Open AccessSpecific antibody promotes opsonization and PMN‐mediated killing of phagocytosis‐resistant Enterococcus faecium
Author(s) -
Rakita Robert M.,
Quan Van C.,
JacquesPalaz Karen,
Singh Kavindra V.,
Arduino Roberto C.,
Mee Mee,
Murray Barbara E.
Publication year - 2000
Publication title -
fems immunology & medical microbiology
Language(s) - English
Resource type - Journals
eISSN - 1574-695X
pISSN - 0928-8244
DOI - 10.1111/j.1574-695x.2000.tb01489.x
Subject(s) - antibody opsonization , phagocytosis , microbiology and biotechnology , biology , enterococcus faecium , antibody , immune system , complement system , alternative complement pathway , opsonin , immunology , antibiotics
Many clinical isolates of Enterococcus faecium are resistant to neutrophil (PMN)‐mediated phagocytosis and killing in the presence of normal human serum. We have now examined the ability of specific polyclonal rabbit antibodies to promote opsonization and killing of phagocytosis‐resistant E. faecium . Immune rabbit serum generated against formalin‐killed E. faecium TX0016, a phagocytosis‐resistant strain, markedly promoted binding of TX0016 organisms to PMNs and PMN‐mediated killing. These effects were dramatically reduced by (a) adsorption of immune serum with E. faecium TX0016, but not by adsorption with a strain of E. faecium susceptible to phagocytosis, and (b) incubation of immune serum with carbohydrate purified from TX0016, but not by incubation with a surface protein extract from TX0016. IgG purified from immune serum was unable by itself to promote bacterial binding to PMNs. However, specific IgG was able to promote binding to PMNs and PMN‐mediated killing in the presence of normal human serum as a complement source, as were F(ab′) 2 and Fab fragments produced from it, and the alternative pathway of complement was sufficient to promote IgG‐ and F(ab′) 2 ‐mediated opsonization. PMN complement receptor type 3, but not complement receptor type 1, was involved in bacterial binding to PMNs induced by the combination of F(ab′) 2 fragments and normal human serum. These results suggest that opsonization by antibodies potentially directed against bacterial carbohydrate, in conjunction with complement activation, has an important role in the host defense against phagocytosis‐resistant E. faecium .