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Functional studies on lymphocytes in adult human bone marrow. I. Immunoglobulin production in vitro after fractionation on a sucrose gradient and T/non-T cell separation.

Bone marrow (BM) was obtained from rib sections removed during thoracotomy on 10 patients (mean age 45 years) with a primary lung tumor. A linear sucrose-serum density gradient was used to fractionate the nucleated bone marrow cells. The pellet fraction, which contained only a few lymphocytes but nearly all the morphologic plasma cells, showed spontaneous IgG and IgM production. The upper fraction (5 to 8% sucrose), comprising 82% lymphoid cells (24.2% T cells and 14.0% B cells (SmIg+ve cells)) showed no spontaneous Ig production, but in five cases produced Ig when stimulated with Pokeweed mitogen (PWM). After T/non-T cell separation of this lymphocyte rich (upper) fraction, the BM-non-T cells produced little or no Ig on their own even when they were stimulated with PWM. However, these cells produced IgM (mean 0.57 μg/ml) and/or IgG (mean 1.69 μg/ml) when cultured with mitomycin-C-treated allogeneic peripheral blood T cells (PB-Tm) and PWM. Parallel cultures of similarly separated PB-non T cells in the presence of PWM and the same PB-Tm produced significantly more Ig (mean IgM 6.02 μg/ml; mean IgG 5.33 μg/ml). When BM-T cells were cultured with PB-non-T cells they appeared to give very poor help for Ig production (IgM mean 0.07 μg/ml, IgG mean 0.27 μg/ml). The results show that bone marrow lymphocytes as judged by Ig production are functionally poor compared with peripheral blood lymphocytes. It seems possible that at least part of the BM-B cells are immature and not able to respond to PWM. The T cells in bone marrow may also be immature or may belong to T cell subpopulations other than helper T cells.