INFLUENCE OF BONE MARROW ON REPOPULATION OF THYMUS IN X-IRRADIATED MICE

A quantitative cellular study of the irradiated mouse thymus and bone marrow has been presented. The bone marrow cells were classified into two populations, according to their volume. One of these cell populations is mainly composed of lymphocytic and the other of granulocytic cells. These two populations showed dissimilar repopulation patterns after whole body irradiation. The thymus cell population exhibited a repopulation pattern closely resembling that of the bone marrow lymphocyte population, both after whole and partial body irradiation. Bone marrow shielding during a second irradiation, 8-26 days after the first one, accelerated the thymus repopulation if the second dose was given at a time when the bone marrow was composed predominantly of small cells. An attempt was also made to purify the bone marrow lymphocytes by treating bone marrow cells in vitro with desoxycholate. It was observed that transplantation of desoxycholate-resistant cells into lethally irradiated mice induced an earlier repopulation of the thymus than an equal number of normal bone marrow cells. © 1969.