Cell-mediated and humoral immune responses of German shepherd dogs and beagles to experimental infection with Ehrlichia canis.

The cell-mediated and the humoral immune responses of 12 German Shepherd Dogs and 5 Beagles inoculated with Ehrlichia canis were evaluated. Results indicated that specific and nonspecific immunosuppression due to E canis occurred in the German Shepherd Dogs. Canine leukocyte migration-inhibition factor was successfully isolated and shown to be physically and functionally similar to human and guinea pig migration inhibition factor. Of the German Shepherd Dogs, 58% developed positive cell-mediated responses; 80% of the Beagles became positive. German Shepherd Dogs that developed severe chronic ehrlichiosis did not respond to as great a degree as did the German Shepherd Dogs and Beagles with mild chronic disease. The cell-mediated responses decreased with time and disappeared by 147 days after inoculation. Humoral antibody titers in all inoculated dogs increased with time and remained at increased concentrations. Treatment of four inoculated dogs with antilymphocyte serum did not modify the course of the disease. The findings indicated that cell-mediated immunity may have a significant role in determining the course of disease in dogs infected with E canis.