CYTOKINE EXPRESSION AND REGULATION OF HUMAN PLASMA-CELLS - DISAPPEARANCE OF INTERLEUKIN-10 AND PERSISTENCE OF TRANSFORMING GROWTH FACTOR-BETA(1)

Less is known about the cytokine expression and regulation of normal p lasma cells compared to that of activated B cells or myeloma cells. Th is study shows that nonproliferating (hydroxyurea-treated), immunoglob ulin (Ig)-secreting cells generated from human B cells in the EL-4 cul ture system no longer express interleukin (IL)-6 mRNA, progressively l ose LL-10 mRNA, but continue to express transforming growth factor (TG F)-beta(1) mRNA. Secretion of TGF-beta(1) protein was demonstrated. On the other hand, and in contrast to the suppression of B cell prolifer ation and Ig secretion, the basal or the IL-6/IL-10 stimulated Ig secr etion of nonproliferating cells was not inhibited by recombinant TGF-b eta(1). Plasma cells isolated from human bone marrow expressed neither IL-6 nor IL-10 mRNA; only TGF-beta(1) mRNA was detected by reverse tr anscription - polymerase chain reaction analysis. Such plasma cells ma y be on average more ''aged'' cells than those generated in vitro. Thu s, plasma cells persistently express TGF-beta(1), a known suppressor o f various lymphoid and hemopoietic cell activities, but do not limit t heir own Ig secretion via this cytokine.