Human Bone Marrow Lymphocytes : B and T Cell

Characterization of the different lymphocyte populations in normal human bone marrow (BM) was attempted and compared to that in the peripheral blood (PB). B cells comprised 34% ± 11% of lymphocytes in BM and 23% ± 9% in PB. The majority of B cells carried 1gM in BM and lgG in the PB. In the BM, cells carrying complement or F receptors were fewer than cells carrying Ig, but in the PB they were equal. T cells comprised 6% ± 4% of lymphocytes in the BM and 62% ± 7% in the PB. The majority of BM lymphocytes did not have B or T cell markcr5; these probably included B and T cell precursors. BM lymphocytes carrying surface Ig increased in a 7-day culture, whereas those of the PB decreased. Pokeweed mitogen induced Ig synthesis in B cells of PB but not those of BM. BM-T cells were more efficient than PB-T cells in inhibiting Ig synthesis of PB-B cells. These results indicate that the BM compartment contains immature B cells that are capable of partial differentiation and maturation in vitro. BM-B lymphocytes are probably not involved in the effector phase of the immune response since they are unable to synthesize Ig and because they carry few receptors for complement or F . BM-T lymphocytes are very few and have suppressor capability and therefore may play an essential role in regulation of Ig synthesis by B cells.