title: A group B streptococcal extract reduces neutrophil counts and induces neutrophil aggregation.
abstract: The possibility that group B streptococci (GBS) may induce neonatal neutropenia by promoting neutrophil aggregation and the entrapment of aggregates in the lung was studied in vivo and in vitro utilizing a cell free GBS extract [(GBS)-trichloroacetic acid (TCA)]. The intravenous infusion of the extract into neonatal lambs induced reductions of circulating white blood cells (0 time, 3.1 X 10(3)/mm3 +/- 0.5 versus 2.2 X 10(3)/mm3 +/- 0.7) 5 min after infusion (p less than 0.01). At necropsy these lambs had prominent accumulation of polymorphonuclear leukocytes in their pulmonary interstitium. Subsequently, neutrophil aggregation was studied by incubating GBS-TCA in human serum or phosphate-buffered saline with subsequent addition to human polymorphonuclear leukocytes in an aggregometer. GBS-TCA incubated in human serum induced prompt polymorphonuclear leukocyte aggregation (mean delta T 12.3% +/- 2.8 in human serum versus delta T 2.5% +/- 2.1 in phosphate-buffered saline, p less than 0.001). Preincubation of GBS-TCA followed by incubation in human serum with human GBS hyperimmune IgG significantly reduced aggregation (GBS-TCA in serum mean delta T 14.9 +/- 2.44 versus 5.42 +/- 1.80, p = 0.002). Cell-free GBS products may induce polymorphonuclear leukocyte aggregation in the presence of whole serum. This phenomenon might contribute to the pulmonary injury experienced by infants with GBS pneumonia and sepsis.
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000276:immunology; D002449:Cell Aggregation; D005260:Female; D006358:Hot Temperature; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology; D066298:In Vitro Techniques; D007231:Infant, Newborn; D007958:Leukocyte Count; D008168:Lung / Q000473:pathology; D008297:Male; D009504:Neutrophils / Q000276:immunology*; D012756:Sheep; D013292:Streptococcus agalactiae / Q000276:immunology*; D014238:Trichloroacetic Acid
chemical_list: D007136:Immunoglobulins; D014238:Trichloroacetic Acid