Radioautographic studies on the formation and maturation of bone marrow lymphocytes in mice.

DNA labelling by [3H]thymidine and the sandwich radioimmunolabelling method were used to characterize marrow lymphoid cells and to study the kinetics of production and maturation of small lymphocytes in the bone marrow of adult mice. Marrow lymphoid cells consisted of non-proliferating small lymphocytes, 30-40% of which had detectable surface immunoglobulin (SmIg), and proliferating large lymphoid cells lacking SmIg. Double-labelling experiments employing [3H]thymidine in vivo followed by sandwich radioimmunolabelling in vitro indicated that marrow small lymphocytes lack detectable SmIg when they are formed but develop SmIg within the first few days after production. Marrow lymphocytopoiesis includes; (1) proliferation of large lymphoid cells, which are presumptive small lymphocyte progenitors, which have a cell cycle time of 14-15 hr, and (2) a 3-5 day intramyeloid stage when many newly formed small lymphocytes undergo maturational changes towards the B cell lineage.