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

: The effect of canine immune macrophages and canine immune serum (CIS) on the growth of Ehrlichia canis was studied in vitro. Treatment of E canis organisms with CIS before they were inoculated into immune macrophage cultures, coupled with pre- and postinoculation maintenance of cultures in CIS, suppressed macrophage infection rates to 1% or less. Immune macrophages collected from E canis-carrier dogs and maintained in canine normal serum were more resistant to the intracellular growth of E canis than were normal macrophages maintained in the same serum. Ehrlichiae introduced into normal macrophage cultures maintained in canine normal serum multiplied within the macrophages and destroyed them. Maximal immunity to intracellular growth of E canis, maximal destruction of this organism, or both, required the interaction of E canis with both humoral and cellular factors in proper sequence.