Effect of polyinosinic-polycytidylic acid on the number of colony-forming cells in the hematopoietic organs of guinea pigs

An increase in the number of cells forming discrete colonies in monolayer cultures of myelokaryocytes (colony-forming cells) was observed in guinea pigs 8–24 h after receiving an intraperitoneal injection of polyinosinic-polycytidylic acid in a dose of 300μg/kg. The number of colony-forming cells in the spleen was reduced at these same time after injection of the compound. After 3 days the number of colony-forming cells in the spleen increased, but in the bone marrow it decreased. These values returned to normal 14 days after injection of the compound. The changes observed are evidently explainable on the grounds that the compound has a marked effect on the fraction of colony-forming cells in hematopoietic organs that are stromal elements of the stem-cell type.