Antibody-dependent cell-mediated cytotoxicity in cattle infected with Babesia bovis (Babes, 1888) : characterization of the host immunoglobulins, efficiency of host effector cells and comparison with serological tests

Abstract

A stabilate prepared from Babesia bovis-infected Boophilus microplus ticks was used to infect intact adult cattle. Whole sera and isolated immunoglobulins were used to determine serologic activity during both initial and challenge infections. The isolation of immunoglobulins from representative sera were obtained by various column chromatography techniques to identify the specific antibody classes and/or subclasses involved. Bovine IgM, IgG₁ and IgG₂ were successfully isolated using Sephacryl S-200 gel filtration, QAE Sephadex A-50 and DEAE Sephadex A-50 ion-exchange chromatography. The purity of these isolated immunoglobulins was assessed using immunoelectrophoresis and crossed electrophoresis. During these procedures, a subcomponent of IgG₂ was isolated and termed IgG₂[subscript a]. Complement-fixing antibody and immunofluorescent antibody activities were detected in sera from cattle with initial and challenge infections. Specific IgM and IgG₁ were reactive in both tests with IgG₁ responsible for the development and maintenance of high titers. There was evidence for the presence of multiple antigens in both tests based on the kinetics of the activity of IgM and IgG₁. There was also evidence for differing specificity within the IgG₁ fraction. ...