Somatic cell hybrids of canine peritoneal macrophages and SV40-transformed human cells: derivation, characterization, and infection with Ehrlichia canis.

Somatic cell hybrids were obtained by fusion of canine peritoneal macrophages and SV40-transformed human skin fibroblasts. A cell line (WRH-2) was established from a single isolated hybrid clone. The WRH-2 cell line has been serially passaged 60 times and has a population doubling time of approximately 24 hours. Karyotypic analysis showed the modal number of chromosomes to be 80, with a selective segregation of canine chromosomes. Expression of incorporated canine DNA was substantiated by cellular enzyme activities and antigen expression. The susceptibility of 5% to 7% of WRH-2 cells to Ehrlichia canis infection was associated with phagocytic properties of these cells. Magnetic separation of phagocytic cells after ingestion of carbonyl iron resulted in a significant enhancement of the phagocytic population with a concomitant increase in the percentage of cells susceptible to ehrlichial infection. Serial passage of the selected subpopulation of hybird cells, however, resulted in a rapid diminution in the percentage of phagocytic cells.