On the role of thymus in hemopoietic differentiation.

This study was performed to investigate further the connection between the thymus and blood formation suggested by earlier findings. Bone marrow, after in vitro treatment with either anti-thy 1.2 (alpha Thy 1.2) or nonimmune serum and complement, was transplanted to two separate groups of lethally X-irradiated isogenic recipient mice of several different genotypes. Twelve studies were done, and macroscopic spleen-colony numbers were found to be similar in the two groups; however, differences were found when spleens were examined microscopically. The most striking and consistent finding was a decrease in granulopoietic colonies in recipients of alpha-Thy-1.2-treated marrow. There were less pronounced decreases in erythropoietic and in total colonies (all hemopoietic kinds). Ratios of erythropoietic to granulopoietic colonies were regularly increased. Anemia did not develop over a period of 4 months in chimeras given either kind of treated marrow.