IL-11 DIRECTLY STIMULATES MURINE AND HUMAN ERYTHROID BURST FORMATION IN SEMISOLID CULTURES

The effect of interleukin-11 (IL-11) on cultures of bone marrow cells was investigated. We found that IL-11 increased, in a dose-dependent m anner, the number of bursts in the presence of Epo in murine or human cells cultures. This effect was also observed in cultures of murine ce lls established in serum-free conditions as well as in cultures of CD3 4(+) enriched human cells in serum-containing (but not serum-free) cul tures. A linear relationship between the number of bursts and the plat ed cell number was observed with murine bone marrow cells or non-adher ent mononuclear cells (NA-MNC) human bone marrow cells. Moreover, the effect of IL-11 was not abrogated when either anti-stem cell factor-re ceptor (anti-SCF-R), anti IL-3, or anti-granulocyte/macrophage colony- stimulating factor (GM-CSF), three cytokines known to greatly synergiz e with IL-11, was added to cultures. These results lead us to conclude that IL-11 directly stimulates the proliferation of murine and human burst-forming units-erythroid (BFU-E).