Effect of steroid hormone and mitomycin C on normal human B lymphocyte colony growth in vitro

We studied the effect of steroid hormone (prednisolone), and mitomycin C on the growth of the B lymphocyte colonies. Also we described an in vitro method for normal human peripheral B cell colony formation. After one day preincubation with 3)μg of PHA-P, irradiated T lymphocytes and a non-T cell population, these lymphocytes were cultured in methylcellulose gel with 30μg of PHA-P. Colonies more than 50 cells were counted under a dissecting microscope. A clear relationship between the number of seeded cells and the growth of colonies was seen in methylcellulose gel. 570±333 colonies per 5.0×105 seeded cells were detected at 4 days of culture. Cells in colonies had surface immunoglobulin as detected using FITClabeled anti-human F (ab)2 rabbit serum by fluorescent microscope, and Giemsa staining revealed differentiation to plasma cells and lymphocytes but no E rosette-forming ability. Then the effect of steroid hormone (prednisolone), and mitomycin C on the growth of B lymphocyte colonies was studied. When these drugs were added for 60 min. before the suspention culture, the inhibition effect of the colony growth was observed by prednisolone but no mitomycin C. When these drugs were added in the semi-solid culture, the inhibition effect of the colony growth was observed with dose dependence. These results suggest that the human B lymphocyte colony forming cells may be noncycling but sensitive to prednisolone.