M fermentans infection induces continued growth of human peripheral blood mononuclear cells. PBMCs isolated from 2 healthy blood donors (K4117 and K4119) cultured in alpha-MEM containing 20% fetal bovine serum, 1 μg/mL of cyclosporine A, 10^-6 M of dexamethasone, and 10^-5 M of β-mercaptoethanol were infected with 10⁶ CCU/mL of M fermentans (Mi strain). Noninfected control culture was inoculated with equal volume of SP4 medium. All cultures were kept in a 37°C, 5% CO₂ incubator and fed twice a week by replacing the top half of the culture with the same medium without cyclosporine A, dexamethasone, and β-mercaptoethanol. Viable cells were examined by trypan blue staining and counted in a hemacytometer.