Kinetics of antibody response to Ehrlichia canis assayed by the indirect fluorescent antibody method.

The kinetics of antibody production response to experimentally induced infection of dogs with Ehrlichia canis was determined by ion-exchange and molecularsieve chromatography and by indirect fluorescent antibody (IFA) test. The first IFA antibody at 7 days after inoculation resided in immunoglobulin M (IgM) and immunoglobulin A (IgA) classes. At approximately 21 days after inoculation, the antibody was in IgM, IgA, and immunoglobulin G (IgG) classes. Thereafter, antibody concentrations continued to increase in the IgG class; those in the other 2 immunoglobulin classes had a variable pattern. In 2 dogs which died 60 and 114 days after inoculation, a decrease of antibody concentration in the 3 immunoglobulin classes was evident at the time of death. In the carrier dog, however, which was killed 147 days after inoculation, antibody concentrations sustained increasing titers in the 3 immunoglobulin classes.