Abstract About 50% of the mouse bone marrow (BM) small lymphocytes bear neither surface immunoglobulin (sIg) nor lymphocyte differentiation antigens (MBLA, MSLA or θ). These “null” lymphocytes are the most newly formed of the BM small lymphocytes. When purified populations of labeled BM null lymphocytes are transfered into syngeneic recipients, they migrate principally to the spleen and 20 hr after transfer about half of them have acquired characteristics of B lymphocytes (sIg, MBLA). After in vitro cultures, a high proportion of these cells acquire sIg and the MBL antigen, a process which does not require cell division. The null lymphocyte population does not contain detectable precursors of T lymphocytes or pluripotential stem cells. The BM B lymphocytes, which appear to derive directly from BM null lymphocytes, differ in several respects from the B lymphocytes found in peripheral lymphoid organs: a number of them bear light chains without detectable µ, γ, or α heavy chains; they have little or no receptor for complement; their response to Escherichia coli lipopolysaccharide in culture is different from that of spleen B lymphocytes.

Ryser, J.-E., & Vassalli, P. (1974). Mouse Bone Marrow Lymphocytes and Their Differentiation. The Journal of Immunology, 113(3), 719–728.