| Abstrakt: |
Neonatal group B streptococcal pneumonia is a severe disease, often resulting in death. Autopsy findings resemble those of hyaline membrane disease. Numerous organisms may be seen in the alveoli, but few polymorphonuclear leukocytes (PMNs) are found in the areas of bacterial invasion. Aggregated PMNs are often found, however, in the pulmonary capillaries. This study was designed to explore the effect of the group B streptococcal (GBS) type III antigen on PMN chemotaxis and PMN-endothelial cell interactions. Human PMNs were isolated and pretreated with 0.25 to 4 micrograms/ml of GBS type III antigen prior to determining their chemotactic response to the chemoattractants formyl-methionyl-leucyl-phenylalanine, zymosan-activated serum, platelet-activating factor, and leukotriene B4. The GBS antigen caused a concentration-dependent inhibition of formyl-methionyl-leucyl-phenylalanine, zymosan-activated serum, and platelet-activating factor-mediated chemotaxis (% inhibition of 38.1 +/- 4.0, 55.5 +/- 3.3, 46.7 +/- 9.7%, respectively; p less than 0.01). Leukotriene B4-mediated chemotaxis was not significantly depressed (21.2% +/- 7.7 inhibition; NSD). Group B streptococcal antigen also inhibited formyl-methionyl-leucyl-phenylalanine-induced PMN adherence to endothelial cells in a concentration-dependent fashion when incubations were performed in the absence of serum. In contrast, incubation of GBS type III antigen with serum deficient in antibody to GBS resulted in a marked enhancement of PMN attachment to human endothelial cells. No significant enhancement of adherence was sen with the antigen in the presence of serum containing GBS type III antibody. These data suggest that the GBS type III antigen by itself may inhibit the influx of PMNs into the local site of infection in the alveoli.(ABSTRACT TRUNCATED AT 250 WORDS) |
