Plasma cells represent the final stage of B lymphocyte differentiation. Most plasma cells in secondary lymphoid tissues live for a few days, whereas those in the lamina propria of mucosa and in bone marrow live for several weeks. To investigate the regulation of human plasma cell survival, plasma cells were isolated from tonsils according to high CD38 and low CD20 expression. Tonsillar plasma cells express CD9, CD19, CD24, CD37, CD40, CD74, and HLA-DR, but not CD10, HLA-DQ, CD28, CD56, and Fas/CD95. Although plasma cells express intracytoplasmic Bcl-2, they undergo swift apoptosis in vitro and do not respond to CD40 triggering. Bone marrow fibroblasts and rheumatoid synoviocytes, however, prevented plasma cells from undergoing apoptosis in a contact-dependent fashion. These data indicate that fibroblasts may form a microenvironment favorable for plasma cell survival under normal and pathological conditions.

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