Abstract
Recent studies have shown that the cell surface properties of Yersinia enterocolitica are altered by the presence of the virulence plasmid, which mediates temperature-inducible outer membrane proteins (OMP). We investigated the interaction of Y. enterocolitica with human polymorphonuclear leukocytes by monitoring luminol-enhanced chemiluminescence (CL) responses. A plasmid-bearing strain grown at 37 degrees C induced four- to sixfold less CL than did the same strain grown at 25 degrees C or a plasmidless, isogenic strain grown at either temperature. Inhibition of CL responses by whole cells was related to plasmid-mediated expression of OMP. The OMP alone could inhibit the CL response of polymorphonuclear leukocytes stimulated by either opsonized zymosan or whole cells of Y. enterocolitica. Pronase treatment of whole cells, which removed the plasmid-mediated OMP, resulted in partial but significant elimination of CL inhibition by whole cells and by OMP derived from them. Incubation with Y. enterocolitica for 60 min did not affect the viability of polymorphonuclear leukocytes. Our results suggest that the interaction of Y. enterocolitica with human polymorphonuclear leukocytes is directly affected by the plasmid-mediated OMP.