Propagation of Anaplasma marginale in bovine lymph node cell culture.

Anaplasma marginale was propagated in cell cultures derived from bovine lymph node (LN). Treatment of host cells with diethylaminoethyl dextran (DEAE-D) before inoculation and centrifugation of inoculum onto the monolayers resulted in significant numerical increases of A marginale. The direct fluorescent antibody technique (FAT) was used for detection of the organism in culture. The rat was combined with the standard microscopic count procedure to obtain numerical estimates of the organism in cell culture. Infection of LN cells was irregular, with some cells containing many organisms and others containing none. The organisms were dispersed or in inclusions in the cytoplasm of LN cells. Numerical increases of organisms occurred within 6 hours and these were greatest at 12 to 24 hours. After 24 hours, the organisms decreased rapidly, but small numbers of them were observed for at least 7 days. The average generation time in culture was approximately 17.1 hours.