ROLE OF YADA IN RESISTANCE OF YERSINIA-ENTEROCOLITICA TO PHAGOCYTOSISBY HUMAN POLYMORPHONUCLEAR LEUKOCYTES

Pathogenic Yersinia enterocolitica cells do not induce the chemilumine scence response of human polymor-phonuclear leukocytes (PMNs). We test ed the chemiluminescence response to Y. enterocolitica mutants affecte d in the known pYV-encoded factors. We did not detect any influence of the Yops in this phenomenon. By contrast, the presence of YadA correl ated with a lack of chemiluminescence. The expression of YadA at the b acterial surface also reduced the phagocytosis by PMNs. Finally, we me asured the survival of Y. enterocolitica cells confronted with PMNs by the classical plating method and by a new luminometry assay. We obser ved that YadA(+) bacteria were not killed, while YadA(-) bacteria were killed. We conclude that the presence of YadA at the surface of Y. en terocolitica cells prevents phagocytosis and killing by PMNs. This con clusion is in good agreement with our recent observation that YadA pro tects Y. enterocolitica from opsonization by C3b.