(maximum cpm= 15-25,000) than GBS(10-20,000 cpm). Specific, as well as nonspecific, opsonic activity was demonstrated by absorption of AF with killed bacteria. Concentration of amniotic fluid did not result in an increase in chemiluminescent activity demonstrating that optimal opsonic activity already exists. The classical and alternate pathways of complement were assessed for E. coli and GBS. Amniotic fluids preterm did not differ from term pregnancies. This study demonstrates that amniotic fluid can provide the fetus with protection from bacterial pathogens and delineate mechanisms for such protection.