Immunoglobulin Synthesis by Human Lymphoid Tissues: Normal Bone Marrow as a Major Site of IgG Production

Abstract The Fab-anti-Fab assay for human IgG quantitation is used to measure in vitro IgG production by lymphocytes from five normal human lymphoid tissues: bone marrow, spleen, blood, lymph node and thymus. Synthesis of IgG was found to proceed at a constant rate over the 10-day culture period; production could be prevented by hypothermia or mitomycin-C. When corrected for total lymphoid cells, the bone marrow was noted to produce greater than 95% of the IgG synthesized by the organs which were evaluated. Secondary antigenic stimulation with smallpox vaccine resulted in accelerated IgG synthesis by blood and splenic lymphocytes; conversely, no response was noted in cultures containing marrow or thymic cells. It is concluded that the bone marrow must be considered as a major site of IgG production under normal circumstances; however, the inability of the bone marrow to respond to antigenic stimulation suggests that the appropriate quantity or quality of cells is lacking in this organ for optimal antigenic recognition and/or processing.