Haemopoiesis in murine bone marrow and spleen after fractionated irradiation and repeated bone marrow transplantation. II. Granulopoiesis.

Granulopoiesis was studied in mice repeatedly subjected to individual doses of 3 Gy of 60Co gamma-rays at 4-day intervals up to a total dose of 24 Gy on the basis of total bone marrow cellularity follow-up and analysis of myelograms and splenograms. Half of the mice received 10(6) nuclear cells of syngeneic bone marrow after each fractional radiation dose. After an initial steep decrease, the number of granuloid cells in the spleen increased about 30-fold between days 12 and 16 of the experiment (total dose 9 and 12 Gy, respectively). This increase was temporary and between days 20 and 24 (total dose 15 and 18 Gy, respectively) a steep decrease again occurred. At a low level (below 10% of the control value) remained the granuloid cells in the spleens of bone marrow recipients until the end of the experiment (day 37, total dose 24 Gy). The behaviour of the granuloid compartment of haemopoiesis thus contrasts with findings in the erythroid compartment (see Hofer et al., 1989b) when high numbers of erythroid nuclear cells remained in the spleens of bone marrow recipients until the end of the experiment. On the whole, the influence of repeated bone marrow transplantation on granulopoiesis in the bone marrow and spleen is positive. Of the 22 comparisons made between bone marrow recipients and mice only irradiated, 14 differences are statistically significant, always in favour of bone marrow recipients.