[The modulability of B-lymphocytes on hemopoiesis].

It was confirmed by us previouslythat T cells had an apparent augmenta-tive effects on proliferation of pleuri-potential haemopoietic stem cells andprogenitor cells as well.The presentdata shows a further extensive studyon haemopoiesis the modulability ofisolated B lymphocytes (IBC) whichwere seperated from mouse spleen bymeans of free-flow electrophoresis.IBC consisting of 93.5±1.1% of Ig-FITC(+) cells showed enhancementof proliferation of CFU-S by 4 times ashigh as that of lymph node cells fromathymic nude mice showing 50.9±4.5% of Ig-FITC (+) cells.B cellsproduced 25-fold increment on CFU-S growth as compared with T cellsfrom murine thymus.By the methodof twice-seeding in mice irradiated withsuperlethal dose,IBC also manifestedprofound activity in increasing self-renewal capacity of CFU-S.A largeincrease of colony was detected in cul-ture of GM-CFU 3.8 times as manyas that in control.The supernatantfrom culture of IBC showed markedlyenhancing activities for both CFU-Sin vivo and GM-CFU growth invitro.The data from some other experi-ments suggested that in the superna-tant of activated B cells in culturethere was a kind of modulator whichwas not like CSF but served as astimulator to strengthen CSF-activityin the conditioned medium.The factthat GM-CFU in bone marrow wasreduced significantly by 55% when Blymphocytes were suppressed in vivo byanti-B cell-serum implied a negativemodulation effect of B cells on proli-feration of haemopoietic progenitors. It was assumed that regulation forproliferation of haemopoietic stem cellsmight be the result of interplay betweenstem cells and their surrounding stromacells involving lymphocytes acting asmodulator-producing cells in the mi-croenvironment.