Effect of canine immune serum on the growth of Ehrlichia canis within nonimmune canine macrophages.

The effect of canine immune serum (CIS) on the growth of Ehrlichia canis was studied in macrophage cultures derived from peripheral blood monocytes of normal dogs. Ehrlichiae treated with canine normal serum and then introduced into normal macrophage cultures maintained in canine normal serum multiplied within the macrophages and destroyed them. Immune serum, collected from E canis carrier dogs, suppressed ehrlichial growth in normal macrophages. An inverse relationship existed between the amount of CIS to which ehrlichiae were exposed and the growth of the organism in normal macrophages. The anti-E canis activity was most prevalent in the 7-S fraction of immune serum. Fresh CIS had a greater suppressive effect on the growth of E canis than did heat-inactivated CIS. Antibody cytophilic for canine monocyte-derived macrophages was not detected in CIS.