Binding of antibodies to the surface of the parasitic protozoan Entamo
eba histolytica induces capping and release of antigen-antibody comple
xes, in a process that may be an effective means of evading the host i
mmune response. To analyze the mechanism of capping in E. histolytica
trophozoites, optimal conditions were determined for cap induction by
sera from patients with amebic liver abscess, by polyclonal anti-amebi
c antibodies, and by concanavalin A. Cocapping of actin and myosin was
documented by immunofluorescent staining of capped amebas using phall
oidin, monoclonal anti-actin antibodies, and polyclonal anti-myosin an
tibodies. Immunoblots confirmed the presence of actin and myosin in is
olated caps. These observations demonstrate that amebic cytoskeletal c
omponents participate in E. histolytica capping of surface receptors.
(C) 1994 Academic Press, Inc.